Squeeling thermostatic mixer shower.

[ProDave]

Our main shower has a thermostatic bar mixer that takes mains pressure hot and cold water and mixes it to feed the shower head.

the original one failed (for the second time) so I've just bought another new one.

This new one squeels when you turn it on. Not just a quiet squeel, but an awfully loud, very very irritating high pitched squeel. Not something you want to listen to while showering.

After much fiddling, I have sort of got it under control, by almost shutting off the isolating valve for the cold feed. Now it only squeels when you first turn it on and once the hot water gets through the squeeling stops. but that's still not right.

Although it was bought as new, there's no instructions and I don't even know the make (not that I knew the make of the old one)

Is this common? It sounds to me it doesn't like our relatively high water pressure (about 3 bar)

I'll probably have to send this one back, but what can I do to ensure the next one works okay?

 

[Ray4438]

Is there a ball valve on the main cold feed to shower as it sounds that the mains is on to hard causing it to vibrate the washer in the mixer.

If no valve try turning the main stop cock down and see if that works. Have seen this before but turning pressure down usually sorts it......

 

[Sharpend]

Fairly sure you can get a pressure equalising valve which you fit inline on cold feed. ???

 

[SLIPSHOD & SLAPDASH]

http://www.talk.electricianforum.co.uk/plumbing-central-heating-forum-free-help-advice/11306-mixer-shower-screeching-grohe.html

 

[ProDave]

Okay, so we know the new bar mixer must be "faulty" or operating outside it's (unknown) specification.

But WHY?

Surely these things are MADE to operate on unvented mains pressure hot water systems?

I haven't changed the boiler or made any alterations. I just swapped the complete bar mixer assembly for another one that looks virtually identical, but this one does not like the high pressure.

By partially shutting the cold water isolating valve, and hence restricting the cold water flow, I have got it to the point that it only squeels until the hot water reaches the shower. So if I run the hot tap on the basin until the hot water gets there, then turn on the shower, it's only a few seconds of squeeling before he hot water gets to the shower then it shuts up.

But as I say that's only by restricting the cold water flow (not pressure) and a lot of faffing about.

So I take it I have to re work my plumbing (which has been fine since the house was built) or reject this one as faulty and try a different make?