diff --git a/applications/test/parallel-chunks/Test-parallel-chunks.C b/applications/test/parallel-chunks/Test-parallel-chunks.C
index 8c4360cbd9..cbb372298f 100644
--- a/applications/test/parallel-chunks/Test-parallel-chunks.C
+++ b/applications/test/parallel-chunks/Test-parallel-chunks.C
@@ -55,7 +55,7 @@ void do_exchangeBuf
     const bool wait
 )
 {
-    const label startOfRequests = Pstream::nRequests();
+    const label startOfRequests = UPstream::nRequests();
 
     // Set up receives
     // ~~~~~~~~~~~~~~~
@@ -132,7 +132,7 @@ void do_exchangeContainer
     const bool wait
 )
 {
-    const label startOfRequests = Pstream::nRequests();
+    const label startOfRequests = UPstream::nRequests();
 
     // Set up receives
     // ~~~~~~~~~~~~~~~
diff --git a/applications/utilities/preProcessing/mapFieldsPar/MapVolFields.H b/applications/utilities/preProcessing/mapFieldsPar/MapVolFields.H
index 956f90daec..d4f928aed0 100644
--- a/applications/utilities/preProcessing/mapFieldsPar/MapVolFields.H
+++ b/applications/utilities/preProcessing/mapFieldsPar/MapVolFields.H
@@ -43,7 +43,8 @@ void evaluateConstraintTypes(GeometricField<Type, fvPatchField, volMesh>& fld)
 {
     auto& fldBf = fld.boundaryFieldRef();
 
-    const UPstream::commsTypes commsType(UPstream::defaultCommsType);
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+    const label startOfRequests = UPstream::nRequests();
 
     if
     (
@@ -51,8 +52,6 @@ void evaluateConstraintTypes(GeometricField<Type, fvPatchField, volMesh>& fld)
      || commsType == UPstream::commsTypes::nonBlocking
     )
     {
-        const label startOfRequests = UPstream::nRequests();
-
         forAll(fldBf, patchi)
         {
             fvPatchField<Type>& tgtField = fldBf[patchi];
@@ -68,11 +67,7 @@ void evaluateConstraintTypes(GeometricField<Type, fvPatchField, volMesh>& fld)
         }
 
         // Wait for outstanding requests
-        if
-        (
-            UPstream::parRun()
-         && commsType == UPstream::commsTypes::nonBlocking
-        )
+        if (commsType == UPstream::commsTypes::nonBlocking)
         {
             UPstream::waitRequests(startOfRequests);
         }
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/UPstream.H b/src/OpenFOAM/db/IOstreams/Pstreams/UPstream.H
index 2364716736..b884eef604 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/UPstream.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/UPstream.H
@@ -396,19 +396,22 @@ public:
 
         // Non-blocking comms
 
-            //- Get number of outstanding requests
-            static label nRequests();
+            //- Number of outstanding requests
+            static label nRequests() noexcept;
 
-            //- Truncate number of outstanding requests
-            static void resetRequests(const label sz);
+            //- Truncate outstanding requests to given length
+            static void resetRequests(const label n);
 
             //- Wait until all requests (from start onwards) have finished.
+            //  A no-op if parRun() == false
             static void waitRequests(const label start = 0);
 
             //- Wait until request i has finished.
+            //  A no-op if parRun() == false
             static void waitRequest(const label i);
 
             //- Non-blocking comms: has request i finished?
+            //  A no-op and returns true if parRun() == false
             static bool finishedRequest(const label i);
 
             static int allocateTag(const char*);
diff --git a/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricBoundaryField.C b/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricBoundaryField.C
index 21f0336b2e..7daab92e19 100644
--- a/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricBoundaryField.C
+++ b/src/OpenFOAM/fields/GeometricFields/GeometricField/GeometricBoundaryField.C
@@ -437,7 +437,8 @@ void Foam::GeometricBoundaryField<Type, PatchField, GeoMesh>::evaluate()
     ///    InfoInFunction << nl;
     ///}
 
-    const UPstream::commsTypes commsType(UPstream::defaultCommsType);
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+    const label startOfRequests = UPstream::nRequests();
 
     if
     (
@@ -445,19 +446,13 @@ void Foam::GeometricBoundaryField<Type, PatchField, GeoMesh>::evaluate()
      || commsType == UPstream::commsTypes::nonBlocking
     )
     {
-        const label startOfRequests = UPstream::nRequests();
-
         for (auto& pfld : *this)
         {
             pfld.initEvaluate(commsType);
         }
 
         // Wait for outstanding requests
-        if
-        (
-            UPstream::parRun()
-         && commsType == Pstream::commsTypes::nonBlocking
-        )
+        if (commsType == Pstream::commsTypes::nonBlocking)
         {
             UPstream::waitRequests(startOfRequests);
         }
@@ -506,7 +501,8 @@ void Foam::GeometricBoundaryField<Type, PatchField, GeoMesh>::evaluateCoupled()
     ///    InfoInFunction << nl;
     ///}
 
-    const UPstream::commsTypes commsType(UPstream::defaultCommsType);
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+    const label startOfRequests = UPstream::nRequests();
 
     if
     (
@@ -514,8 +510,6 @@ void Foam::GeometricBoundaryField<Type, PatchField, GeoMesh>::evaluateCoupled()
      || commsType == UPstream::commsTypes::nonBlocking
     )
     {
-        const label startOfRequests = UPstream::nRequests();
-
         for (auto& pfld : *this)
         {
             const auto* cpp = isA<CoupledPatchType>(pfld.patch());
@@ -527,11 +521,7 @@ void Foam::GeometricBoundaryField<Type, PatchField, GeoMesh>::evaluateCoupled()
         }
 
         // Wait for outstanding requests
-        if
-        (
-            UPstream::parRun()
-         && commsType == UPstream::commsTypes::nonBlocking
-        )
+        if (commsType == UPstream::commsTypes::nonBlocking)
         {
             UPstream::waitRequests(startOfRequests);
         }
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
index d325e127a1..9061999e69 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
@@ -440,7 +440,7 @@ bool Foam::OFstreamCollator::write
         // Gather all data onto master. Is done in local communicator since
         // not in write thread. Note that we do not store in contiguous
         // buffer since that would limit to 2G chars.
-        const label startOfRequests = Pstream::nRequests();
+        const label startOfRequests = UPstream::nRequests();
         if (Pstream::master(localComm_))
         {
             for (label proci = 1; proci < slaveData.size(); proci++)
@@ -479,7 +479,7 @@ bool Foam::OFstreamCollator::write
                     << Foam::abort(FatalError);
             }
         }
-        Pstream::waitRequests(startOfRequests);
+        UPstream::waitRequests(startOfRequests);
 
         {
             std::lock_guard<std::mutex> guard(mutex_);
diff --git a/src/OpenFOAM/matrices/LduMatrix/LduMatrix/LduMatrixUpdateMatrixInterfaces.C b/src/OpenFOAM/matrices/LduMatrix/LduMatrix/LduMatrixUpdateMatrixInterfaces.C
index 64dd444721..f3679554e8 100644
--- a/src/OpenFOAM/matrices/LduMatrix/LduMatrix/LduMatrixUpdateMatrixInterfaces.C
+++ b/src/OpenFOAM/matrices/LduMatrix/LduMatrix/LduMatrixUpdateMatrixInterfaces.C
@@ -40,10 +40,12 @@ void Foam::LduMatrix<Type, DType, LUType>::initMatrixInterfaces
     Field<Type>& result
 ) const
 {
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+
     if
     (
-        Pstream::defaultCommsType == Pstream::commsTypes::blocking
-     || Pstream::defaultCommsType == Pstream::commsTypes::nonBlocking
+        commsType == UPstream::commsTypes::blocking
+     || commsType == UPstream::commsTypes::nonBlocking
     )
     {
         forAll(interfaces_, interfacei)
@@ -59,12 +61,12 @@ void Foam::LduMatrix<Type, DType, LUType>::initMatrixInterfaces
                     psiif,
                     interfaceCoeffs[interfacei],
                     //Amultiplier<Type, LUType>(interfaceCoeffs[interfacei]),
-                    Pstream::defaultCommsType
+                    commsType
                 );
             }
         }
     }
-    else if (Pstream::defaultCommsType == Pstream::commsTypes::scheduled)
+    else if (commsType == UPstream::commsTypes::scheduled)
     {
         const lduSchedule& patchSchedule = this->patchSchedule();
 
@@ -88,7 +90,7 @@ void Foam::LduMatrix<Type, DType, LUType>::initMatrixInterfaces
                     psiif,
                     interfaceCoeffs[interfacei],
                     //Amultiplier<Type, LUType>(interfaceCoeffs[interfacei]),
-                    Pstream::commsTypes::blocking
+                    UPstream::commsTypes::blocking
                 );
             }
         }
@@ -97,7 +99,7 @@ void Foam::LduMatrix<Type, DType, LUType>::initMatrixInterfaces
     {
         FatalErrorInFunction
             << "Unsupported communications type "
-            << Pstream::commsTypeNames[Pstream::defaultCommsType]
+            << UPstream::commsTypeNames[commsType]
             << exit(FatalError);
     }
 }
@@ -112,17 +114,18 @@ void Foam::LduMatrix<Type, DType, LUType>::updateMatrixInterfaces
     Field<Type>& result
 ) const
 {
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+
     if
     (
-        Pstream::defaultCommsType == Pstream::commsTypes::blocking
-     || Pstream::defaultCommsType == Pstream::commsTypes::nonBlocking
+        commsType == UPstream::commsTypes::blocking
+     || commsType == UPstream::commsTypes::nonBlocking
     )
     {
         // Block until all sends/receives have been finished
-        if (Pstream::defaultCommsType == Pstream::commsTypes::nonBlocking)
+        if (commsType == UPstream::commsTypes::nonBlocking)
         {
-            IPstream::waitRequests();
-            OPstream::waitRequests();
+            UPstream::waitRequests();
         }
 
         forAll(interfaces_, interfacei)
@@ -138,12 +141,12 @@ void Foam::LduMatrix<Type, DType, LUType>::updateMatrixInterfaces
                     psiif,
                     interfaceCoeffs[interfacei],
                     //Amultiplier<Type, LUType>(interfaceCoeffs[interfacei]),
-                    Pstream::defaultCommsType
+                    commsType
                 );
             }
         }
     }
-    else if (Pstream::defaultCommsType == Pstream::commsTypes::scheduled)
+    else if (commsType == UPstream::commsTypes::scheduled)
     {
         const lduSchedule& patchSchedule = this->patchSchedule();
 
@@ -165,7 +168,7 @@ void Foam::LduMatrix<Type, DType, LUType>::updateMatrixInterfaces
                         psiif,
                         interfaceCoeffs[interfacei],
                       //Amultiplier<Type, LUType>(interfaceCoeffs[interfacei]),
-                        Pstream::commsTypes::scheduled
+                        commsType
                     );
                 }
                 else
@@ -179,7 +182,7 @@ void Foam::LduMatrix<Type, DType, LUType>::updateMatrixInterfaces
                         psiif,
                         interfaceCoeffs[interfacei],
                       //Amultiplier<Type, LUType>(interfaceCoeffs[interfacei]),
-                        Pstream::commsTypes::scheduled
+                        commsType
                     );
                 }
             }
@@ -214,7 +217,7 @@ void Foam::LduMatrix<Type, DType, LUType>::updateMatrixInterfaces
     {
         FatalErrorInFunction
             << "Unsupported communications type "
-            << Pstream::commsTypeNames[Pstream::defaultCommsType]
+            << UPstream::commsTypeNames[commsType]
             << exit(FatalError);
     }
 }
diff --git a/src/OpenFOAM/matrices/lduMatrix/lduAddressing/lduInterface/lduCalculatedProcessorField/lduCalculatedProcessorField.C b/src/OpenFOAM/matrices/lduMatrix/lduAddressing/lduInterface/lduCalculatedProcessorField/lduCalculatedProcessorField.C
index 2f78bd8df2..b72ad7e7b8 100644
--- a/src/OpenFOAM/matrices/lduMatrix/lduAddressing/lduInterface/lduCalculatedProcessorField/lduCalculatedProcessorField.C
+++ b/src/OpenFOAM/matrices/lduMatrix/lduAddressing/lduInterface/lduCalculatedProcessorField/lduCalculatedProcessorField.C
@@ -71,7 +71,7 @@ bool Foam::lduCalculatedProcessorField<Type>::ready() const
     if
     (
         this->outstandingSendRequest_ >= 0
-     && this->outstandingSendRequest_ < Pstream::nRequests()
+     && this->outstandingSendRequest_ < UPstream::nRequests()
     )
     {
         if (!UPstream::finishedRequest(this->outstandingSendRequest_))
@@ -84,7 +84,7 @@ bool Foam::lduCalculatedProcessorField<Type>::ready() const
     if
     (
         this->outstandingRecvRequest_ >= 0
-     && this->outstandingRecvRequest_ < Pstream::nRequests()
+     && this->outstandingRecvRequest_ < UPstream::nRequests()
     )
     {
         if (!UPstream::finishedRequest(this->outstandingRecvRequest_))
@@ -210,7 +210,7 @@ void Foam::lduCalculatedProcessorField<Type>::updateInterfaceMatrix
     if
     (
         outstandingRecvRequest_ >= 0
-     && outstandingRecvRequest_ < Pstream::nRequests()
+     && outstandingRecvRequest_ < UPstream::nRequests()
     )
     {
         UPstream::waitRequest(outstandingRecvRequest_);
diff --git a/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixATmul.C b/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixATmul.C
index 2bb8e1ee84..c0e05719fa 100644
--- a/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixATmul.C
+++ b/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixATmul.C
@@ -56,7 +56,7 @@ void Foam::lduMatrix::Amul
     const scalar* const __restrict__ upperPtr = upper().begin();
     const scalar* const __restrict__ lowerPtr = lower().begin();
 
-    const label startRequest = Pstream::nRequests();
+    const label startRequest = UPstream::nRequests();
 
     // Initialise the update of interfaced interfaces
     initMatrixInterfaces
@@ -122,7 +122,7 @@ void Foam::lduMatrix::Tmul
     const scalar* const __restrict__ lowerPtr = lower().begin();
     const scalar* const __restrict__ upperPtr = upper().begin();
 
-    const label startRequest = Pstream::nRequests();
+    const label startRequest = UPstream::nRequests();
 
     // Initialise the update of interfaced interfaces
     initMatrixInterfaces
@@ -246,7 +246,7 @@ void Foam::lduMatrix::residual
     // To compensate for this, it is necessary to turn the
     // sign of the contribution.
 
-    const label startRequest = Pstream::nRequests();
+    const label startRequest = UPstream::nRequests();
 
     // Initialise the update of interfaced interfaces
     initMatrixInterfaces
diff --git a/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixUpdateMatrixInterfaces.C b/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixUpdateMatrixInterfaces.C
index e3c7421c6c..3562159057 100644
--- a/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixUpdateMatrixInterfaces.C
+++ b/src/OpenFOAM/matrices/lduMatrix/lduMatrix/lduMatrixUpdateMatrixInterfaces.C
@@ -40,10 +40,12 @@ void Foam::lduMatrix::initMatrixInterfaces
     const direction cmpt
 ) const
 {
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+
     if
     (
-        Pstream::defaultCommsType == Pstream::commsTypes::blocking
-     || Pstream::defaultCommsType == Pstream::commsTypes::nonBlocking
+        commsType == UPstream::commsTypes::blocking
+     || commsType == UPstream::commsTypes::nonBlocking
     )
     {
         forAll(interfaces, interfacei)
@@ -59,12 +61,12 @@ void Foam::lduMatrix::initMatrixInterfaces
                     psiif,
                     coupleCoeffs[interfacei],
                     cmpt,
-                    Pstream::defaultCommsType
+                    commsType
                 );
             }
         }
     }
-    else if (Pstream::defaultCommsType == Pstream::commsTypes::scheduled)
+    else if (commsType == UPstream::commsTypes::scheduled)
     {
         const lduSchedule& patchSchedule = this->patchSchedule();
 
@@ -88,7 +90,7 @@ void Foam::lduMatrix::initMatrixInterfaces
                     psiif,
                     coupleCoeffs[interfacei],
                     cmpt,
-                    Pstream::commsTypes::blocking
+                    UPstream::commsTypes::blocking
                 );
             }
         }
@@ -97,7 +99,7 @@ void Foam::lduMatrix::initMatrixInterfaces
     {
         FatalErrorInFunction
             << "Unsupported communications type "
-            << Pstream::commsTypeNames[Pstream::defaultCommsType]
+            << UPstream::commsTypeNames[commsType]
             << exit(FatalError);
     }
 }
@@ -114,7 +116,9 @@ void Foam::lduMatrix::updateMatrixInterfaces
     const label startRequest
 ) const
 {
-    if (Pstream::defaultCommsType == Pstream::commsTypes::blocking)
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+
+    if (commsType == UPstream::commsTypes::blocking)
     {
         forAll(interfaces, interfacei)
         {
@@ -129,12 +133,12 @@ void Foam::lduMatrix::updateMatrixInterfaces
                     psiif,
                     coupleCoeffs[interfacei],
                     cmpt,
-                    Pstream::defaultCommsType
+                    commsType
                 );
             }
         }
     }
-    else if (Pstream::defaultCommsType == Pstream::commsTypes::nonBlocking)
+    else if (commsType == UPstream::commsTypes::nonBlocking)
     {
         // Try and consume interfaces as they become available
         bool allUpdated = false;
@@ -160,7 +164,7 @@ void Foam::lduMatrix::updateMatrixInterfaces
                                 psiif,
                                 coupleCoeffs[interfacei],
                                 cmpt,
-                                Pstream::defaultCommsType
+                                commsType
                             );
                         }
                         else
@@ -210,12 +214,12 @@ void Foam::lduMatrix::updateMatrixInterfaces
                     psiif,
                     coupleCoeffs[interfacei],
                     cmpt,
-                    Pstream::defaultCommsType
+                    commsType
                 );
             }
         }
     }
-    else if (Pstream::defaultCommsType == Pstream::commsTypes::scheduled)
+    else if (commsType == UPstream::commsTypes::scheduled)
     {
         const lduSchedule& patchSchedule = this->patchSchedule();
 
@@ -237,7 +241,7 @@ void Foam::lduMatrix::updateMatrixInterfaces
                         psiif,
                         coupleCoeffs[interfacei],
                         cmpt,
-                        Pstream::commsTypes::scheduled
+                        commsType
                     );
                 }
                 else
@@ -251,7 +255,7 @@ void Foam::lduMatrix::updateMatrixInterfaces
                         psiif,
                         coupleCoeffs[interfacei],
                         cmpt,
-                        Pstream::commsTypes::scheduled
+                        commsType
                     );
                 }
             }
@@ -286,7 +290,7 @@ void Foam::lduMatrix::updateMatrixInterfaces
     {
         FatalErrorInFunction
             << "Unsupported communications type "
-            << Pstream::commsTypeNames[Pstream::defaultCommsType]
+            << UPstream::commsTypeNames[commsType]
             << exit(FatalError);
     }
 }
diff --git a/src/OpenFOAM/matrices/lduMatrix/smoothers/GaussSeidel/GaussSeidelSmoother.C b/src/OpenFOAM/matrices/lduMatrix/smoothers/GaussSeidel/GaussSeidelSmoother.C
index a547ad3cb1..5ce88656f3 100644
--- a/src/OpenFOAM/matrices/lduMatrix/smoothers/GaussSeidel/GaussSeidelSmoother.C
+++ b/src/OpenFOAM/matrices/lduMatrix/smoothers/GaussSeidel/GaussSeidelSmoother.C
@@ -115,7 +115,7 @@ void Foam::GaussSeidelSmoother::smooth
     {
         bPrime = source;
 
-        const label startRequest = Pstream::nRequests();
+        const label startRequest = UPstream::nRequests();
 
         matrix_.initMatrixInterfaces
         (
diff --git a/src/OpenFOAM/matrices/lduMatrix/smoothers/nonBlockingGaussSeidel/nonBlockingGaussSeidelSmoother.C b/src/OpenFOAM/matrices/lduMatrix/smoothers/nonBlockingGaussSeidel/nonBlockingGaussSeidelSmoother.C
index 3884e17d19..8f8760fd3a 100644
--- a/src/OpenFOAM/matrices/lduMatrix/smoothers/nonBlockingGaussSeidel/nonBlockingGaussSeidelSmoother.C
+++ b/src/OpenFOAM/matrices/lduMatrix/smoothers/nonBlockingGaussSeidel/nonBlockingGaussSeidelSmoother.C
@@ -142,7 +142,7 @@ void Foam::nonBlockingGaussSeidelSmoother::smooth
     {
         bPrime = source;
 
-        const label startRequest = Pstream::nRequests();
+        const label startRequest = UPstream::nRequests();
 
         matrix_.initMatrixInterfaces
         (
diff --git a/src/OpenFOAM/matrices/lduMatrix/smoothers/symGaussSeidel/symGaussSeidelSmoother.C b/src/OpenFOAM/matrices/lduMatrix/smoothers/symGaussSeidel/symGaussSeidelSmoother.C
index ef3703bc1e..e9e26efa24 100644
--- a/src/OpenFOAM/matrices/lduMatrix/smoothers/symGaussSeidel/symGaussSeidelSmoother.C
+++ b/src/OpenFOAM/matrices/lduMatrix/smoothers/symGaussSeidel/symGaussSeidelSmoother.C
@@ -115,7 +115,7 @@ void Foam::symGaussSeidelSmoother::smooth
     {
         bPrime = source;
 
-        const label startRequest = Pstream::nRequests();
+        const label startRequest = UPstream::nRequests();
 
         matrix_.initMatrixInterfaces
         (
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomerateLduAddressing.C b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomerateLduAddressing.C
index 09b9057ed0..fa64f1db63 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomerateLduAddressing.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGAgglomerations/GAMGAgglomeration/GAMGAgglomerateLduAddressing.C
@@ -272,7 +272,7 @@ void Foam::GAMGAgglomeration::agglomerateLduAddressing
         patchFaceRestrictAddressing_[fineLevelIndex];
 
 
-    const label nReq = Pstream::nRequests();
+    const label startOfRequests = UPstream::nRequests();
 
     // Initialise transfer of restrict addressing on the interface
     // The finest mesh uses patchAddr from the original lduAdressing.
@@ -301,10 +301,7 @@ void Foam::GAMGAgglomeration::agglomerateLduAddressing
         }
     }
 
-    if (Pstream::parRun())
-    {
-        Pstream::waitRequests(nReq);
-    }
+    UPstream::waitRequests(startOfRequests);
 
 
     // Add the coarse level
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/GAMGProcAgglomeration/GAMGProcAgglomeration.C b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/GAMGProcAgglomeration/GAMGProcAgglomeration.C
index 67e8a0335b..48512f5842 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/GAMGProcAgglomeration/GAMGProcAgglomeration.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/GAMGProcAgglomeration/GAMGProcAgglomeration.C
@@ -147,7 +147,7 @@ Foam::labelListList Foam::GAMGProcAgglomeration::globalCellCells
     // Get the interface cells
     PtrList<labelList> nbrGlobalCells(interfaces.size());
     {
-        const label nReq = Pstream::nRequests();
+        const label startOfRequests = UPstream::nRequests();
 
         // Initialise transfer of restrict addressing on the interface
         forAll(interfaces, inti)
@@ -162,10 +162,7 @@ Foam::labelListList Foam::GAMGProcAgglomeration::globalCellCells
             }
         }
 
-        if (UPstream::parRun())
-        {
-            UPstream::waitRequests(nReq);
-        }
+        UPstream::waitRequests(startOfRequests);
 
         forAll(interfaces, inti)
         {
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGSolverInterpolate.C b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGSolverInterpolate.C
index 1620a7b7fe..12eb6b9f94 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGSolverInterpolate.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGSolverInterpolate.C
@@ -52,7 +52,7 @@ void Foam::GAMGSolver::interpolate
     Apsi = 0;
     solveScalar* __restrict__ ApsiPtr = Apsi.begin();
 
-    const label startRequest = Pstream::nRequests();
+    const label startRequest = UPstream::nRequests();
 
     m.initMatrixInterfaces
     (
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/interfaceFields/processorGAMGInterfaceField/processorGAMGInterfaceField.C b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/interfaceFields/processorGAMGInterfaceField/processorGAMGInterfaceField.C
index 0cf63ba1f3..bcc476d840 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/interfaceFields/processorGAMGInterfaceField/processorGAMGInterfaceField.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/interfaceFields/processorGAMGInterfaceField/processorGAMGInterfaceField.C
@@ -169,7 +169,7 @@ void Foam::processorGAMGInterfaceField::updateInterfaceMatrix
         if
         (
             outstandingRecvRequest_ >= 0
-         && outstandingRecvRequest_ < Pstream::nRequests()
+         && outstandingRecvRequest_ < UPstream::nRequests()
         )
         {
             UPstream::waitRequest(outstandingRecvRequest_);
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/PPCG/PPCG.C b/src/OpenFOAM/matrices/lduMatrix/solvers/PPCG/PPCG.C
index dc637b97ce..ec7cb8bb25 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/PPCG/PPCG.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/PPCG/PPCG.C
@@ -170,9 +170,9 @@ Foam::solverPerformance Foam::PPCG::scalarSolveCG
     )
     {
         // Make sure gamma,delta are available
-        if (Pstream::parRun() && outstandingRequest != -1)
+        if (outstandingRequest != -1)
         {
-            Pstream::waitRequest(outstandingRequest);
+            UPstream::waitRequest(outstandingRequest);
             outstandingRequest = -1;
         }
 
@@ -249,9 +249,9 @@ Foam::solverPerformance Foam::PPCG::scalarSolveCG
     }
 
     // Cleanup any outstanding requests
-    if (Pstream::parRun() && outstandingRequest != -1)
+    if (outstandingRequest != -1)
     {
-        Pstream::waitRequest(outstandingRequest);
+        UPstream::waitRequest(outstandingRequest);
     }
 
     return solverPerf;
diff --git a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
index 9099c5c519..5bade23b55 100644
--- a/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
+++ b/src/OpenFOAM/meshes/lduMesh/lduPrimitiveMesh.C
@@ -129,10 +129,8 @@ Foam::labelListList Foam::lduPrimitiveMesh::globalCellCells
             }
         }
 
-        if (Pstream::parRun())
-        {
-            Pstream::waitRequests();
-        }
+        // Wait for all
+        UPstream::waitRequests();
 
         forAll(interfaces, inti)
         {
diff --git a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseSubset.C b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseSubset.C
index e45a2ed0d8..207b6852da 100644
--- a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseSubset.C
+++ b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseSubset.C
@@ -186,8 +186,8 @@ void Foam::mapDistributeBase::exchangeMasks
             }
         }
 
-        // Wait for all to finish
-        Pstream::waitRequests(startOfRequests);
+        // Wait for outstanding requests
+        UPstream::waitRequests(startOfRequests);
     }
 
     // Receiving myself is just a copy
diff --git a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseTemplates.C b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseTemplates.C
index 6580cd3052..6ab2260ce3 100644
--- a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseTemplates.C
+++ b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBaseTemplates.C
@@ -584,8 +584,7 @@ void Foam::mapDistributeBase::distribute
             }
 
 
-            // Wait for all to finish
-
+            // Wait for outstanding requests
             Pstream::waitRequests(nOutstanding);
 
 
@@ -1044,8 +1043,7 @@ void Foam::mapDistributeBase::distribute
             }
 
 
-            // Wait for all to finish
-
+            // Wait for outstanding requests
             Pstream::waitRequests(nOutstanding);
 
 
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
index 33d0a71397..9d594ffd5c 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
@@ -142,7 +142,7 @@ void Foam::globalIndex::gatherValues
 
     if (commsType == UPstream::commsTypes::nonBlocking)
     {
-        // Wait for all to finish
+        // Wait for outstanding requests
         UPstream::waitRequests(startOfRequests);
     }
 }
@@ -242,7 +242,7 @@ void Foam::globalIndex::gather
 
     if (commsType == UPstream::commsTypes::nonBlocking)
     {
-        // Wait for all to finish
+        // Wait for outstanding requests
         UPstream::waitRequests(startOfRequests);
     }
 }
@@ -338,7 +338,7 @@ void Foam::globalIndex::gather
 
     if (commsType == UPstream::commsTypes::nonBlocking)
     {
-        // Wait for all to finish
+        // Wait for outstanding requests
         UPstream::waitRequests(startOfRequests);
     }
 }
@@ -945,7 +945,7 @@ void Foam::globalIndex::scatter
 
     if (commsType == UPstream::commsTypes::nonBlocking)
     {
-        // Wait for all to finish
+        // Wait for outstanding requests
         UPstream::waitRequests(startOfRequests);
     }
 }
diff --git a/src/Pstream/dummy/UPstream.C b/src/Pstream/dummy/UPstream.C
index 5ba1a5330c..a586c1ef1a 100644
--- a/src/Pstream/dummy/UPstream.C
+++ b/src/Pstream/dummy/UPstream.C
@@ -87,13 +87,13 @@ void Foam::UPstream::freePstreamCommunicator(const label)
 {}
 
 
-Foam::label Foam::UPstream::nRequests()
+Foam::label Foam::UPstream::nRequests() noexcept
 {
     return 0;
 }
 
 
-void Foam::UPstream::resetRequests(const label i)
+void Foam::UPstream::resetRequests(const label n)
 {}
 
 
@@ -107,8 +107,7 @@ void Foam::UPstream::waitRequest(const label i)
 
 bool Foam::UPstream::finishedRequest(const label i)
 {
-    NotImplemented;
-    return false;
+    return true;
 }
 
 
diff --git a/src/Pstream/mpi/UPstream.C b/src/Pstream/mpi/UPstream.C
index 87fb171a52..81fdff28ec 100644
--- a/src/Pstream/mpi/UPstream.C
+++ b/src/Pstream/mpi/UPstream.C
@@ -609,23 +609,28 @@ void Foam::UPstream::freePstreamCommunicator(const label communicator)
 }
 
 
-Foam::label Foam::UPstream::nRequests()
+Foam::label Foam::UPstream::nRequests() noexcept
 {
     return PstreamGlobals::outstandingRequests_.size();
 }
 
 
-void Foam::UPstream::resetRequests(const label i)
+void Foam::UPstream::resetRequests(const label n)
 {
-    if (i < PstreamGlobals::outstandingRequests_.size())
+    if (n >= 0 && n < PstreamGlobals::outstandingRequests_.size())
     {
-        PstreamGlobals::outstandingRequests_.setSize(i);
+        PstreamGlobals::outstandingRequests_.resize(n);
     }
 }
 
 
 void Foam::UPstream::waitRequests(const label start)
 {
+    if (!UPstream::parRun())
+    {
+        return;  // No-op for non-parallel
+    }
+
     if (UPstream::debug)
     {
         Pout<< "UPstream::waitRequests : starting wait for "
@@ -672,6 +677,11 @@ void Foam::UPstream::waitRequests(const label start)
 
 void Foam::UPstream::waitRequest(const label i)
 {
+    if (!UPstream::parRun())
+    {
+        return;  // No-op for non-parallel
+    }
+
     if (debug)
     {
         Pout<< "UPstream::waitRequest : starting wait for request:" << i
@@ -717,13 +727,18 @@ void Foam::UPstream::waitRequest(const label i)
 
 bool Foam::UPstream::finishedRequest(const label i)
 {
+    if (!UPstream::parRun())
+    {
+        return true;  // No-op for non-parallel
+    }
+
     if (debug)
     {
         Pout<< "UPstream::finishedRequest : checking request:" << i
             << endl;
     }
 
-    if (i >= PstreamGlobals::outstandingRequests_.size())
+    if (i < 0 || i >= PstreamGlobals::outstandingRequests_.size())
     {
         FatalErrorInFunction
             << "There are " << PstreamGlobals::outstandingRequests_.size()
diff --git a/src/finiteArea/distributed/faMeshDistributorNew.C b/src/finiteArea/distributed/faMeshDistributorNew.C
index 00e433a075..cc6efdd423 100644
--- a/src/finiteArea/distributed/faMeshDistributorNew.C
+++ b/src/finiteArea/distributed/faMeshDistributorNew.C
@@ -305,7 +305,7 @@ Foam::faMeshDistributor::distribute
     // Processor-processor connections
     if (Pstream::parRun())
     {
-        const label startOfRequests = Pstream::nRequests();
+        const label startOfRequests = UPstream::nRequests();
 
         const faBoundaryMesh& oldBndMesh = oldMesh.boundary();
 
@@ -339,8 +339,9 @@ Foam::faMeshDistributor::distribute
             }
         }
 
-        // Wait for all to finish
-        Pstream::waitRequests(startOfRequests);
+        // Wait for outstanding requests
+        // (commsType == UPstream::commsTypes::nonBlocking)
+        UPstream::waitRequests(startOfRequests);
 
         // Receive values
         for (const faPatch& fap : oldBndMesh)
diff --git a/src/finiteArea/faMatrices/faMatrix/faMatrixSolve.C b/src/finiteArea/faMatrices/faMatrix/faMatrixSolve.C
index 63f11d4f81..f718dcf652 100644
--- a/src/finiteArea/faMatrices/faMatrix/faMatrixSolve.C
+++ b/src/finiteArea/faMatrices/faMatrix/faMatrixSolve.C
@@ -111,7 +111,7 @@ Foam::SolverPerformance<Type> Foam::faMatrix<Type>::solve
             PrecisionAdaptor<solveScalar, scalar> sourceCmpt_ss(sourceCmpt);
             ConstPrecisionAdaptor<solveScalar, scalar> psiCmpt_ss(psiCmpt);
 
-            const label startRequest = Pstream::nRequests();
+            const label startRequest = UPstream::nRequests();
 
             initMatrixInterfaces
             (
diff --git a/src/finiteVolume/fields/fvPatchFields/constraint/calculatedProcessor/calculatedProcessorFvPatchField.C b/src/finiteVolume/fields/fvPatchFields/constraint/calculatedProcessor/calculatedProcessorFvPatchField.C
index ba02bd7fa5..08acdaa41b 100644
--- a/src/finiteVolume/fields/fvPatchFields/constraint/calculatedProcessor/calculatedProcessorFvPatchField.C
+++ b/src/finiteVolume/fields/fvPatchFields/constraint/calculatedProcessor/calculatedProcessorFvPatchField.C
@@ -92,7 +92,7 @@ bool Foam::calculatedProcessorFvPatchField<Type>::ready() const
     if
     (
         this->outstandingSendRequest_ >= 0
-     && this->outstandingSendRequest_ < Pstream::nRequests()
+     && this->outstandingSendRequest_ < UPstream::nRequests()
     )
     {
         if (!UPstream::finishedRequest(this->outstandingSendRequest_))
@@ -105,7 +105,7 @@ bool Foam::calculatedProcessorFvPatchField<Type>::ready() const
     if
     (
         this->outstandingRecvRequest_ >= 0
-     && this->outstandingRecvRequest_ < Pstream::nRequests()
+     && this->outstandingRecvRequest_ < UPstream::nRequests()
     )
     {
         if (!UPstream::finishedRequest(this->outstandingRecvRequest_))
@@ -201,7 +201,7 @@ void Foam::calculatedProcessorFvPatchField<Type>::evaluate
         if
         (
             outstandingRecvRequest_ >= 0
-         && outstandingRecvRequest_ < Pstream::nRequests()
+         && outstandingRecvRequest_ < UPstream::nRequests()
         )
         {
             UPstream::waitRequest(outstandingRecvRequest_);
@@ -327,7 +327,7 @@ void Foam::calculatedProcessorFvPatchField<Type>::updateInterfaceMatrix
     if
     (
         outstandingRecvRequest_ >= 0
-     && outstandingRecvRequest_ < Pstream::nRequests()
+     && outstandingRecvRequest_ < UPstream::nRequests()
     )
     {
         UPstream::waitRequest(outstandingRecvRequest_);
diff --git a/src/finiteVolume/fields/fvPatchFields/constraint/processor/processorFvPatchField.C b/src/finiteVolume/fields/fvPatchFields/constraint/processor/processorFvPatchField.C
index 19a38e1804..5d0e817d77 100644
--- a/src/finiteVolume/fields/fvPatchFields/constraint/processor/processorFvPatchField.C
+++ b/src/finiteVolume/fields/fvPatchFields/constraint/processor/processorFvPatchField.C
@@ -283,7 +283,7 @@ void Foam::processorFvPatchField<Type>::evaluate
             if
             (
                 outstandingRecvRequest_ >= 0
-             && outstandingRecvRequest_ < Pstream::nRequests()
+             && outstandingRecvRequest_ < UPstream::nRequests()
             )
             {
                 UPstream::waitRequest(outstandingRecvRequest_);
@@ -416,7 +416,7 @@ void Foam::processorFvPatchField<Type>::updateInterfaceMatrix
         if
         (
             outstandingRecvRequest_ >= 0
-         && outstandingRecvRequest_ < Pstream::nRequests()
+         && outstandingRecvRequest_ < UPstream::nRequests()
         )
         {
             UPstream::waitRequest(outstandingRecvRequest_);
@@ -565,7 +565,7 @@ void Foam::processorFvPatchField<Type>::updateInterfaceMatrix
         if
         (
             outstandingRecvRequest_ >= 0
-         && outstandingRecvRequest_ < Pstream::nRequests()
+         && outstandingRecvRequest_ < UPstream::nRequests()
         )
         {
             UPstream::waitRequest(outstandingRecvRequest_);
@@ -606,11 +606,10 @@ bool Foam::processorFvPatchField<Type>::ready() const
     if
     (
         outstandingSendRequest_ >= 0
-     && outstandingSendRequest_ < Pstream::nRequests()
+     && outstandingSendRequest_ < UPstream::nRequests()
     )
     {
-        bool finished = UPstream::finishedRequest(outstandingSendRequest_);
-        if (!finished)
+        if (!UPstream::finishedRequest(outstandingSendRequest_))
         {
             return false;
         }
@@ -620,11 +619,10 @@ bool Foam::processorFvPatchField<Type>::ready() const
     if
     (
         outstandingRecvRequest_ >= 0
-     && outstandingRecvRequest_ < Pstream::nRequests()
+     && outstandingRecvRequest_ < UPstream::nRequests()
     )
     {
-        bool finished = UPstream::finishedRequest(outstandingRecvRequest_);
-        if (!finished)
+        if (!UPstream::finishedRequest(outstandingRecvRequest_))
         {
             return false;
         }
diff --git a/src/finiteVolume/fvMatrices/fvMatrix/fvMatrixSolve.C b/src/finiteVolume/fvMatrices/fvMatrix/fvMatrixSolve.C
index 5824d665c6..b5188075f0 100644
--- a/src/finiteVolume/fvMatrices/fvMatrix/fvMatrixSolve.C
+++ b/src/finiteVolume/fvMatrices/fvMatrix/fvMatrixSolve.C
@@ -190,7 +190,7 @@ Foam::SolverPerformance<Type> Foam::fvMatrix<Type>::solveSegregated
             PrecisionAdaptor<solveScalar, scalar> sourceCmpt_ss(sourceCmpt);
             ConstPrecisionAdaptor<solveScalar, scalar> psiCmpt_ss(psiCmpt);
 
-            const label startRequest = Pstream::nRequests();
+            const label startRequest = UPstream::nRequests();
 
             initMatrixInterfaces
             (
diff --git a/src/finiteVolume/interpolation/volPointInterpolation/volPointInterpolate.C b/src/finiteVolume/interpolation/volPointInterpolation/volPointInterpolate.C
index 43f77436c1..05a8b628ab 100644
--- a/src/finiteVolume/interpolation/volPointInterpolation/volPointInterpolate.C
+++ b/src/finiteVolume/interpolation/volPointInterpolation/volPointInterpolate.C
@@ -108,6 +108,7 @@ void Foam::volPointInterpolation::addSeparated
     }
 
     // Wait for outstanding requests
+    // (commsType == UPstream::commsTypes::nonBlocking)
     UPstream::waitRequests(startOfRequests);
 
     forAll(pfbf, patchi)
diff --git a/src/functionObjects/field/mapFields/mapFieldsTemplates.C b/src/functionObjects/field/mapFields/mapFieldsTemplates.C
index c5e6968d96..6de7cb7be0 100644
--- a/src/functionObjects/field/mapFields/mapFieldsTemplates.C
+++ b/src/functionObjects/field/mapFields/mapFieldsTemplates.C
@@ -38,7 +38,8 @@ void Foam::functionObjects::mapFields::evaluateConstraintTypes
 {
     auto& fldBf = fld.boundaryFieldRef();
 
-    const UPstream::commsTypes commsType(UPstream::defaultCommsType);
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
+    const label startOfRequests = UPstream::nRequests();
 
     if
     (
@@ -46,8 +47,6 @@ void Foam::functionObjects::mapFields::evaluateConstraintTypes
      || commsType == UPstream::commsTypes::nonBlocking
     )
     {
-        const label startOfRequests = UPstream::nRequests();
-
         forAll(fldBf, patchi)
         {
             fvPatchField<Type>& tgtField = fldBf[patchi];
@@ -63,11 +62,7 @@ void Foam::functionObjects::mapFields::evaluateConstraintTypes
         }
 
         // Wait for outstanding requests
-        if
-        (
-            UPstream::parRun()
-         && commsType == UPstream::commsTypes::nonBlocking
-        )
+        if (commsType == UPstream::commsTypes::nonBlocking)
         {
             UPstream::waitRequests(startOfRequests);
         }
diff --git a/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C b/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
index f77d49d292..823ac8d9cb 100644
--- a/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
+++ b/src/fvAgglomerationMethods/MGridGenGamgAgglomeration/MGridGenGAMGAgglomeration.C
@@ -55,7 +55,7 @@ void Foam::MGridGenGAMGAgglomeration::swap
     PtrList<labelList>& nbrValues
 ) const
 {
-    const label nReq = Pstream::nRequests();
+    const label startOfRequests = UPstream::nRequests();
 
     // Initialise transfer of restrict addressing on the interface
     forAll(interfaces, inti)
@@ -70,10 +70,10 @@ void Foam::MGridGenGAMGAgglomeration::swap
         }
     }
 
-    if (Pstream::parRun())
-    {
-        Pstream::waitRequests(nReq);
-    }
+    // Wait for outstanding requests
+    // (commsType == UPstream::commsTypes::nonBlocking)
+    UPstream::waitRequests(startOfRequests);
+
 
     // Get the interface agglomeration
     nbrValues.setSize(interfaces.size());
diff --git a/src/overset/dynamicOversetFvMesh/dynamicOversetFvMeshTemplates.C b/src/overset/dynamicOversetFvMesh/dynamicOversetFvMeshTemplates.C
index 688913f5dd..7466878bb7 100644
--- a/src/overset/dynamicOversetFvMesh/dynamicOversetFvMeshTemplates.C
+++ b/src/overset/dynamicOversetFvMesh/dynamicOversetFvMeshTemplates.C
@@ -119,22 +119,19 @@ void Foam::dynamicOversetFvMesh::correctBoundaryConditions
     const bool typeOnly
 )
 {
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
     const label startOfRequests = UPstream::nRequests();
 
     forAll(bfld, patchi)
     {
         if (typeOnly == (isA<PatchType>(bfld[patchi]) != nullptr))
         {
-            bfld[patchi].initEvaluate(UPstream::defaultCommsType);
+            bfld[patchi].initEvaluate(commsType);
         }
     }
 
     // Wait for outstanding requests
-    if
-    (
-        UPstream::parRun()
-     && UPstream::defaultCommsType == UPstream::commsTypes::nonBlocking
-    )
+    if (commsType == UPstream::commsTypes::nonBlocking)
     {
         UPstream::waitRequests(startOfRequests);
     }
@@ -143,7 +140,7 @@ void Foam::dynamicOversetFvMesh::correctBoundaryConditions
     {
         if (typeOnly == (isA<PatchType>(bfld[patchi]) != nullptr))
         {
-            bfld[patchi].evaluate(UPstream::defaultCommsType);
+            bfld[patchi].evaluate(commsType);
         }
     }
 }
@@ -903,6 +900,7 @@ void Foam::dynamicOversetFvMesh::correctCoupledBoundaryConditions(GeoField& fld)
 {
     typename GeoField::Boundary& bfld = fld.boundaryFieldRef();
 
+    const UPstream::commsTypes commsType = UPstream::defaultCommsType;
     const label startOfRequests = UPstream::nRequests();
 
     forAll(bfld, patchi)
@@ -910,16 +908,12 @@ void Foam::dynamicOversetFvMesh::correctCoupledBoundaryConditions(GeoField& fld)
         if (bfld[patchi].coupled())
         {
             //Pout<< "initEval of " << bfld[patchi].patch().name() << endl;
-            bfld[patchi].initEvaluate(Pstream::defaultCommsType);
+            bfld[patchi].initEvaluate(commsType);
         }
     }
 
     // Wait for outstanding requests
-    if
-    (
-        UPstream::parRun()
-     && UPstream::defaultCommsType == UPstream::commsTypes::nonBlocking
-    )
+    if (commsType == UPstream::commsTypes::nonBlocking)
     {
         UPstream::waitRequests(startOfRequests);
     }
@@ -929,7 +923,7 @@ void Foam::dynamicOversetFvMesh::correctCoupledBoundaryConditions(GeoField& fld)
         if (bfld[patchi].coupled())
         {
             //Pout<< "eval of " << bfld[patchi].patch().name() << endl;
-            bfld[patchi].evaluate(Pstream::defaultCommsType);
+            bfld[patchi].evaluate(commsType);
         }
     }
 }
diff --git a/src/overset/lduPrimitiveProcessorInterface/GAMG/calculatedProcessorGAMGInterfaceField.C b/src/overset/lduPrimitiveProcessorInterface/GAMG/calculatedProcessorGAMGInterfaceField.C
index 881cd30fdc..8d91292b58 100644
--- a/src/overset/lduPrimitiveProcessorInterface/GAMG/calculatedProcessorGAMGInterfaceField.C
+++ b/src/overset/lduPrimitiveProcessorInterface/GAMG/calculatedProcessorGAMGInterfaceField.C
@@ -171,7 +171,7 @@ void Foam::calculatedProcessorGAMGInterfaceField::updateInterfaceMatrix
         if
         (
             outstandingRecvRequest_ >= 0
-         && outstandingRecvRequest_ < Pstream::nRequests()
+         && outstandingRecvRequest_ < UPstream::nRequests()
         )
         {
             UPstream::waitRequest(outstandingRecvRequest_);
diff --git a/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C b/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
index 2dfa932c4b..6642113b7b 100644
--- a/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
+++ b/src/parallel/decompose/decompositionMethods/metisLikeDecomp/metisLikeDecomp.C
@@ -130,9 +130,9 @@ Foam::label Foam::metisLikeDecomp::decomposeGeneral
         }
     }
 
+    // Wait for outstanding requests
     if (commsType == UPstream::commsTypes::nonBlocking)
     {
-        // Wait for all to finish
         UPstream::waitRequests(startOfRequests);
     }