trevi ceramic shower + combi = erratic

[visionset]

I have a supposedly maintenance free ceramic trevi shower valve that I installed 9 years ago. Originally it was fed by a traditional gravity hot/cold stored water system. For a year now it has been fed by a new combi system that I've also installed. But the shower does not operate nicely at all now. It is very erratic and hard to control, with a very adjustment required to be at a sensible temperature. I don't suspect the cartridge as faulty and I thought the match of these types of shower and HW system were a good match. What can I do?

[John Rumm]

Just to clarify, has the shower always been a problem on the combi or is this new?

Hard or soft water area?

[visionset]

It wasn't as good as I'd expected when I installed the combi, but possibly it has got worse.

Hard unfortunately There is no descaler anywhere in the system.

[Steve Firth]

Get rid of the combi.

[John Rumm]

Mixers designed for low pressure will often work on high, but can be harder to adjust etc with dead bands in the temperature control and most of the action happening over a narrow range of control settings. Fitting a water saving shower head - or one that has adjustable pressure reduction settings (often accomplished by inserting small drilled plastic discs in the back of the head connection), can help make the mixer work better.

Taking the valve apart and chucking it in a bucket of DS3 might help then.

[Ed Sirett]

1 ) How well did you clean out the system (primary pipework) when you fitted the new combi? 2) You might find that already the limescale has built up to an unhelpful amount in the boiler. Check if the boiler is cutting in and out when operating the shower.

[visionset]

With an almost insane obsessiveness.

No the boiler does not cut in/out at all during showering, just stays on.

Ha:

W

[Ed Sirett]

In which case the problem is in the shower and you won't have to descale the DHW exchanger this year.