diff --git a/BauSystem/BauSystem_Main/src/de/steamwar/bausystem/features/util/PistonCalculator.java b/BauSystem/BauSystem_Main/src/de/steamwar/bausystem/features/util/PistonCalculator.java
index bbb8ac3b..9944c549 100644
--- a/BauSystem/BauSystem_Main/src/de/steamwar/bausystem/features/util/PistonCalculator.java
+++ b/BauSystem/BauSystem_Main/src/de/steamwar/bausystem/features/util/PistonCalculator.java
@@ -91,7 +91,7 @@ public class PistonCalculator implements Listener {
     public void onBlockPistonExtend(BlockPistonExtendEvent event) {
         Bukkit.getScheduler().runTaskLater(BauSystem.getInstance(), () -> {
             pistOrders.values().forEach(PistOrder::calculate);
-        }, 1);
+        }, 3);
     }
 
     @EventHandler
@@ -146,7 +146,7 @@ public class PistonCalculator implements Listener {
         private boolean pulling = false;
         private List<Location> movedBlocks = new ArrayList<>();
         private List<Location> brokenBlocks = new ArrayList<>();
-        private List<Location> immovableBlocks = new ArrayList<>();
+        private Set<Location> immovableBlocks = new HashSet<>();
 
         public void calculate() {
             movedBlocks.clear();
@@ -173,7 +173,6 @@ public class PistonCalculator implements Listener {
 
             Collections.reverse(movedBlocks);
             Collections.reverse(brokenBlocks);
-            Collections.reverse(immovableBlocks);
 
             visualize();
         }
@@ -208,6 +207,7 @@ public class PistonCalculator implements Listener {
 
             movedBlocks.remove(origin.getLocation());
             if (facing != direction) movedBlocks.remove(origin.getRelative(facing, 1).getLocation());
+            if (pulling) immovableBlocks.remove(origin.getRelative(facing).getLocation());
         }
 
         private void calcDirection(Block origin, Block blockOrigin, Block calcOrigin, Block ignore, BlockFace facing, BlockFace direction, List<Block> toCalc) {
@@ -215,7 +215,9 @@ public class PistonCalculator implements Listener {
                 Block block = calcOrigin.getRelative(direction, i);
                 if (block.equals(ignore)) return;
                 if (block.getPistonMoveReaction() == PistonMoveReaction.BREAK) {
-                    brokenBlocks.add(block.getLocation());
+                    if (!brokenBlocks.contains(block.getLocation())) {
+                        brokenBlocks.add(block.getLocation());
+                    }
                     return;
                 }
                 if (isImmovable(block)) {
@@ -302,6 +304,9 @@ public class PistonCalculator implements Listener {
     }
 
     private boolean isImmovable(Block block) {
+        if (block.isEmpty() || block.isLiquid()) {
+            return false;
+        }
         BlockData blockData = block.getBlockData();
         if (blockData instanceof Piston) {
             return ((Piston) blockData).isExtended();