Index: Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationService.cs
===================================================================
diff -u -r9d781268ca54cba6a02715876d34a775396407b5 -ra50f8fe4c13956d52e563e1f9e154f1bd186edad
--- Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationService.cs	(.../PipingCalculationService.cs)	(revision 9d781268ca54cba6a02715876d34a775396407b5)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationService.cs	(.../PipingCalculationService.cs)	(revision a50f8fe4c13956d52e563e1f9e154f1bd186edad)
@@ -106,11 +106,43 @@
         {
             List<string> validationResult = new List<string>();
 
+            var useAssessmentLevelManualInput = inputParameters.UseAssessmentLevelManualInput;
+            var isHydraulicBoundaryLocationMissing = inputParameters.HydraulicBoundaryLocation == null;
             var isSoilProfileMissing = inputParameters.StochasticSoilProfile == null;
             var isSurfaceLineMissing = inputParameters.SurfaceLine == null;
             var isExitPointLMissing = double.IsNaN(inputParameters.ExitPointL);
             var isEntryPointLMissing = double.IsNaN(inputParameters.EntryPointL);
 
+            if (useAssessmentLevelManualInput)
+            {
+                if (double.IsNaN(inputParameters.AssessmentLevel) || double.IsInfinity(inputParameters.AssessmentLevel))
+                {
+                    validationResult.Add(string.Format(RingtoetsCommonServiceResources.Validation_ValidateInput_No_concrete_value_entered_for_ParameterName_0_,
+                                                       ParameterNameExtractor.GetFromDisplayName(RingtoetsCommonFormsResources.AssessmentLevel_DisplayName)));
+                }
+                if (double.IsNaN(inputParameters.PiezometricHeadExit) || double.IsInfinity(inputParameters.PiezometricHeadExit))
+                {
+                    validationResult.Add(Resources.PipingCalculationService_ValidateInput_Cannot_determine_PiezometricHeadExit);
+                }
+            }
+            else
+            {
+                if (isHydraulicBoundaryLocationMissing)
+                {
+                    validationResult.Add(Resources.PipingCalculationService_ValidateInput_No_HydraulicBoundaryLocation_selected);
+                }
+                else
+                {
+                    if (double.IsNaN(inputParameters.AssessmentLevel))
+                    {
+                        validationResult.Add(Resources.PipingCalculationService_ValidateInput_Cannot_determine_AssessmentLevel);
+                    }
+                    if (double.IsNaN(inputParameters.PiezometricHeadExit))
+                    {
+                        validationResult.Add(Resources.PipingCalculationService_ValidateInput_Cannot_determine_PiezometricHeadExit);
+                    }
+                }
+            }
 
             if (isSurfaceLineMissing)
             {
@@ -132,16 +164,6 @@
                 validationResult.Add(Resources.PipingCalculationService_ValidateInput_No_value_for_ExitPointL);
             }
 
-            if (double.IsNaN(inputParameters.AssessmentLevel) || double.IsInfinity(inputParameters.AssessmentLevel))
-            {
-                validationResult.Add(string.Format(RingtoetsCommonServiceResources.Validation_ValidateInput_No_concrete_value_entered_for_ParameterName_0_,
-                                                   ParameterNameExtractor.GetFromDisplayName(RingtoetsCommonFormsResources.AssessmentLevel_DisplayName)));
-            }
-            if (double.IsNaN(inputParameters.PiezometricHeadExit) || double.IsInfinity(inputParameters.PiezometricHeadExit))
-            {
-                validationResult.Add(Resources.PipingCalculationService_ValidateInput_Cannot_determine_PiezometricHeadExit);
-            }
-
             if (!isSurfaceLineMissing && !isSoilProfileMissing && !isExitPointLMissing)
             {
                 if (double.IsNaN(inputParameters.ThicknessAquiferLayer.Mean))