Combi Boiler diverter valve hell.

[was8v]

Well seeing as this seems to be the place to post DIY issues, here goes:

Combi boiler hot water hell:

1) Hot water stops working,I work out its the diverter valve pin not pushing the switch
2) remove diaphragm and its in pieces, replace with cheapo universal fit item
3) all is fine for a few months
4) boiler fires up with hot water but doesn't switch off when tap closed
5) diverter valve not returning - pin is sticking up keeping switch on. New diaphragm is split.
6) Buy genuine diaphragm cursing cheapo parts and fit
7) Now the problem is the hot tap needs to be on FULL before the pin will move enough to flick the switch. Turning the tap on a little or half way yields no hot water.

Now this would be OK if it were not for the mira shower - when on full mega hot water comes through. Turn the shower down a little and water pressure comes through the cold circuit dropping the pressure on the hot circuit and hence cutting the boiler leading to a cold shower.

I think the spring on the new diaphragm may be too hard. Has anyone heard of this?


Next step would be to chuck the whole diverter valve unit (perhaps something is sticking) and get a new one. but that will involve the faff of draining the whole central heating system.

Any better ideas?

[was8v]

Dave_ST220 said:

I feel your pain. I had this and there was a small piece of what looked like grit blocking the pipe in the diverter valve so it would only work when on full. I fixed that then 6 months later the little lever that operates the microswitch snapped, I phoned British Gas who fitted a new diverter valve, a new pressure guage, some other valve that was sticking and it was all sorted for £150 IIRC (parts alone were well above that!).

did you take out their cover then I presume?

[was8v]

cjs said:

When my Diverter valve went on my Potterton Puma, I changed the complete valve, all okay after. I did not have to drain down the system, although I do have isolating valves on the send and return feed. Valve was around £80 + Vat IIRC.

Yeah it looks like I don't have isolator valves (grrr). The boiler itself is a bit crappy (Sime Friendly) and I've just bought a new fan for it £120.

Just thinking about getting a more efficient new replacement than spending more on this.