Does your 5 liter Bonamat tank leak from the tap? Most often the reason is the seat cup acting as the faucet's shut-off. It is easy to replace yourself: when the tank is empty, turn the tap open counterclockwise, grasp the silicone cup and pull it out little by little. Press the new seat cup into place on the tap and screw the tap back onto the tank. Test waterproofness with cold water, for example.