Vaillant water heater MAG125/TAN B11

[CalicoJack]

We have one of these which is used to provide hot water for washing etc. It is old (I think that Noah may have thrown it out), but has worked well until now. It currently thinks that the water is flowing when its turned on; sadly the taps are off! This is dangerous as the water just gets hotter and hotter. I guess that somewhere in it is a pressure/flow switch which has stuck open. My only thought on how to deal with this is to pump something like diluted vinegar into it so as to descale it. We are at Chatham and so have quite a build up of scale in the kettle. I have tried Vaillant but all I got was a 50p a minute help line, which after 8 mins had not been answered.

Any thoughts on the best way forward?

 

[Kurrawong_Kid]

Can you e-mail their helpline? Is there a website? Hope this reply is not too patronising!

 

[wells01]

I had one of these. There is a rubber diaphragm in the main valve which hardens over time. I made a new one out of inner tube and it worked for another 5 years.

 

[Marsupial]

Vaillant are (were) in Chatham in another life I dealt with them. The MAG125 is the best of its type, the good news is they stand a lot of stripping and rebuilding. As you water in kent the problem is almost certainly scale build up. If it was mine I would take it off the boat, strip it down and use a hot water system descaler on the heat exchanger and the pressure valve. If you dont want to do it yourself take it off and get a heating engineer to look at it.

Those things are bullet proof - worth the effort of overhauling.

edit - Just checked, they are still where I left them in 1989!!!

Vaillant Ltd.
Vaillant House
Trident Close
Medway City Estate
Rochester
Kent ME2 4EZ

 

[BobA]

www.uk-plumbing.com/vaillant-spares-vaillant-diaphragms-c-938_852_1244.html - 46k -

Spares here