diff --git a/PamhagenSysCtrl/Helpers/PamhagenGraph.cs b/PamhagenSysCtrl/Helpers/PamhagenGraph.cs
index 7724ae7..189a633 100644
--- a/PamhagenSysCtrl/Helpers/PamhagenGraph.cs
+++ b/PamhagenSysCtrl/Helpers/PamhagenGraph.cs
@@ -28,8 +28,8 @@ namespace PamhagenSysCtrl.Helpers {
             double t8X = t7X + 80;
             double t9X = t8X + 80;
 
-            MW1 = new Trough("MW1", mw1X, mpY - 40, () => App.Plant?.FillLevelA1 != FillState.Empty);
-            MW2 = new Trough("MW2", mw2X, mpY - 40, () => App.Plant?.FillLevelA1 != FillState.Empty);
+            MW1 = new Trough("MW1", mw1X, mpY - 70, () => App.Plant?.FillLevelA1 != FillState.Empty);
+            MW2 = new Trough("MW2", mw2X, mpY - 70, () => App.Plant?.FillLevelA1 != FillState.Empty);
             var mp1 = new Pump("MP1", mw1X, mpY);
             var mp2 = new Pump("MP2", mw2X, mpY);
             var x1 = new PipeJoin(mw1X, mpY + 40);
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Graph.cs b/PamhagenSysCtrl/Helpers/Pipeline/Graph.cs
index 5979807..fb0be24 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Graph.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Graph.cs
@@ -62,7 +62,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             foreach (var o in start.Outputs) {
                 if (o.End == end) {
                     return new(start, [(o, o.End)]);
-                } else if (!valid(o.End)) {
+                } else if (!valid(o.End) || (!o.IsTwoWay && o.End == start) || (o.IsTwoWay && o.End == start)) {
                     continue;
                 }
 
@@ -91,13 +91,13 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             }
         }
 
-        public ISet<INode> Update(double x, double y) {
+        public ISet<INode> Update(double x, double y, bool down) {
             HashSet<INode> hover = new();
             foreach (var e in Edges) {
-                e.Update(x, y);
+                e.Update();
             }
             foreach (var n in Nodes) {
-                if (n.Update(x, y)) {
+                if (n.Update(x, y, down)) {
                     hover.Add(n);
                 }
             }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/IEdge.cs b/PamhagenSysCtrl/Helpers/Pipeline/IEdge.cs
index 4211e6d..538cf70 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/IEdge.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/IEdge.cs
@@ -11,7 +11,6 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
         public Brush? Highlight { get; set; }
 
         public void Draw(Canvas canvas);
-        public bool Update(double x, double y);
-
+        public void Update();
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/INode.cs b/PamhagenSysCtrl/Helpers/Pipeline/INode.cs
index 85dc744..3de60f3 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/INode.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/INode.cs
@@ -10,7 +10,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
         public ISet<IEdge> Outputs { get; }
 
         public void Draw(Canvas canvas);
-        public bool Update(double x, double y);
+        public bool Update(double x, double y, bool down);
 
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/ISource.cs b/PamhagenSysCtrl/Helpers/Pipeline/ISource.cs
index 5a9da86..2913d6c 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/ISource.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/ISource.cs
@@ -2,5 +2,6 @@
     public interface ISource : INode {
         public double BottomY { get; }
         public bool IsFilled { get; }
+        public bool IsSelected { get; set; }
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Inlet.cs b/PamhagenSysCtrl/Helpers/Pipeline/Inlet.cs
index 16a8e52..da2561a 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Inlet.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Inlet.cs
@@ -76,10 +76,9 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_inner2);
         }
 
-        public bool Update(double x, double y) {
+        public void Update() {
             _inner1?.Stroke = Highlight ?? Brushes.DarkGray;
             _inner2?.Stroke = Highlight ?? Brushes.DarkGray;
-            return false;
         }
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Outlet.cs b/PamhagenSysCtrl/Helpers/Pipeline/Outlet.cs
index 24fe67c..e51db1e 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Outlet.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Outlet.cs
@@ -86,11 +86,10 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_inner2);
         }
 
-        public bool Update(double x, double y) {
+        public void Update() {
             _inner1?.Stroke = Highlight ?? Brushes.DarkGray;
             _inner2?.Stroke = Highlight ?? Brushes.DarkGray;
             _hopper?.Fill = Highlight ?? Brushes.DarkGray;
-            return false;
         }
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Pipe.cs b/PamhagenSysCtrl/Helpers/Pipeline/Pipe.cs
index b4518bf..c10f022 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Pipe.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Pipe.cs
@@ -65,10 +65,9 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_inner2);
         }
 
-        public bool Update(double x, double y) {
+        public void Update() {
             _inner1?.Stroke = Highlight ?? Brushes.DarkGray;
             _inner2?.Stroke = Highlight ?? Brushes.DarkGray;
-            return false;
         }
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/PipeJoin.cs b/PamhagenSysCtrl/Helpers/Pipeline/PipeJoin.cs
index cd50c58..ba455e4 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/PipeJoin.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/PipeJoin.cs
@@ -81,7 +81,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_rect);
         }
 
-        public bool Update(double x, double y) {
+        public bool Update(double x, double y, bool down) {
             var hover = Math.Abs(x - CenterX) <= SIZE / 2 && Math.Abs(y - CenterY) <= SIZE / 2;
             _rect?.Stroke = hover ? Brushes.Black : Brushes.Black;
             return hover;
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Press.cs b/PamhagenSysCtrl/Helpers/Pipeline/Press.cs
index 7b7dc24..54af9d4 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Press.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Press.cs
@@ -59,7 +59,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_text);
         }
 
-        public bool Update(double x, double y) {
+        public bool Update(double x, double y, bool down) {
             var hover = Math.Sqrt(Math.Pow(CenterX - x, 2) + Math.Pow(CenterY - y, 2)) <= DIAMETER / 2;
             _circle?.Fill = hover ? Brushes.LightGray : Brushes.WhiteSmoke;
             return hover;
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Pump.cs b/PamhagenSysCtrl/Helpers/Pipeline/Pump.cs
index 8c41a9d..e3a3570 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Pump.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Pump.cs
@@ -58,7 +58,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_text);
         }
 
-        public bool Update(double x, double y) {
+        public bool Update(double x, double y, bool down) {
             var hover = Math.Sqrt(Math.Pow(CenterX - x, 2) + Math.Pow(CenterY - y, 2)) <= DIAMETER / 2;
             _circle?.Fill = hover ? Brushes.LightGray : Brushes.WhiteSmoke;
             return hover;
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Tank.cs b/PamhagenSysCtrl/Helpers/Pipeline/Tank.cs
index 740b990..d4b6eea 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Tank.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Tank.cs
@@ -16,6 +16,7 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
         public string Label { get; set; }
         public bool IsFull => CallbackIsFull();
         public bool IsFilled => CallbackIsFilled();
+        public bool IsSelected { get; set; }
 
         public ISet<IEdge> Inputs { get; init; }
         public ISet<IEdge> Outputs { get; init; }
@@ -62,9 +63,9 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_text);
         }
 
-        public bool Update(double x, double y) {
+        public bool Update(double x, double y, bool down) {
             var hover = Math.Abs(x - CenterX) <= WIDTH / 2 && Math.Abs(y - CenterY) <= HEIGHT / 2;
-            _rect?.Fill = hover ? Brushes.LightGray : Brushes.WhiteSmoke;
+            _rect?.Fill = IsSelected ? Brushes.LightGray : hover ? Brushes.LightGray : Brushes.WhiteSmoke;
             return hover;
         }
     }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Trough.cs b/PamhagenSysCtrl/Helpers/Pipeline/Trough.cs
index 9f7dde0..e0a9b0b 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Trough.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Trough.cs
@@ -1,18 +1,28 @@
-using System.Windows.Controls;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media;
+using System.Windows.Shapes;
 
 namespace PamhagenSysCtrl.Helpers.Pipeline {
     public class Trough : INode, ISource {
 
+        public const double WIDTH = 100;
+        public const double HEIGHT = 60;
+
         public double CenterX { get; set; }
         public double CenterY { get; set; }
-        public double BottomY => CenterY;
+        public double BottomY => CenterY + HEIGHT / 2;
         public string Label { get; set; }
         public bool IsFilled => CallbackIsFilled();
+        public bool IsSelected { get; set; }
         public ISet<IEdge> Inputs { get; init; }
         public ISet<IEdge> Outputs { get; init; }
 
         protected Func<bool> CallbackIsFilled;
 
+        private Shape? _rect;
+        private TextBlock? _text;
+
         public Trough(string label, double x, double y, Func<bool> cbFilled) {
             CenterX = x;
             CenterY = y;
@@ -23,11 +33,32 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
         }
 
         public void Draw(Canvas canvas) {
-            
+            _rect = new Rectangle() {
+                Width = WIDTH,
+                Height = HEIGHT,
+                Stroke = Brushes.Black,
+                StrokeThickness = 2,
+                Fill = Brushes.WhiteSmoke,
+            };
+            _text = new() {
+                Text = Label,
+                FontSize = 12,
+                Width = WIDTH,
+                TextAlignment = TextAlignment.Center,
+                VerticalAlignment = VerticalAlignment.Center,
+            };
+            _rect.SetValue(Canvas.LeftProperty, CenterX - WIDTH / 2);
+            _rect.SetValue(Canvas.TopProperty, CenterY - HEIGHT / 2);
+            _text.SetValue(Canvas.LeftProperty, CenterX - WIDTH / 2);
+            _text.SetValue(Canvas.TopProperty, CenterY - 8);
+            canvas.Children.Add(_rect);
+            canvas.Children.Add(_text);
         }
 
-        public bool Update(double x, double y) {
-            return false;
+        public bool Update(double x, double y, bool down) {
+            var hover = Math.Abs(x - CenterX) <= WIDTH / 2 && Math.Abs(y - CenterY) <= HEIGHT / 2;
+            _rect?.Fill = IsSelected ? Brushes.LightGray : hover ? Brushes.LightGray : Brushes.WhiteSmoke;
+            return hover;
         }
     }
 }
diff --git a/PamhagenSysCtrl/Helpers/Pipeline/Valve.cs b/PamhagenSysCtrl/Helpers/Pipeline/Valve.cs
index 96f5217..bacf8de 100644
--- a/PamhagenSysCtrl/Helpers/Pipeline/Valve.cs
+++ b/PamhagenSysCtrl/Helpers/Pipeline/Valve.cs
@@ -11,7 +11,9 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
         public double CenterX { get; set; }
         public double CenterY { get; set; }
         public string Label { get; set; }
+        public Brush? Highlight { get; set; }
 
+        public bool IsLocked { get; set; }
         public bool IsOpen => CallbackIsOpen();
         public bool WantOpen => CallbackWantOpen();
         public ISet<IEdge> Inputs { get; init; }
@@ -57,9 +59,9 @@ namespace PamhagenSysCtrl.Helpers.Pipeline {
             canvas.Children.Add(_text);
         }
 
-        public bool Update(double x, double y) {
+        public bool Update(double x, double y, bool down) {
             var hover = Math.Sqrt(Math.Pow(CenterX - x, 2) + Math.Pow(CenterY - y, 2)) <= DIAMETER / 2;
-            _circle?.Fill = hover ? Brushes.LightGray : Brushes.DarkGray;
+            _circle?.Fill = IsLocked ? Brushes.Red : Highlight ?? (hover ? Brushes.LightGray : Brushes.DarkGray);
             return hover;
         }
     }
diff --git a/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml b/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml
index 00fb485..90ddc3f 100644
--- a/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml
+++ b/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml
@@ -5,7 +5,7 @@
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         xmlns:local="clr-namespace:PamhagenSysCtrl.Windows"
         Title="Schema - Anlagensteuerung Pamhagen" Height="800" Width="1600">
-    <Grid MouseMove="SchemeCanvas_MouseMove">
+    <Grid MouseMove="SchemeCanvas_MouseMove" MouseLeftButtonDown="SchemeCanvas_MouseLeftButtonDown" MouseLeftButtonUp="SchemeCanvas_MouseLeftButtonUp">
         <Canvas x:Name="SchemeCanvas">
         </Canvas>
     </Grid>
diff --git a/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml.cs b/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml.cs
index ef8a22e..6c8e021 100644
--- a/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml.cs
+++ b/PamhagenSysCtrl/Windows/PlantSchemeWindow.xaml.cs
@@ -8,6 +8,10 @@ namespace PamhagenSysCtrl.Windows {
     public partial class PlantSchemeWindow : Window {
 
         private readonly PamhagenGraph Graph;
+        private readonly List<Path> Paths = [];
+
+        private ISource? _lastSource;
+        private ISet<INode>? _lastSelected;
 
         public PlantSchemeWindow() {
             InitializeComponent();
@@ -18,18 +22,83 @@ namespace PamhagenSysCtrl.Windows {
 
         private void SchemeCanvas_MouseMove(object sender, MouseEventArgs evt) {
             var p = evt.GetPosition(SchemeCanvas);
+            UpdateScheme(evt.GetPosition(SchemeCanvas), evt.LeftButton == MouseButtonState.Pressed);
+        }
+
+        private void SchemeCanvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs evt) {
+            var p = evt.GetPosition(SchemeCanvas);
+            _lastSelected = UpdateScheme(evt.GetPosition(SchemeCanvas), evt.LeftButton == MouseButtonState.Pressed);
+        }
+
+        private void SchemeCanvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs evt) {
+            var p = evt.GetPosition(SchemeCanvas);
+            var curSelected = UpdateScheme(evt.GetPosition(SchemeCanvas), evt.LeftButton == MouseButtonState.Pressed);
+            var clicked = curSelected.Intersect(_lastSelected ?? new HashSet<INode>()).ToList();
+            _lastSource?.IsSelected = false;
+            if (clicked.Count == 0) {
+                _lastSource = null;
+            }
+            foreach (var c in clicked) {
+                if (_lastSource != null && c is ISink sink) {
+                    var path = Graph.GetPath(_lastSource, sink, (n) => n is not ISink && (n is not Valve v || !v.IsLocked));
+                    if (path != null) {
+                        Paths.Add(path.Value);
+                        _lastSource = null;
+                    }
+                } else if (c is ISource source) {
+                    _lastSource = source;
+                    _lastSource.IsSelected = true;
+                } else {
+                    _lastSource = null;
+                }
+            }
+            UpdateScheme(evt.GetPosition(SchemeCanvas), evt.LeftButton == MouseButtonState.Pressed);
+        }
+
+        private ISet<INode> UpdateScheme(Point pos, bool down) {
             foreach (var e in Graph.Edges) {
                 e.Highlight = null;
             }
-            var hover = Graph.Update(p.X, p.Y);
-            if (hover.Count > 0) {
-                var path = Graph.GetPath(Graph.MW1, hover.First(), (n) => n is not ISink);
+            foreach (var p in Paths) {
+                var c = Brushes.Green;
+                foreach (var (edge, node) in p.Hops) {
+                    edge.Highlight = Brushes.Green;
+                    if (node is Pump) c = Brushes.Orange;
+                    ColorSubgraph(node, c, (v) => v.IsLocked = true);
+                }
+            }
+            var hover = Graph.Update(pos.X, pos.Y, down);
+            if (_lastSource != null && hover.Count > 0) {
+                var path = Graph.GetPath(_lastSource, hover.First(), (n) => n is not ISink && (n is not Valve v || !v.IsLocked));
                 if (path != null) {
+                    var c = Brushes.Green;
                     foreach (var (edge, node) in path.Value.Hops) {
                         edge.Highlight = Brushes.Green;
+                        if (node is Pump) c = Brushes.Orange;
+                        ColorSubgraph(node, c);
                     }
                 }
-                Graph.Update(p.X, p.Y);
+                Graph.Update(pos.X, pos.Y, down);
+            }
+            return hover;
+        }
+
+        private void ColorSubgraph(INode start, Brush color, Action<Valve>? valveAction = null) {
+            if (start is Valve v) {
+                valveAction?.Invoke(v);
+                return;
+            } else if (start is ISink || start is Pump) {
+                return;
+            }
+            foreach (var edge in start.Inputs) {
+                if (edge.Highlight != null) continue;
+                edge.Highlight = color;
+                ColorSubgraph(edge.Start, color, valveAction);
+            }
+            foreach (var edge in start.Outputs) {
+                if (edge.Highlight != null) continue;
+                edge.Highlight = color;
+                ColorSubgraph(edge.End, color, valveAction);
             }
         }