Main Combi HE Dripping Water

I received a call from a customer because they had water dripping slowly from the underneath of their Main Combi HE. Knowing these boilers quite well I had a goood idea of what the issue might be before I got there. When I got there I could see that the water was dripping from the left-hand side close to the front. I removed the front casing and dropped the controls casing down to reveal the inside of the boiler. Instantly I could see that the water was leaking from the differential pressure switch on the front of the diverter valve which is a common problem.

The diverter valves and differential pressure switches can also be found on other boilers (Baxi Combi 80, Baxi Combi 105, Potterton Performa and Alpha 240/280) and it is not uncommon for them to leak. The leak usually comes from where the pin exits the hex nut behind the micro-switch and worsens when the hot tap is run. I had an Interpart diapragm kit and so dis-assembled the differential pressure switch. Whenever I strip one of these down I always clean the pin with a bit of wire wool as there always appears to be some scale build up on the pin which could damage the seal on the new hex nut.

I reassembled the boiler and turned the water back on and tested that the pin was moving as it should be without leaking and that the boiler was behaving as it should be.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.