diff --git a/thorlcr/activities/nsplitter/thnsplitterslave.cpp b/thorlcr/activities/nsplitter/thnsplitterslave.cpp
index de22da08908..ca9ccd0d6df 100644
--- a/thorlcr/activities/nsplitter/thnsplitterslave.cpp
+++ b/thorlcr/activities/nsplitter/thnsplitterslave.cpp
@@ -152,7 +152,7 @@ class NSplitterSlaveActivity : public CSlaveActivity, implements ISharedSmartBuf
         }
     }
 public:
-    NSplitterSlaveActivity(CGraphElementBase *_container) : CSlaveActivity(_container), writer(*this)
+    NSplitterSlaveActivity(CGraphElementBase *_container) : CSlaveActivity(_container, nsplitterActivityStatistics), writer(*this)
     {
         numOutputs = container.getOutputs();
         connectedOutputSet.setown(createBitSet());
@@ -401,6 +401,12 @@ class NSplitterSlaveActivity : public CSlaveActivity, implements ISharedSmartBuf
         if (sharedRowStream)
             sharedRowStream->cancel();
     }
+    virtual void gatherActiveStats(CRuntimeStatisticCollection &activeStats) const override
+    {
+        PARENT::gatherActiveStats(activeStats);
+        if (sharedRowStream)
+            ::mergeStats(activeStats, sharedRowStream);
+    }
 // ISharedSmartBufferCallback impl.
     virtual void paged() { pagedOut = true; }
     virtual void blocked()
diff --git a/thorlcr/master/thactivitymaster.cpp b/thorlcr/master/thactivitymaster.cpp
index 82ca2d647a9..f80ee0bd258 100644
--- a/thorlcr/master/thactivitymaster.cpp
+++ b/thorlcr/master/thactivitymaster.cpp
@@ -170,7 +170,6 @@ class CGenericMasterGraphElement : public CMasterGraphElement
             case TAKcase:
             case TAKchildcase:
             case TAKdegroup:
-            case TAKsplit:
             case TAKproject:
             case TAKprefetchproject:
             case TAKprefetchcountproject:
@@ -210,6 +209,9 @@ class CGenericMasterGraphElement : public CMasterGraphElement
             case TAKemptyaction:
                 ret = new CMasterActivity(this);
                 break;
+            case TAKsplit:
+                ret = new CMasterActivity(this, nsplitterActivityStatistics);
+                break;
             case TAKsoap_rowdataset:
             case TAKsoap_rowaction:
             case TAKsoap_datasetdataset:
diff --git a/thorlcr/thorutil/thbuf.cpp b/thorlcr/thorutil/thbuf.cpp
index b1377f6db00..41fb29cb541 100644
--- a/thorlcr/thorutil/thbuf.cpp
+++ b/thorlcr/thorutil/thbuf.cpp
@@ -1753,6 +1753,10 @@ class CSharedWriteAheadBase : public CSimpleInterface, implements ISharedSmartBu
             queryCOutput(c).reset();
         inMemRows->reset(0);
     }
+    virtual unsigned __int64 getStatistic(StatisticKind kind) const override
+    {
+        return 0;
+    }
 friend class COutput;
 friend class CRowSet;
 };
@@ -2145,6 +2149,24 @@ class CSharedWriteAheadDisk : public CSharedWriteAheadBase
         tempFileIO->setSize(0);
         tempFileOwner->noteSize(0);
     }
+    virtual unsigned __int64 getStatistic(StatisticKind kind) const override
+    {
+        switch (kind)
+        {
+            case StSizeSpillFile:
+                return tempFileIO->getStatistic(StSizeDiskWrite);
+            case StCycleDiskWriteIOCycles:
+            case StTimeDiskWriteIO:
+            case StSizeDiskWrite:
+                return 0;
+            case StNumSpills:
+                return 1;
+            case StTimeSpillElapsed:
+                return tempFileIO->getStatistic(StCycleDiskWriteIOCycles);
+            default:
+                return tempFileIO->getStatistic(kind);
+        }
+    }
 };
 
 ISharedSmartBuffer *createSharedSmartDiskBuffer(CActivityBase *activity, const char *spillname, unsigned outputs, IThorRowInterfaces *rowIf)
@@ -2433,7 +2455,7 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
     std::atomic<rowcount_t> totalInputRowsRead = 0; // not used until spilling begins, represents count of all rows read
     rowcount_t inMemTotalRows = 0; // whilst in memory, represents count of all rows seen
     CriticalSection readAheadCS; // ensure single reader (leader), reads ahead (updates rows/totalInputRowsRead/inMemTotalRows)
-    Owned<IFile> iFile;
+    Owned<CFileOwner> tempFileOwner;
     Owned<IFileIO> iFileIO;
     Owned<IBufferedSerialOutputStream> outputStream;
     Linked<ICompressHandler> compressHandler;
@@ -2442,6 +2464,8 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
     bool inputGrouped = false;
     SharedRowStreamReaderOptions options;
     size32_t inMemReadAheadGranularity = 0;
+    CRuntimeStatisticCollection inactiveStats;
+
 
     rowcount_t getLowestOutput()
     {
@@ -2467,13 +2491,19 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
     }
     void closeWriter()
     {
-        iFileIO.clear();
-        outputStream.clear();
+        if (outputStream)
+        {
+            iFileIO->flush();
+            tempFileOwner->noteSize(iFileIO->getStatistic(StSizeDiskWrite));
+            ::mergeStats(inactiveStats, iFileIO);
+            iFileIO.clear();
+            outputStream.clear();
+        }
     }
     void createOutputStream()
     {
         // NB: Called once, when spilling starts.
-        auto res = createSerialOutputStream(iFile, compressHandler, options, numOutputs + 1);
+        auto res = createSerialOutputStream(tempFileOwner->queryIFile(), compressHandler, options, numOutputs + 1);
         outputStream.setown(std::get<0>(res));
         iFileIO.setown(std::get<1>(res));
         totalInputRowsRead = inMemTotalRows;
@@ -2517,7 +2547,7 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
         }
         outputStream->flush();
         totalInputRowsRead.fetch_add(newRowsWritten);
-
+        tempFileOwner->noteSize(iFileIO->getStatistic(StSizeDiskWrite));
         // JCSMORE - could track size written, and start new file at this point (e.g. every 100MB),
         // and track their starting points (by row #) in a vector
         // We could then tell if/when the readers catch up, and remove consumed files as they do.
@@ -2530,7 +2560,8 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
 public:
     explicit CSharedFullSpillingWriteAhead(CActivityBase *_activity, unsigned _numOutputs, IRowStream *_input, bool _inputGrouped, const SharedRowStreamReaderOptions &_options, IThorRowInterfaces *rowIf, const char *tempFileName, ICompressHandler *_compressHandler)
         : activity(*_activity), numOutputs(_numOutputs), input(_input), inputGrouped(_inputGrouped), options(_options), compressHandler(_compressHandler),
-        meta(rowIf->queryRowMetaData()), serializer(rowIf->queryRowSerializer()), allocator(rowIf->queryRowAllocator()), deserializer(rowIf->queryRowDeserializer())
+        meta(rowIf->queryRowMetaData()), serializer(rowIf->queryRowSerializer()), allocator(rowIf->queryRowAllocator()), deserializer(rowIf->queryRowDeserializer()),
+        inactiveStats(spillingWriteAheadStatistics)
     {
         assertex(input);
 
@@ -2541,15 +2572,11 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
 
         for (unsigned o=0; o<numOutputs; o++)
             outputs.push_back(new COutputRowStream(*this, o));
-        iFile.setown(createIFile(tempFileName));
+        tempFileOwner.setown(activity.createOwnedTempFile(tempFileName));
     }
     ~CSharedFullSpillingWriteAhead()
     {
-        if (outputStream) // should have already been closed when inputs all stopped
-        {
-            closeWriter();
-            iFile->remove();
-        }
+        closeWriter();
         freeRows();
     }
     void outputStopped(unsigned output)
@@ -2568,15 +2595,15 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
             {
                 StringBuffer tracing;
                 getFileIOStats(tracing, iFileIO);
-                activity.ActPrintLog("CSharedFullSpillingWriteAhead: removing spill file: %s%s", iFile->queryFilename(), tracing.str());
+                activity.ActPrintLog("CSharedFullSpillingWriteAhead::outputStopped closing tempfile writer: %s %s", tempFileOwner->queryIFile().queryFilename(), tracing.str());
                 closeWriter();
-                iFile->remove();
+                tempFileOwner->noteSize(0);
             }
         }
     }
     std::tuple<IBufferedSerialInputStream *, IFileIO *> getReadStream() // also pass back IFileIO for stats purposes
     {
-        return createSerialInputStream(iFile, compressHandler, options, numOutputs + 1); // +1 for writer
+        return createSerialInputStream(tempFileOwner->queryIFile(), compressHandler, options, numOutputs + 1); // +1 for writer
     }
     bool checkWriteAhead(rowcount_t &outputRowsAvailable)
     {
@@ -2623,7 +2650,7 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
             if (rowsMemUsage >= options.inMemMaxMem) // too much in memory, spill
             {
                 // NB: this will reset rowMemUsage, however, each reader will continue to consume rows until they catch up (or stop)
-                ActPrintLog(&activity, "Spilling to temp storage [file = %s, outputRowsAvailable = %" I64F "u, start = %" I64F "u, end = %" I64F "u, count = %u]", iFile->queryFilename(), outputRowsAvailable, inMemTotalRows - rows.size(), inMemTotalRows, (unsigned)rows.size());
+                ActPrintLog(&activity, "Spilling to temp storage [file = %s, outputRowsAvailable = %" I64F "u, start = %" I64F "u, end = %" I64F "u, count = %u]", tempFileOwner->queryIFile().queryFilename(), outputRowsAvailable, inMemTotalRows - rows.size(), inMemTotalRows, (unsigned)rows.size());
                 createOutputStream();
                 return false;
             }
@@ -2686,11 +2713,8 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
     }
     virtual void reset() override
     {
-        if (outputStream) // should have already been closed when inputs all stopped
-        {
-            closeWriter();
-            iFile->remove();
-        }
+        closeWriter();
+        tempFileOwner->noteSize(0);
         for (auto &output: outputs)
             output->reset();
         freeRows();
@@ -2701,6 +2725,32 @@ class CSharedFullSpillingWriteAhead : public CInterfaceOf<ISharedRowStreamReader
         nextInputReadEog = false;
         endOfInput = false;
     }
+    virtual unsigned __int64 getStatistic(StatisticKind kind) const override
+    {
+        StatisticKind useKind;
+        switch (kind)
+        {
+            case StSizeSpillFile:
+                useKind = StSizeDiskWrite;
+                break;
+            case StCycleDiskWriteIOCycles:
+            case StTimeDiskWriteIO:
+            case StSizeDiskWrite:
+                return 0;
+            case StNumSpills:
+                return 1;
+            case StTimeSpillElapsed:
+                useKind = StCycleDiskWriteIOCycles;
+                break;
+            default:
+                useKind = kind;
+        }
+        unsigned __int64 v = 0;
+        if (likely(iFileIO))
+            v = iFileIO->getStatistic(useKind);
+        v += inactiveStats.getStatisticValue(useKind);
+        return v;
+    }
 };
 
 ISharedRowStreamReader *createSharedFullSpillingWriteAhead(CActivityBase *_activity, unsigned numOutputs, IRowStream *_input, bool _inputGrouped, const SharedRowStreamReaderOptions &options, IThorRowInterfaces *_rowIf, const char *tempFileName, ICompressHandler *compressHandler)
diff --git a/thorlcr/thorutil/thbuf.hpp b/thorlcr/thorutil/thbuf.hpp
index 1750f63b007..fb5a66af8fa 100644
--- a/thorlcr/thorutil/thbuf.hpp
+++ b/thorlcr/thorutil/thbuf.hpp
@@ -87,6 +87,7 @@ interface ISharedRowStreamReader : extends IInterface
     virtual IRowStream *queryOutput(unsigned output) = 0;
     virtual void cancel()=0;
     virtual void reset() = 0;
+    virtual unsigned __int64 getStatistic(StatisticKind kind) const = 0;
 };
 
 
diff --git a/thorlcr/thorutil/thormisc.cpp b/thorlcr/thorutil/thormisc.cpp
index 48dc1231ee1..4d36f2e1686 100644
--- a/thorlcr/thorutil/thormisc.cpp
+++ b/thorlcr/thorutil/thormisc.cpp
@@ -92,8 +92,10 @@ const StatisticsMapping graphStatistics({StNumExecutions, StSizeSpillFile, StSiz
 const StatisticsMapping diskReadPartStatistics({StNumDiskRowsRead}, diskReadRemoteStatistics);
 const StatisticsMapping indexDistribActivityStatistics({}, basicActivityStatistics, jhtreeCacheStatistics);
 const StatisticsMapping soapcallActivityStatistics({}, basicActivityStatistics, soapcallStatistics);
-const StatisticsMapping hashDedupActivityStatistics({StNumSpills, StSizeSpillFile, StTimeSortElapsed, StSizePeakTempDisk}, diskWriteRemoteStatistics, basicActivityStatistics);
+const StatisticsMapping hashDedupActivityStatistics({}, spillStatistics, diskWriteRemoteStatistics, basicActivityStatistics);
 const StatisticsMapping hashDistribActivityStatistics({StNumLocalRows, StNumRemoteRows, StSizeRemoteWrite}, basicActivityStatistics);
+const StatisticsMapping nsplitterActivityStatistics({}, spillStatistics, basicActivityStatistics);
+const StatisticsMapping spillingWriteAheadStatistics({}, spillStatistics);
 
 MODULE_INIT(INIT_PRIORITY_STANDARD)
 {
diff --git a/thorlcr/thorutil/thormisc.hpp b/thorlcr/thorutil/thormisc.hpp
index d760f3d06da..4ba1cc18664 100644
--- a/thorlcr/thorutil/thormisc.hpp
+++ b/thorlcr/thorutil/thormisc.hpp
@@ -166,6 +166,8 @@ extern graph_decl const StatisticsMapping soapcallActivityStatistics;
 extern graph_decl const StatisticsMapping indexReadFileStatistics;
 extern graph_decl const StatisticsMapping hashDedupActivityStatistics;
 extern graph_decl const StatisticsMapping hashDistribActivityStatistics;
+extern graph_decl const StatisticsMapping nsplitterActivityStatistics;
+extern graph_decl const StatisticsMapping spillingWriteAheadStatistics;
 
 class BooleanOnOff
 {