Will a PRV solve this?

[Pompeyblue]

Hi everybody

I'm a newbie so please be gentle!
first off I'm not a plumber but can do the basic plumbing jobs, but am stuck with something that I hope you can help with before I buy any parts.

Our thermostatic shower is rubbish. It won't mix well at all, and never has!
the plumber that installed it over a year ago has vanished...
And it's got to the point that I need to sort it. At first I thought maybe the cartridge had failed so replaced that and the washer which the manufacturer recommended. Still it's either super hot or super cold! (The thermostat button was actually broken so it need need replacing).
it seems to me that the cold water has more pressure that the hot so they dot mix that well and small turns make massive changes in temperature.
The hot water comes from the combo with the cold mains fed. If I fit a PRV on the cold below the shower will that make any difference? Or maybe a PEV?.
Anything I can check also?

Thanks for your help!

 

[Plum Bob 66]

I think in the first instance you should try a a single check valve on the hot pipework leading to the mixer as it would seem the pressure of the cold is pushing the hot back up the pipe. However I would have thought that the pressures were balanced if coming from a combi. Might be worth doing a pressure test to check to check for any in balance then fit PRV to bring them in line as you have suggested.

 

[Avatar]

Your plumber should have checked the pressures before fitting a thermostatic - it may have been better to have a simple mixer if the pressures are that different.

it may be good to work out what they are before trying anything else as it seems like you have been pouring money into this one . . . . .

Are you sure your hot supply is from a combi as this would mean that pressure should be fine (unless it is a very old combi!)

Usually you see this problem on places that has hot water cylinders - I had one once that had less than 0.1 bar of pressure on the hot side . . . .

You still might be best to get a proper plumber in - do not get just anyone! No builders or handymen . . . ..

You need someone to come and check the problem, find a solution and do the fix - probably you can get someone in to assess in initially without any outlay.

Once you have a quote/estimate in place you can go from there - get a couple of guys to look at it to compare.

It is hard to tell the problem without seeing it however!

 

[tamz]

A pressure equalising valve will fix it

 

[MrMeek]

on a mixer valve if the hot and colds are not the right way round, hot on the left cold on the right, this can also cause the problem. I found this out the hard way when installing on and just assuming the pipes were the right way around, check that they are the right way around before buying prv's etc, if they are the right way around put a prv on and regulate it.

 

[MrMeek]

and that fact you say it has never worked properly might suggest they are the wrong way round to, but check this first before wasting money on fittings

 

[Pompeyblue]

Thanks for the many replies!

I think i will fit the check vlave but after i switch the hot and cold.

MrMeek you are right, the hot and cold are the wrong way around.... The plumber said it was OK before he left the county!.. Its the same for the sink and bath. And when i pointed out that the cold tap on the sink does hot, he just took the heads on and swapped them....

Question is, can I just swap them under the bath using some flexi hose as I cant get behind the thermostat.. Ill do it on the pipes going up to the mixer. Not worried about the sink and bath right now.

Thanks!

 

[MrMeek]

you dont need a prv or any fittings you just need the hot and cold the right way around!, under your bath i presume it will tee of from your bath taps to supply shower see if you have enough room down there to adjust the pipe work first. if I was you don't use flexis yes their easy to install but could cause problems later and they will reduce the flow, either use copper or jg speed fit, if your not good at soldering or bending etc go for plastic remembering to put your inserts in!

no problem hope you sort it

 

[MrMeek]

or if possible do you know where the hot and cold pipe runs enter your bathroom? it could be easier getting to them and swapping them around then you will have everything the right way round?, and does that mean your toilet fills up with hot water?

oh and the check valve thing what someone suggested, no need for it and if its a new mixer it will already have check valves inside the mixer itself

 

[Plum Bob 66]

or if possible do you know where the hot and cold pipe runs enter your bathroom? it could be easier getting to them and swapping them around then you will have everything the right way round?, and does that mean your toilet fills up with hot water?

oh and the check valve thing what someone suggested, no need for it and if its a new mixer it will already have check valves inside the mixer itself

Yep good point, does it work in reverse.