diff --git a/src/main/java/de/ellpeck/prettypipes/pipe/PipeBlock.java b/src/main/java/de/ellpeck/prettypipes/pipe/PipeBlock.java
index c82e621..75c04b0 100644
--- a/src/main/java/de/ellpeck/prettypipes/pipe/PipeBlock.java
+++ b/src/main/java/de/ellpeck/prettypipes/pipe/PipeBlock.java
@@ -227,6 +227,19 @@ public class PipeBlock extends ContainerBlock implements IPipeConnectable {
         }
     }
 
+    @Override
+    public boolean hasComparatorInputOverride(BlockState state) {
+        return true;
+    }
+
+    @Override
+    public int getComparatorInputOverride(BlockState blockState, World worldIn, BlockPos pos) {
+        PipeTileEntity pipe = Utility.getTileEntity(PipeTileEntity.class, worldIn, pos);
+        if (pipe == null)
+            return 0;
+        return Math.min(15, pipe.getItems().size());
+    }
+
     @Nullable
     @Override
     public TileEntity createNewTileEntity(IBlockReader worldIn) {
diff --git a/src/main/java/de/ellpeck/prettypipes/pipe/PipeTileEntity.java b/src/main/java/de/ellpeck/prettypipes/pipe/PipeTileEntity.java
index a451e7b..9228422 100644
--- a/src/main/java/de/ellpeck/prettypipes/pipe/PipeTileEntity.java
+++ b/src/main/java/de/ellpeck/prettypipes/pipe/PipeTileEntity.java
@@ -54,6 +54,7 @@ public class PipeTileEntity extends TileEntity implements INamedContainerProvide
         }
     };
     private List<PipeItem> items;
+    private int lastItemAmount;
     private int priority;
 
     public PipeTileEntity() {
@@ -115,6 +116,10 @@ public class PipeTileEntity extends TileEntity implements INamedContainerProvide
         List<PipeItem> items = this.getItems();
         for (int i = items.size() - 1; i >= 0; i--)
             items.get(i).updateInPipe(this);
+        if (items.size() != this.lastItemAmount) {
+            this.lastItemAmount = items.size();
+            this.world.updateComparatorOutputLevel(this.pos, this.getBlockState().getBlock());
+        }
         profiler.endSection();
     }