Only lukewarm water at max setting; Thermostatic Shower

Postby novicehere » Wed Nov 26, 2008 3:17 pm


I have a thermostatic Aqualisa Shower (Aquavalve 609; fairly new) which is connected to a Ariston Combi Boiler (A23/A27 MFFI; Make: 2000)

The problem is that even when the temparture knob is at the maximum setting, all I get is lukewarm water. If I reduce the pressure flow a little, I get mildly hot water - but nowehere near what I would expect at max temparature.

The hot water in the taps/ basin etc is fine and comes out very hot. So I guess the problem is not with the boiler but with the shower? (Besides, we just had the annual inspection on the boiler and the engineer did not mention any problems).

I don't know the history of the boiler (or the shower) as we moved into this house only a few months ago.

Can anyone please help? I have been informally advised by a friend (not a qualified plumber or engineer) that it may be something to do with the thermostatic valve. Is that right? Might it need replacement?

I am new to the UK and a complete novice at DIY/plumbing.

Thanks a lot.
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Simply Build It

Postby bobplum » Wed Nov 26, 2008 10:07 pm

i think if you contact the shower makers you may get the installation guide on it and im pretty sure you can adjust the handle postion in relation to the spindle/settings to get more hot water out of it
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Postby gazwads » Thu Nov 27, 2008 8:06 pm

your mixer shower is passing, you need a plumber to fit a new shower mixer or fit a none return valve to the hot water pipe to the shower. hope this helps
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Postby novicehere » Fri Nov 28, 2008 2:40 pm

Thanks bobplum and gazwads.

I will call Aqualisa and ask them about the shower mixer (as well as the instalation guide).
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Postby plumbbob » Fri Nov 28, 2008 9:40 pm

According to the Aquavalve installation instructions:-

Step 7

"If the valve is being installed for use with a
gas fired instantaneous (multipoint) water
heater or a combination boiler, the cold
water flow regulator must be fitted at this
stage by insertion into the cold water port as
shown (the flow regulator is supplied in its
own pack)."

If this step has been omitted, the shower will perform as you describe. Download the instructions and remove the valve for examination. The reducers I have seem are the size of a penny piece, made of white plastic with a small hole in the middle.
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Postby novicehere » Mon Dec 01, 2008 12:03 pm

Plumbbob: I think that makes sense...Now my next challenge is to get a local plumber who will not charge me an arm and a leg to get this checked and fixed!

Thanks All.
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Postby plumbbob » Mon Dec 01, 2008 9:49 pm

The part you need (well think you need) is supplied with the shower valve and is not something a plumber will have in his box, or stocked by a merchant so discuss it with him before you are spending money.
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Postby novicehere » Tue Dec 02, 2008 7:42 am

Thanks plumbbob..

Well, I guess I should be prepared to order a new thermostatic valve then? (I don't have the original manual or the parts).
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Postby Barry Bunsen » Tue Dec 02, 2008 9:11 am

I had a similar problem with a thermostatic shower fitted to my combi boiler a couple of years ago. The cold water was at a slightly higher pressure than the hot water and simply forced its way back along the hot water pipe. Luckily I had access to the pipes near the back of the shower unit and could feel this happening. Had for example the themostatic unit been at fault the hot pipe would have remained hot but only let a restricted amount of hot water through. I fitted check valves on both pipes and the problem was resolved. Nowadays I thought most thermostatic showers had them built in. Hope this helps.
Barry Bunsen
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Postby plumbbob » Tue Dec 02, 2008 8:20 pm

If the shower is any good, I certainly wouldn't dump it, then I am well known for keeping any old rubbish (still got the wife lol).

Anyway, the Aquavalve is a current shower so the part should be available as a spare part from the manufacturers. You probably could even make one. If the valve is not buried in the wall, it is easy to access where this part should fit.
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