Merge pull request #13864 from mantidproject/13852_waterfall_option_not_working_when_reusing_window

MantidPlot/src/Mantid/MantidUI.cpp

@@ -3129,7 +3129,8 @@ MultiLayer* MantidUI::plot1D(const QMultiMap<QString,int>& toPlot, bool spectrum
     if (ask.clickedButton() != confirmButton) return NULL;
   }
   // Force waterfall option to false if only 1 curve
-  if(toPlot.size() == 1) waterfallPlot = false;
+  if ((NULL == plotWindow || clearWindow == true) && toPlot.size() == 1)
+    waterfallPlot = false;
 
   QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));