Index: Ringtoets/Piping/src/Ringtoets.Piping.Forms/Extensions/PipingInputExtensions.cs
===================================================================
diff -u -r2a7be595bf1251849a3c5f3be000f0e40f8fa874 -r98a291d574281a04a9e0a243d8a4429a1ffb9379
--- Ringtoets/Piping/src/Ringtoets.Piping.Forms/Extensions/PipingInputExtensions.cs	(.../PipingInputExtensions.cs)	(revision 2a7be595bf1251849a3c5f3be000f0e40f8fa874)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Forms/Extensions/PipingInputExtensions.cs	(.../PipingInputExtensions.cs)	(revision 98a291d574281a04a9e0a243d8a4429a1ffb9379)
@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using Ringtoets.Piping.Data;
+using Ringtoets.Piping.Forms.Properties;
 
 namespace Ringtoets.Piping.Forms.Extensions
 {
@@ -57,5 +58,43 @@
             input.SeepageLength.Mean = mean;
             input.SeepageLength.StandardDeviation = mean * PipingInput.SeepageLengthStandardDeviationFraction;
         }
+
+        /// <summary>
+        /// Sets the L-coordinate of the entry point.
+        /// </summary>
+        /// <param name="input">The <see cref="PipingInput"/> to update the entry point for.</param>
+        /// <param name="entryPointL">The L-coordinate of the entry point to set.</param>
+        public static void SetEntryPointL(this PipingInput input, double entryPointL)
+        {
+            try
+            {
+                input.SetSeepageLengthMean(input.ExitPointL - entryPointL);
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                var message = string.Format(Resources.PipingInputContextProperties_EntryPointL_Value_0_results_in_invalid_seepage_length, entryPointL);
+                throw new ArgumentException(message);
+            }
+        }
+
+        /// <summary>
+        /// Sets the L-coordinate of the exit point.
+        /// </summary>
+        /// <param name="input">The <see cref="PipingInput"/> to update the entry point for.</param>
+        /// <param name="exitPointL">The L-coordinate of the entry point to set.</param>
+        public static void SetExitPointL(this PipingInput input, double exitPointL)
+        {
+            var exitPointLChange = exitPointL - input.ExitPointL;
+            try
+            {
+                input.SetSeepageLengthMean(input.SeepageLength.Mean + exitPointLChange);
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                var message = string.Format(Resources.PipingInputContextProperties_ExitPointL_Value_0_results_in_invalid_seepage_length, exitPointL);
+                throw new ArgumentException(message);
+            }
+            input.ExitPointL = exitPointL;
+        }
     }
 }
\ No newline at end of file
Index: Ringtoets/Piping/src/Ringtoets.Piping.Forms/PropertyClasses/PipingInputContextProperties.cs
===================================================================
diff -u -r2a7be595bf1251849a3c5f3be000f0e40f8fa874 -r98a291d574281a04a9e0a243d8a4429a1ffb9379
--- Ringtoets/Piping/src/Ringtoets.Piping.Forms/PropertyClasses/PipingInputContextProperties.cs	(.../PipingInputContextProperties.cs)	(revision 2a7be595bf1251849a3c5f3be000f0e40f8fa874)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Forms/PropertyClasses/PipingInputContextProperties.cs	(.../PipingInputContextProperties.cs)	(revision 98a291d574281a04a9e0a243d8a4429a1ffb9379)
@@ -362,16 +362,7 @@
             }
             set
             {
-                try
-                {
-                    data.WrappedData.SetSeepageLengthMean(data.WrappedData.ExitPointL - value);
-                }
-                catch (ArgumentOutOfRangeException)
-                {
-                    var message = string.Format(Resources.PipingInputContextProperties_EntryPointL_Value_0_results_in_invalid_seepage_length, value);
-                    throw new ArgumentException(message);
-                }
-
+                data.WrappedData.SetEntryPointL(value);
                 data.WrappedData.NotifyObservers();
             }
         }
@@ -387,18 +378,7 @@
             }
             set
             {
-                try
-                {
-                    var exitPointLChange = value - data.WrappedData.ExitPointL;
-                    data.WrappedData.SetSeepageLengthMean(data.WrappedData.SeepageLength.Mean + exitPointLChange);
-                }
-                catch (ArgumentOutOfRangeException)
-                {
-                    var message = string.Format(Resources.PipingInputContextProperties_ExitPointL_Value_0_results_in_invalid_seepage_length, value);
-                    throw new ArgumentException(message);
-                }
-
-                data.WrappedData.ExitPointL = value;
+                data.WrappedData.SetExitPointL(value);
                 data.WrappedData.NotifyObservers();
             }
         }
Index: Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Extensions/PipingInputExtensionsTest.cs
===================================================================
diff -u -r2a7be595bf1251849a3c5f3be000f0e40f8fa874 -r98a291d574281a04a9e0a243d8a4429a1ffb9379
--- Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Extensions/PipingInputExtensionsTest.cs	(.../PipingInputExtensionsTest.cs)	(revision 2a7be595bf1251849a3c5f3be000f0e40f8fa874)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/Extensions/PipingInputExtensionsTest.cs	(.../PipingInputExtensionsTest.cs)	(revision 98a291d574281a04a9e0a243d8a4429a1ffb9379)
@@ -1,7 +1,10 @@
-using Core.Common.Base.Geometry;
+using System;
+using Core.Common.Base.Geometry;
+using Core.Common.TestUtil;
 using NUnit.Framework;
 using Ringtoets.Piping.Data;
 using Ringtoets.Piping.Forms.Extensions;
+using Ringtoets.Piping.Forms.Properties;
 
 namespace Ringtoets.Piping.Forms.Test.Extensions
 {
@@ -115,5 +118,153 @@
             Assert.AreEqual(0.2, inputParameters.SeepageLength.StandardDeviation);
             Assert.AreEqual(thirdPointX - firstPointX, inputParameters.ExitPointL);
         }
+
+        [Test]
+        [TestCase(2, 0, 2)]
+        [TestCase(2, -2, 4)]
+        [TestCase(0.5, -3.5, 4)]
+        [TestCase(1e-6, -(4 - 1e-6), 4)]
+        [TestCase(3 + 1e-6, 3, 1e-6)]
+        [TestCase(0.5, 0.5 - 1e-6, 1e-6)]
+        public void SetEntryPointL_ExitPointAndSeepageLengthSet_UpdatesSeepageLength(double exitPoint, double entryPoint, double seepageLength)
+        {
+            // Setup
+            var random = new Random(22);
+
+            var surfaceLine = ValidSurfaceLine(0.0, 4.0);
+            var soilProfile = new PipingSoilProfile(String.Empty, random.NextDouble(), new[]
+            {
+                new PipingSoilLayer(random.NextDouble())
+                {
+                    IsAquifer = true
+                }
+            });
+            var input = new PipingInput
+            {
+                SurfaceLine = surfaceLine,
+                SoilProfile = soilProfile,
+                ExitPointL = exitPoint
+            };
+
+            input.SetEntryPointL(entryPoint);
+
+            // Call & Assert
+            Assert.AreEqual(exitPoint, input.ExitPointL);
+            Assert.AreEqual(seepageLength, input.SeepageLength.Mean, 1e-6);
+        }
+
+        [Test]
+        [TestCase(2, 2, 4)]
+        [TestCase(4, 2, 6)]
+        [TestCase(4, 0.5, 4.5)]
+        [TestCase(1e-6, 4, 4 + 1e-6)]
+        [TestCase(3, -1e-6, 3 - 1e-6)]
+        [TestCase(0.5, 1e-6, 0.5 + 1e-6)]
+        public void SetExitPointL_ExitPointAndSeepageLengthSet_UpdatesSeepageLength(double seepageLength, double exitPoint, double newSeepageLength)
+        {
+            // Setup
+            var random = new Random(22);
+
+            var surfaceLine = ValidSurfaceLine(0.0, 4.0);
+            var soilProfile = new PipingSoilProfile(String.Empty, random.NextDouble(), new[]
+            {
+                new PipingSoilLayer(random.NextDouble())
+                {
+                    IsAquifer = true
+                }
+            });
+            var input = new PipingInput
+            {
+                SurfaceLine = surfaceLine,
+                SoilProfile = soilProfile,
+                SeepageLength =
+                {
+                    Mean = seepageLength
+                }
+            };
+
+            input.SetExitPointL(exitPoint);
+
+            // Call & Assert
+            Assert.AreEqual(exitPoint, input.ExitPointL);
+            Assert.AreEqual(newSeepageLength, input.SeepageLength.Mean);
+        }
+
+        [Test]
+        public void SetEntryPointL_SetResultInInvalidSeePage_ThrowsArgumentException()
+        {
+            // Setup
+            var random = new Random(22);
+
+            var surfaceLine = ValidSurfaceLine(0.0, 4.0);
+            var soilProfile = new PipingSoilProfile(String.Empty, random.NextDouble(), new[]
+            {
+                new PipingSoilLayer(random.NextDouble())
+                {
+                    IsAquifer = true
+                }
+            });
+
+            var l = 2.0;
+            var input = new PipingInput
+            {
+                SurfaceLine = surfaceLine,
+                SoilProfile = soilProfile,
+                ExitPointL = l
+            };
+
+
+            // Call
+            TestDelegate test = () => input.SetEntryPointL(l);
+
+            // Assert
+            var message = string.Format(Resources.PipingInputContextProperties_EntryPointL_Value_0_results_in_invalid_seepage_length, l);
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentException>(test, message);
+        }
+
+        [Test]
+        public void SetExitPointL_SetResultInInvalidSeePage_ThrowsArgumentException()
+        {
+            // Setup
+            var random = new Random(22);
+
+            var surfaceLine = ValidSurfaceLine(0.0, 4.0);
+            var soilProfile = new PipingSoilProfile(String.Empty, random.NextDouble(), new[]
+            {
+                new PipingSoilLayer(random.NextDouble())
+                {
+                    IsAquifer = true
+                }
+            });
+            var l = -2.0;
+            var input = new PipingInput
+            {
+                SurfaceLine = surfaceLine,
+                SoilProfile = soilProfile,
+                SeepageLength =
+                {
+                    Mean = -l
+                }
+            };
+
+
+            // Call
+            TestDelegate test = () => input.SetExitPointL(l);
+
+            // Assert
+            var message = string.Format(Resources.PipingInputContextProperties_ExitPointL_Value_0_results_in_invalid_seepage_length, l);
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentException>(test, message);
+        }
+
+        private static RingtoetsPipingSurfaceLine ValidSurfaceLine(double xMin, double xMax)
+        {
+            var surfaceLine = new RingtoetsPipingSurfaceLine();
+            surfaceLine.SetGeometry(new[]
+            {
+                new Point3D(xMin, 0.0, 0.0),
+                new Point3D(xMax, 0.0, 1.0)
+            });
+            return surfaceLine;
+        }
     }
 }
\ No newline at end of file