Hopper won't acsept items brought over it by a water convayer.

Items brought to the hopper should fall down into it.

Instead they get caught on the lip edge of that block.

1. Creat a water trough 8 blocs long with a water sorce block at one end.
2. Place the hopper at the other end 9 blocks away and one block down.
Place items into the water.
3. They will not go down.