Index: Wti.Calculation.TestUtil/TestPipingOutput.cs
===================================================================
diff -u
--- Wti.Calculation.TestUtil/TestPipingOutput.cs	(revision 0)
+++ Wti.Calculation.TestUtil/TestPipingOutput.cs	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -0,0 +1,9 @@
+using Wti.Data;
+
+namespace Wti.Calculation.Test.Piping.Stub
+{
+    public class TestPipingOutput : PipingOutput
+    {
+        public TestPipingOutput() : base(0, 0, 0, 0, 0, 0) {}
+    }
+}
\ No newline at end of file
Index: Wti.Calculation.TestUtil/Wti.Calculation.TestUtil.csproj
===================================================================
diff -u -ra3b93c36c2051bd6112327bff0d836ae7883737d -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- Wti.Calculation.TestUtil/Wti.Calculation.TestUtil.csproj	(.../Wti.Calculation.TestUtil.csproj)	(revision a3b93c36c2051bd6112327bff0d836ae7883737d)
+++ Wti.Calculation.TestUtil/Wti.Calculation.TestUtil.csproj	(.../Wti.Calculation.TestUtil.csproj)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -41,6 +41,7 @@
   <ItemGroup>
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="TestPipingInput.cs" />
+    <Compile Include="TestPipingOutput.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\src\Plugins\Wti\Wti.Calculation\Wti.Calculation.csproj">
Index: src/Plugins/Wti/Wti.Data/PipingFailureMechanism.cs
===================================================================
diff -u -r325410362b50750d3c291d19c1526799c9b1c583 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Data/PipingFailureMechanism.cs	(.../PipingFailureMechanism.cs)	(revision 325410362b50750d3c291d19c1526799c9b1c583)
+++ src/Plugins/Wti/Wti.Data/PipingFailureMechanism.cs	(.../PipingFailureMechanism.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -1,13 +1,16 @@
 using System.Collections.Generic;
 using System.Linq;
+using DelftTools.Shell.Core;
 
 namespace Wti.Data
 {
     /// <summary>
     /// Model for performing piping calculations.
     /// </summary>
-    public class PipingFailureMechanism
+    public class PipingFailureMechanism : IObservable
     {
+        private readonly IList<IObserver> observers = new List<IObserver>();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PipingFailureMechanism"/> class.
         /// </summary>
@@ -26,5 +29,23 @@
         /// Gets the input data which contains input and output of a piping calculation
         /// </summary>
         public PipingData PipingData { get; set; }
+
+        public void Attach(IObserver observer)
+        {
+            observers.Add(observer);
+        }
+
+        public void Detach(IObserver observer)
+        {
+            observers.Remove(observer);
+        }
+
+        public void NotifyObservers()
+        {
+            foreach (var observer in observers)
+            {
+                observer.UpdateObserver();
+            }
+        }
     }
 }
\ No newline at end of file
Index: src/Plugins/Wti/Wti.Forms/NodePresenters/PipingContextMenuStrip.cs
===================================================================
diff -u -r325410362b50750d3c291d19c1526799c9b1c583 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Forms/NodePresenters/PipingContextMenuStrip.cs	(.../PipingContextMenuStrip.cs)	(revision 325410362b50750d3c291d19c1526799c9b1c583)
+++ src/Plugins/Wti/Wti.Forms/NodePresenters/PipingContextMenuStrip.cs	(.../PipingContextMenuStrip.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -18,15 +18,25 @@
         public Action<PipingData> OnCalculationClick { get; set; }
 
         /// <summary>
+        /// Gets or sets the <see cref="Action"/> which is performed when the validate item on a <see cref="PipingContextMenuStrip"/> is called.
+        /// </summary>
+        public Action<PipingData> OnValidationClick { get; set; }
+
+        /// <summary>
         /// Creates a new instance of <see cref="PipingContextMenuStrip"/> and assigns the <see cref="PipingData"/> to it.
         /// </summary>
         /// <param name="pipingData"></param>
         public PipingContextMenuStrip(PipingData pipingData)
         {
             this.pipingData = pipingData;
+
+            var validateItem = new ToolStripMenuItem(Resources.PipingDataContextMenuValidate);
+            validateItem.Click += ValidateItemClick;
+
             var calculateItem = new ToolStripMenuItem(Resources.PipingDataContextMenuCalculate);
             calculateItem.Click += CalculateItemClick;
-            Items.Add(calculateItem);
+
+            Items.AddRange(new ToolStripItem[] { validateItem, calculateItem });
         }
 
         private void CalculateItemClick(object sender, EventArgs e)
@@ -36,5 +46,13 @@
                 OnCalculationClick(pipingData);
             }
         }
+
+        private void ValidateItemClick(object sender, EventArgs e)
+        {
+            if (OnValidationClick != null)
+            {
+                OnValidationClick(pipingData);
+            }
+        }
     }
 }
\ No newline at end of file
Index: src/Plugins/Wti/Wti.Forms/NodePresenters/PipingDataNodePresenter.cs
===================================================================
diff -u -r1689206627a4343d07fafcebb0a931b7a0e9e2d2 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Forms/NodePresenters/PipingDataNodePresenter.cs	(.../PipingDataNodePresenter.cs)	(revision 1689206627a4343d07fafcebb0a931b7a0e9e2d2)
+++ src/Plugins/Wti/Wti.Forms/NodePresenters/PipingDataNodePresenter.cs	(.../PipingDataNodePresenter.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -5,7 +5,6 @@
 using DelftTools.Controls.Swf;
 using DelftTools.Utils.Collections;
 using log4net;
-using Wti.Calculation.Piping;
 using Wti.Data;
 using Wti.Forms.Properties;
 using Wti.Service;
@@ -78,25 +77,15 @@
 
         public IMenuItem GetContextMenu(ITreeNode sender, object nodeData)
         {
-            var contextMenu = new PipingContextMenuStrip((PipingData)nodeData);
+            var contextMenu = new PipingContextMenuStrip((PipingData) nodeData);
             var contextMenuAdapter = new MenuItemContextMenuStripAdapter(contextMenu);
 
             contextMenu.OnCalculationClick += PerformPipingCalculation;
+            contextMenu.OnValidationClick += PerformPipingValidation;
 
             return contextMenuAdapter;
         }
 
-        private void PerformPipingCalculation(PipingData pipingData)
-        {
-            var calculationErrorMessages = PipingCalculationService.PerfromValidatedCalculation(pipingData);
-
-            foreach(var errorMessage in calculationErrorMessages) 
-            {
-                LogManager.GetLogger(typeof(PipingData)).Error(String.Format(Resources.ErrorInPipingCalculation_0, errorMessage));
-            }
-            pipingData.NotifyObservers();
-        }
-
         public void OnPropertyChanged(object sender, ITreeNode node, PropertyChangedEventArgs e) {}
 
         public void OnCollectionChanged(object sender, NotifyCollectionChangingEventArgs e) {}
@@ -113,5 +102,16 @@
             failureMechanism.PipingData = null;
             return true;
         }
+
+        private void PerformPipingValidation(PipingData pipingData)
+        {
+            PipingCalculationService.Validate(pipingData);
+        }
+
+        private void PerformPipingCalculation(PipingData pipingData)
+        {
+            PipingCalculationService.PerfromValidatedCalculation(pipingData);
+            pipingData.NotifyObservers();
+        }
     }
 }
\ No newline at end of file
Index: src/Plugins/Wti/Wti.Forms/NodePresenters/PipingOutputNodePresenter.cs
===================================================================
diff -u -r5fc71a385897af92ccb092f2f969b5709afab85a -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Forms/NodePresenters/PipingOutputNodePresenter.cs	(.../PipingOutputNodePresenter.cs)	(revision 5fc71a385897af92ccb092f2f969b5709afab85a)
+++ src/Plugins/Wti/Wti.Forms/NodePresenters/PipingOutputNodePresenter.cs	(.../PipingOutputNodePresenter.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -75,7 +75,7 @@
 
         public bool CanRemove(object parentNodeData, object nodeData)
         {
-            return true;
+            return false;
         }
 
         public bool RemoveNodeData(object parentNodeData, object nodeData)
Index: src/Plugins/Wti/Wti.Forms/Properties/Resources.Designer.cs
===================================================================
diff -u -rbb61ed227cf79e994b84019096e4297b2fbd4527 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Forms/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision bb61ed227cf79e994b84019096e4297b2fbd4527)
+++ src/Plugins/Wti/Wti.Forms/Properties/Resources.Designer.cs	(.../Resources.Designer.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -79,15 +79,6 @@
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Piping berekening niet gelukt: {0}.
-        /// </summary>
-        public static string ErrorInPipingCalculation_0 {
-            get {
-                return ResourceManager.GetString("ErrorInPipingCalculation_0", resourceCulture);
-            }
-        }
-        
-        /// <summary>
         ///   Looks up a localized resource of type System.Drawing.Bitmap.
         /// </summary>
         public static System.Drawing.Bitmap FolderIcon {
@@ -171,6 +162,15 @@
         }
         
         /// <summary>
+        ///   Looks up a localized string similar to Valideren.
+        /// </summary>
+        public static string PipingDataContextMenuValidate {
+            get {
+                return ResourceManager.GetString("PipingDataContextMenuValidate", resourceCulture);
+            }
+        }
+        
+        /// <summary>
         ///   Looks up a localized string similar to Kritiek verhang met betrekking tot heave..
         /// </summary>
         public static string PipingDataCriticalHeaveGradientDescription {
Index: src/Plugins/Wti/Wti.Forms/Properties/Resources.resx
===================================================================
diff -u -rbb61ed227cf79e994b84019096e4297b2fbd4527 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Forms/Properties/Resources.resx	(.../Resources.resx)	(revision bb61ed227cf79e994b84019096e4297b2fbd4527)
+++ src/Plugins/Wti/Wti.Forms/Properties/Resources.resx	(.../Resources.resx)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -334,8 +334,8 @@
   <data name="AddPipingFailureMechanismContextMenuItem" xml:space="preserve">
     <value>Voeg piping faalmechanisme toe</value>
   </data>
-  <data name="ErrorInPipingCalculation_0" xml:space="preserve">
-    <value>Piping berekening niet gelukt: {0}</value>
+  <data name="PipingDataContextMenuValidate" xml:space="preserve">
+    <value>Valideren</value>
   </data>
   <data name="ImportIcon" type="System.Resources.ResXFileRef, System.Windows.Forms">
     <value>..\Resources\table-import.png;System.Drawing.Bitmap, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
Index: src/Plugins/Wti/Wti.Service/DateTimeService.cs
===================================================================
diff -u
--- src/Plugins/Wti/Wti.Service/DateTimeService.cs	(revision 0)
+++ src/Plugins/Wti/Wti.Service/DateTimeService.cs	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -0,0 +1,21 @@
+using System;
+
+namespace Wti.Service
+{
+    /// <summary>
+    /// The <see cref="DateTimeService"/> class is responsible for providing general <see cref="DateTime"/> operations.
+    /// </summary>
+    public static class DateTimeService
+    {
+        /// <summary>
+        /// Gets the current time in HH:mm:ss format.
+        /// </summary>
+        public static String CurrentTimeAsString
+        {
+            get
+            {
+                return DateTime.Now.ToString("HH:mm:ss");
+            }
+        }
+    }
+}
\ No newline at end of file
Index: src/Plugins/Wti/Wti.Service/PipingCalculationResult.cs
===================================================================
diff -u
--- src/Plugins/Wti/Wti.Service/PipingCalculationResult.cs	(revision 0)
+++ src/Plugins/Wti/Wti.Service/PipingCalculationResult.cs	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -0,0 +1,23 @@
+namespace Wti.Service
+{
+    /// <summary>
+    /// Status result from a calculation or validation performed by the <see cref="PipingCalculationService"/>.
+    /// </summary>
+    public enum PipingCalculationResult
+    {
+        /// <summary>
+        /// Value which is returned when no calculation or validation errors occurred.
+        /// </summary>
+        Successful,
+
+        /// <summary>
+        /// Value which is returned when the validation routine resulted in validation errors.
+        /// </summary>
+        ValidationErrors,
+
+        /// <summary>
+        /// Value which is returned when the calculation routine encountered problems.
+        /// </summary>
+        CalculationErrors
+    }
+}
\ No newline at end of file
Index: src/Plugins/Wti/Wti.Service/PipingCalculationService.cs
===================================================================
diff -u -r1689206627a4343d07fafcebb0a931b7a0e9e2d2 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Service/PipingCalculationService.cs	(.../PipingCalculationService.cs)	(revision 1689206627a4343d07fafcebb0a931b7a0e9e2d2)
+++ src/Plugins/Wti/Wti.Service/PipingCalculationService.cs	(.../PipingCalculationService.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -1,66 +1,101 @@
-using System.Collections.Generic;
+using System;
+using log4net;
 using Wti.Calculation.Piping;
 using Wti.Data;
+using Wti.Service.Properties;
 
 namespace Wti.Service
 {
     /// <summary>
-    /// This class controls the <see cref="PipingData"/> and its PipingDataNodePresenter.
-    /// Interactions from the PipingDataNodePresenter are handles by this class.
+    /// This class is responsible for invoking operations on the <see cref="PipingCalculation"/>. Error and status information is 
+    /// logged during the execution of the operation. At the end of an operation, a <see cref="PipingCalculationResult"/> is returned,
+    /// representing the result of the operation.
     /// </summary>
     public static class PipingCalculationService
     {
+        private static readonly ILog PipingDataLogger = LogManager.GetLogger(typeof(PipingData));
+
         /// <summary>
         /// Performs a piping calculation based on the supplied <see cref="PipingData"/> and sets <see cref="PipingData.Output"/>
-        /// to the <see cref="PipingCalculationResult"/> if the calculation was successful.
+        /// to the <see cref="PipingCalculationResult"/> if the calculation was successful. Error and status information is logged during
+        /// the execution of the operation.
         /// </summary>
         /// <param name="pipingData">The <see cref="PipingData"/> to base the input for the calculation upon.</param>
-        /// <returns>A <see cref="List{T}"/> with all the messages that were returned due to validation errors in the given <paramref name="pipingData"/>
-        /// or error message that occurred when performing the calculation.</returns>
-        public static List<string> PerfromValidatedCalculation(PipingData pipingData)
+        /// <returns>If <paramref name="pipingData"/> contains validation errors, then <see cref="PipingCalculationResult.ValidationErrors"/> is returned.
+        /// If problems were encountered during the calculation, <see cref="PipingCalculationResult.CalculationErrors"/> is returned. 
+        /// Otherwise, <see cref="PipingCalculationResult.Successful"/> is returned.</returns>
+        public static PipingCalculationResult PerfromValidatedCalculation(PipingData pipingData)
         {
-            var validationResults = Validate(pipingData);
-            if (validationResults.Count > 0)
+            PipingCalculationResult validationResult = Validate(pipingData);
+
+            if (validationResult == PipingCalculationResult.Successful)
             {
                 ClearOutput(pipingData);
-                return validationResults;
+                return Calculate(pipingData);
             }
-            try
+
+            return validationResult;
+        }
+
+        /// <summary>
+        /// Performs validation over the values on the given <paramref name="pipingData"/>. Error and status information is logged during
+        /// the execution of the operation.
+        /// </summary>
+        /// <param name="pipingData">The <see cref="PipingData"/> for which to validate the values.</param>
+        /// <returns>If <paramref name="pipingData"/> contains validation errors, then <see cref="PipingCalculationResult.ValidationErrors"/> is returned.
+        /// Otherwise, <see cref="PipingCalculationResult.Successful"/> is returned.</returns>
+        public static PipingCalculationResult Validate(PipingData pipingData)
+        {
+            PipingDataLogger.Info(String.Format(Resources.ValidationStarted_0, DateTimeService.CurrentTimeAsString));
+
+            var validationResults = new PipingCalculation(CreateInputFromData(pipingData)).Validate();
+            LogMessagesAsError(validationResults.ToArray());
+
+            PipingDataLogger.Info(String.Format(Resources.ValidationEnded_0, DateTimeService.CurrentTimeAsString));
+
+            return validationResults.Count > 0 ? PipingCalculationResult.ValidationErrors : PipingCalculationResult.Successful;
+        }
+
+        private static void LogMessagesAsError(params string[] errorMessages)
+        {
+            foreach (var errorMessage in errorMessages)
             {
-                Calculate(pipingData);
+                PipingDataLogger.Error(string.Format(Resources.ErrorInPipingCalculation_0, errorMessage));
             }
-            catch (PipingCalculationException e)
-            {
-                ClearOutput(pipingData);
-                return new List<string>{ e.Message };
-            }
-            return new List<string>();
         }
 
         private static void ClearOutput(PipingData pipingData)
         {
             pipingData.Output = null;
         }
 
-        private static void Calculate(PipingData pipingData)
+        private static PipingCalculationResult Calculate(PipingData pipingData)
         {
-            var input = CreateInputFromData(pipingData);
-            var pipingCalculation = new PipingCalculation(input);
+            PipingDataLogger.Info(String.Format(Resources.CalculationStarted_0, DateTimeService.CurrentTimeAsString));
 
-            var pipingResult = pipingCalculation.Calculate();
+            try
+            {
+                var pipingResult = new PipingCalculation(CreateInputFromData(pipingData)).Calculate();
 
-            pipingData.Output = new PipingOutput(pipingResult.UpliftZValue,
-                                                 pipingResult.UpliftFactorOfSafety,
-                                                 pipingResult.HeaveZValue, pipingResult.HeaveFactorOfSafety, pipingResult.SellmeijerZValue, pipingResult.SellmeijerFactorOfSafety);
+                pipingData.Output = new PipingOutput(pipingResult.UpliftZValue,
+                                                     pipingResult.UpliftFactorOfSafety,
+                                                     pipingResult.HeaveZValue,
+                                                     pipingResult.HeaveFactorOfSafety,
+                                                     pipingResult.SellmeijerZValue,
+                                                     pipingResult.SellmeijerFactorOfSafety);
+            }
+            catch (PipingCalculationException e)
+            {
+                LogMessagesAsError(e.Message);
+                return PipingCalculationResult.CalculationErrors;
+            }
+            finally
+            {
+                PipingDataLogger.Info(String.Format(Resources.CalculationEnded_0, DateTimeService.CurrentTimeAsString));
+            }
+            return PipingCalculationResult.Successful;
         }
 
-        public static List<string> Validate(PipingData pipingData)
-        {
-            var input = CreateInputFromData(pipingData);
-
-            return new PipingCalculation(input).Validate();
-        } 
-
         private static PipingCalculationInput CreateInputFromData(PipingData pipingData)
         {
             return new PipingCalculationInput(
Fisheye: Tag 82e08784e174b6b2799fc19cc04e7d7aeb7b84e9 refers to a dead (removed) revision in file `src/Plugins/Wti/Wti.Service/Properties/Resources.Designer.cs'.
Fisheye: No comparison available.  Pass `N' to diff?
Fisheye: Tag 82e08784e174b6b2799fc19cc04e7d7aeb7b84e9 refers to a dead (removed) revision in file `src/Plugins/Wti/Wti.Service/Properties/Resources.resx'.
Fisheye: No comparison available.  Pass `N' to diff?
Index: src/Plugins/Wti/Wti.Service/Wti.Service.csproj
===================================================================
diff -u -r82e08784e174b6b2799fc19cc04e7d7aeb7b84e9 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- src/Plugins/Wti/Wti.Service/Wti.Service.csproj	(.../Wti.Service.csproj)	(revision 82e08784e174b6b2799fc19cc04e7d7aeb7b84e9)
+++ src/Plugins/Wti/Wti.Service/Wti.Service.csproj	(.../Wti.Service.csproj)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -53,8 +53,15 @@
     <Compile Include="..\..\..\GlobalAssembly.cs">
       <Link>Properties\GlobalAssembly.cs</Link>
     </Compile>
+    <Compile Include="DateTimeService.cs" />
+    <Compile Include="PipingCalculationResult.cs" />
     <Compile Include="PipingCalculationService.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Properties\Resources.Designer.cs">
+      <AutoGen>True</AutoGen>
+      <DesignTime>True</DesignTime>
+      <DependentUpon>Resources.resx</DependentUpon>
+    </Compile>
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\Common\DelftTools.Controls.Swf\DelftTools.Controls.Swf.csproj">
@@ -82,6 +89,12 @@
       <Name>Wti.Data</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Properties\Resources.resx">
+      <Generator>ResXFileCodeGenerator</Generator>
+      <LastGenOutput>Resources.Designer.cs</LastGenOutput>
+    </EmbeddedResource>
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>
     <PreBuildEvent>
Index: test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingDataNodePresenterTest.cs
===================================================================
diff -u -r1689206627a4343d07fafcebb0a931b7a0e9e2d2 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingDataNodePresenterTest.cs	(.../PipingDataNodePresenterTest.cs)	(revision 1689206627a4343d07fafcebb0a931b7a0e9e2d2)
+++ test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingDataNodePresenterTest.cs	(.../PipingDataNodePresenterTest.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -271,8 +271,9 @@
 
             // Assert
             Assert.NotNull(contextMenu);
-            Assert.AreEqual(1, contextMenu.ContextMenuStrip.Items.Count);
-            Assert.AreEqual(WtiFormsResources.PipingDataContextMenuCalculate, contextMenu.ContextMenuStrip.Items[0].Text);
+            Assert.AreEqual(2, contextMenu.ContextMenuStrip.Items.Count);
+            Assert.AreEqual(WtiFormsResources.PipingDataContextMenuCalculate, contextMenu.ContextMenuStrip.Items[1].Text);
+            Assert.AreEqual(WtiFormsResources.PipingDataContextMenuValidate, contextMenu.ContextMenuStrip.Items[0].Text);
             Assert.IsInstanceOf<PipingContextMenuStrip>(contextMenu.ContextMenuStrip);
             mocks.VerifyAll(); // Expect no calls on arguments
         }
@@ -356,6 +357,11 @@
         public void GivenInvalidPipingData_WhenCalculatingFromContextMenu_ThenPipingDataNotifiesObserversAndLogMessageAdded()
         {
             // Given
+            var expectedValidationMessageCount = 6;
+            var expectedStatusMessageCount = 2;
+            var expectedLogMessageCount = expectedValidationMessageCount + expectedStatusMessageCount;
+
+            var calculateContextMenuItemIndex = 1;
             var pipingData = new PipingData();
             var observer = mockRepository.StrictMock<IObserver>();
             var nodePresenter = new PipingDataNodePresenter();
@@ -367,18 +373,50 @@
             var contextMenuAdapter = nodePresenter.GetContextMenu(null, pipingData) as MenuItemContextMenuStripAdapter;
             
             // When
-            Action action = () => contextMenuAdapter.ContextMenuStrip.Items[0].PerformClick();
+            Action action = () => contextMenuAdapter.ContextMenuStrip.Items[calculateContextMenuItemIndex].PerformClick();
 
             // Then
-            TestHelper.AssertLogMessagesCount(action, 6);
+            TestHelper.AssertLogMessagesCount(action, expectedLogMessageCount);
             Assert.IsNull(pipingData.Output);
             mockRepository.VerifyAll();
         }
 
         [Test]
+        public void GivenInvalidPipingData_WhenValidatingFromContextMenu_ThenLogMessageAddedAndNoNotifyObserver()
+        {
+            // Given
+            var expectedValidationMessageCount = 6;
+            var expectedStatusMessageCount = 2;
+            var expectedLogMessageCount = expectedValidationMessageCount + expectedStatusMessageCount;
+
+            var validateContextMenuItemIndex = 0;
+            var pipingData = new PipingData();
+            var observer = mockRepository.StrictMock<IObserver>();
+            var nodePresenter = new PipingDataNodePresenter();
+            observer.Expect(o => o.UpdateObserver()).Repeat.Never();
+            pipingData.Attach(observer);
+
+            mockRepository.ReplayAll();
+
+            var contextMenuAdapter = nodePresenter.GetContextMenu(null, pipingData) as MenuItemContextMenuStripAdapter;
+
+            // When
+            Action action = () => contextMenuAdapter.ContextMenuStrip.Items[validateContextMenuItemIndex].PerformClick();
+
+            // Then
+            TestHelper.AssertLogMessagesCount(action, expectedLogMessageCount);
+            mockRepository.VerifyAll();
+        }
+
+        [Test]
         public void GivenValidPipingData_WhenCalculatingFromContextMenu_ThenPipingDataNotifiesObservers()
         {
             // Given
+            var expectedCalculationStatusMessageCount = 2;
+            var expectedValidationStatusMessageCount = 2;
+            var expectedLogMessageCount = expectedCalculationStatusMessageCount + expectedValidationStatusMessageCount;
+
+            var calculateContextMenuItemIndex = 1;
             var pipingData = new PipingData();
             var validPipingInput = new TestPipingInput();
             pipingData.AssessmentLevel = validPipingInput.AssessmentLevel;
@@ -414,10 +452,10 @@
             var contextMenuAdapter = nodePresenter.GetContextMenu(null, pipingData) as MenuItemContextMenuStripAdapter;
 
             // When
-            Action action = () => contextMenuAdapter.ContextMenuStrip.Items[0].PerformClick();
+            Action action = () => contextMenuAdapter.ContextMenuStrip.Items[calculateContextMenuItemIndex].PerformClick();
 
             // Then
-            TestHelper.AssertLogMessagesCount(action, 0);
+            TestHelper.AssertLogMessagesCount(action, expectedLogMessageCount);
             Assert.IsNotNull(pipingData.Output);
             mockRepository.VerifyAll();
         }
Index: test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingOutputNodePresenterTest.cs
===================================================================
diff -u -rad18963162aaa0d4f16d583f2bd8b51480e1e1ba -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingOutputNodePresenterTest.cs	(.../PipingOutputNodePresenterTest.cs)	(revision ad18963162aaa0d4f16d583f2bd8b51480e1e1ba)
+++ test/Plugins/Wti/Wti.Forms.Test/NodePresenters/PipingOutputNodePresenterTest.cs	(.../PipingOutputNodePresenterTest.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -4,6 +4,7 @@
 using DelftTools.Utils.Collections;
 using NUnit.Framework;
 using Rhino.Mocks;
+using Wti.Calculation.Test.Piping.Stub;
 using Wti.Data;
 using Wti.Forms.NodePresenters;
 using Wti.Forms.Test.Helper;
@@ -273,7 +274,7 @@
         }
 
         [Test]
-        public void CanRemove_Always_ReturnTrue()
+        public void CanRemove_Always_ReturnFalse()
         {
             // Setup
             var mocks = new MockRepository();
@@ -287,27 +288,21 @@
             bool removalAllowed = nodePresenter.CanRemove(dataMock, nodeMock);
 
             // Assert
-            Assert.IsTrue(removalAllowed);
+            Assert.IsFalse(removalAllowed);
             mocks.VerifyAll(); // Expect no calls on arguments
         }
 
         [Test]
-        public void RemoveNodeData_ProjectWithPipingData_ReturnFalse()
+        public void RemoveNodeData_Always_ReturnFalse()
         {
             // Setup
-            var pipingData = new PipingData();
-
-            var project = new Project();
-            project.Items.Add(pipingData);
-
             var nodePresenter = new PipingOutputNodePresenter();
 
             // Call
-            bool removalSuccesful = nodePresenter.RemoveNodeData(project, pipingData);
+            bool removalSuccesful = nodePresenter.RemoveNodeData(null, null);
 
             // Assert
             Assert.IsFalse(removalSuccesful);
-            CollectionAssert.Contains(project.Items, pipingData);
         }
     }
 }
\ No newline at end of file
Index: test/Plugins/Wti/Wti.Forms.Test/PipingContextMenuStripTest.cs
===================================================================
diff -u -ra3b93c36c2051bd6112327bff0d836ae7883737d -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Forms.Test/PipingContextMenuStripTest.cs	(.../PipingContextMenuStripTest.cs)	(revision a3b93c36c2051bd6112327bff0d836ae7883737d)
+++ test/Plugins/Wti/Wti.Forms.Test/PipingContextMenuStripTest.cs	(.../PipingContextMenuStripTest.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -6,26 +6,43 @@
     public class PipingContextMenuStripTest
     {
         [Test]
-        public void Constructor_Always_OneMenuItemIsAdded()
+        public void Constructor_Always_ValidateAndCalculateItemsAreAdded()
         {
             var actual = new PipingContextMenuStrip(null);
-            Assert.AreEqual(1, actual.Items.Count);
+            Assert.AreEqual(2, actual.Items.Count);
             CollectionAssert.AllItemsAreNotNull(actual.Items);
         }
 
         [Test]
-        public void OnClick_Always_NoExceptions()
+        public void OnClick_CalculateItemAlways_NoExceptions()
         {
             var pipingContextMenu = new PipingContextMenuStrip(null);
+            pipingContextMenu.Items[1].PerformClick();
+        }
+
+        [Test]
+        public void OnClick_ValidateItemAlways_NoExceptions()
+        {
+            var pipingContextMenu = new PipingContextMenuStrip(null);
             pipingContextMenu.Items[0].PerformClick();
         }
 
         [Test]
-        public void OnClick_HandlerActionDefined_ActionIsExecuted()
+        public void OnClick_CalculateItemOnCalculateHandlerActionDefined_ActionIsExecuted()
         {
             var executed = false;
             var pipingContextMenu = new PipingContextMenuStrip(null);
             pipingContextMenu.OnCalculationClick += p => executed = true;
+            pipingContextMenu.Items[1].PerformClick();
+            Assert.IsTrue(executed);
+        }
+
+        [Test]
+        public void OnClick_ValidateItemOnValidateHandlerActionDefined_ActionIsExecuted()
+        {
+            var executed = false;
+            var pipingContextMenu = new PipingContextMenuStrip(null);
+            pipingContextMenu.OnValidationClick += p => executed = true;
             pipingContextMenu.Items[0].PerformClick();
             Assert.IsTrue(executed);
         }
Index: test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs
===================================================================
diff -u -r1689206627a4343d07fafcebb0a931b7a0e9e2d2 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs	(.../PipingCalculationServiceTest.cs)	(revision 1689206627a4343d07fafcebb0a931b7a0e9e2d2)
+++ test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs	(.../PipingCalculationServiceTest.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -1,58 +1,104 @@
 using NUnit.Framework;
-using Wti.Calculation.Piping;
+using Rhino.Mocks;
+using Wti.Calculation.Test.Piping.Stub;
 using Wti.Data;
 
 namespace Wti.Service.Test
 {
     public class PipingCalculationServiceTest
     {
-        private readonly PipingData validPipingData = new PipingData
+        private PipingData validPipingData;
+
+        [SetUp]
+        public void SetUp()
         {
-            AssessmentLevel = 1.0,
-            BeddingAngle = 1.0,
-            CriticalHeaveGradient = 1.0,
-            DampingFactorExit = 1.0,
-            DarcyPermeability = 1.0,
-            Diameter70 = 1.0,
-            ExitPointXCoordinate = 1.0,
-            Gravity = 1.0,
-            MeanDiameter70 = 1.0,
-            PiezometricHeadExit = 1.0,
-            PiezometricHeadPolder = 1.0,
-            PhreaticLevelExit = 2.0,
-            SandParticlesVolumicWeight = 1.0,
-            SeepageLength = 1.0,
-            SellmeijerModelFactor = 1.0,
-            SellmeijerReductionFactor = 1.0,
-            ThicknessAquiferLayer = 1.0,
-            ThicknessCoverageLayer = 1.0,
-            UpliftModelFactor = 1.0,
-            WaterKinematicViscosity = 1.0,
-            WaterVolumetricWeight = 1.0,
-            WhitesDragCoefficient = 1.0
-        };
+            validPipingData = new PipingData
+            {
+                AssessmentLevel = 1.0,
+                BeddingAngle = 1.0,
+                CriticalHeaveGradient = 1.0,
+                DampingFactorExit = 1.0,
+                DarcyPermeability = 1.0,
+                Diameter70 = 1.0,
+                ExitPointXCoordinate = 1.0,
+                Gravity = 1.0,
+                MeanDiameter70 = 1.0,
+                PiezometricHeadExit = 1.0,
+                PiezometricHeadPolder = 1.0,
+                PhreaticLevelExit = 2.0,
+                SandParticlesVolumicWeight = 1.0,
+                SeepageLength = 1.0,
+                SellmeijerModelFactor = 1.0,
+                SellmeijerReductionFactor = 1.0,
+                ThicknessAquiferLayer = 1.0,
+                ThicknessCoverageLayer = 1.0,
+                UpliftModelFactor = 1.0,
+                WaterKinematicViscosity = 1.0,
+                WaterVolumetricWeight = 1.0,
+                WhitesDragCoefficient = 1.0
+            };
+        }
 
         [Test]
-        public void Calculate_ValidPipingData_ShouldSetOutput()
+        public void PerfromValidatedCalculation_ValidPipingDataNoOutput_ShouldSetOutput()
         {
+            // Precondition
+            Assert.IsNull(validPipingData.Output);
+
             // Call
-            PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
 
             // Assert
+            Assert.AreEqual(PipingCalculationResult.Successful, result);
             Assert.NotNull(validPipingData.Output);
         }
 
         [Test]
-        public void Calculate_InValidPipingData_ReturnsErrorMessages()
+        public void PerfromValidatedCalculation_ValidPipingDataWithOutput_ShouldChangeOutput()
         {
             // Setup
-            var invalidPipingData = new PipingData();
+            var output = new TestPipingOutput();
+            validPipingData.Output = output;
 
             // Call
-            var results = PipingCalculationService.PerfromValidatedCalculation(invalidPipingData);
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+
+            // Assert
+            Assert.AreEqual(PipingCalculationResult.Successful, result);
+            Assert.AreNotSame(output, validPipingData.Output);
+        }
+
+        [Test]
+        public void PerfromValidatedCalculation_InValidPipingDataWithOutput_ReturnsFalseNoOutputChange()
+        {
+            // Setup
+            var output = new TestPipingOutput();
+            var invalidPipingData = new PipingData
+            {
+                Output = output
+            };
+
+            // Call
+            var result = PipingCalculationService.PerfromValidatedCalculation(invalidPipingData);
             
             // Assert
-            CollectionAssert.IsNotEmpty(results);
+            Assert.AreEqual(PipingCalculationResult.ValidationErrors, result);
+            Assert.AreSame(output, invalidPipingData.Output);
         }
+
+        [Test]
+        public void PerformValidatedCalculation_Diameter70AndAquiferPermeabilityZero_CalculationErrorOutputNull()
+        {
+            // Setup
+            validPipingData.Diameter70 = 0;
+            validPipingData.DarcyPermeability = 0;
+
+            // Call
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+
+            // Assert
+            Assert.AreEqual(PipingCalculationResult.CalculationErrors, result);
+            Assert.Null(validPipingData.Output);
+        }
     }
 }
\ No newline at end of file
Index: test/Plugins/Wti/Wti.Service.Test/Wti.Service.Test.csproj
===================================================================
diff -u -rbcf5bfda6fc2fca0b4229b9181df3d217fe1b33f -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Service.Test/Wti.Service.Test.csproj	(.../Wti.Service.Test.csproj)	(revision bcf5bfda6fc2fca0b4229b9181df3d217fe1b33f)
+++ test/Plugins/Wti/Wti.Service.Test/Wti.Service.Test.csproj	(.../Wti.Service.Test.csproj)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -34,6 +34,9 @@
     <Reference Include="nunit.framework">
       <HintPath>..\..\..\..\lib\nunit.framework.dll</HintPath>
     </Reference>
+    <Reference Include="Rhino.Mocks">
+      <HintPath>..\..\..\..\lib\Rhino.Mocks.dll</HintPath>
+    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
     <Reference Include="System.Windows.Forms" />
@@ -76,6 +79,10 @@
       <Project>{7cd038e1-e111-4969-aced-22c5bd2974e1}</Project>
       <Name>Wti.Forms</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\..\..\Wti.Calculation.TestUtil\Wti.Calculation.TestUtil.csproj">
+      <Project>{27E0A5C9-3ABF-426A-A3DA-7D0B83A218C8}</Project>
+      <Name>Wti.Calculation.TestUtil</Name>
+    </ProjectReference>
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.