Possible causes, valid for the following automatic domestic water heaters:
4000/5E - item no. 1758
5000/5E - item no. 1759
6000/6E - item no. 1760
smart automatic water heater 5000/5 Art. no. 19080
There is no spring in the non-return valve of these automatic domestic water valves. The valve closes automatically when no more water is drawn off. The non-return valve can remain open if it is dirty. When removing and reinstalling, check whether the non-return valve closes automatically. The cone of the non-return valve must fall slightly to the valve seat of the pump. The valve can also become leaky due to contamination such as sand or limescale. A defective or missing sealing ring (O-ring) may also be responsible for the leakage.
Instructions for removing the built-in non-return valve.
1. switch switch (11) to O.
2. unplug the mains plug.
3 If necessary, close all valves on the suction side.
4. close all tapping points again to prevent the connected pipes from running empty via the automatic domestic water system.
5 Unscrew the cover (14) of the non-return valve using a suitable tool.
6. remove the valve body (15) and clean under running water.
7. refit the non-return valve in reverse order
8. restart the automatic domestic water system.