Advice please re-Mixer shower - Plumbing Forum | Plumbers Forums

matt_posh · 22-08-2008

Hi,

I'm after a bit of advice please. I'm just a house owner with very little knowledge of plumbing!

We've recently had a Mixer shower fitted (professionally by a Corgi plumber!) and we can't seem to get it to work correctly.

First of all, it was outputting water so scalding hot you couldn't even put your hand under it. I read the installation manual to find he'd plumbed it in wrong and the hot pipe was on the right when it should be on the left. I managed to change these around so the pipes are now going into the correct places.

HOWEVER now it's only producing cold water. The temperature knob has no effect (I've also taken the knob off and used the valve to adjust the temp - to no effect!)

I've rang the shower manufacturer (Bristan) and they suggested turning it on at full temperature while turning the bath and sink cold taps on to see if the shower temp changes as it'll then be something to do with cold water pressure over-riding the hot. I've done that and it hardly seems to change - hot water is getting as far as the bar on the shower but it doesn't seem as if it's being allowed through the bar.

I've also had a look at PRV's on the internet and I don't see how or where one of these could be fitted anyway. The shower is taking it's water from a T joint to the bath taps in 15mm white plastic pipes - surely a PRV is going to be too heavy to be fitted on there??

I'm not really sure what to do now as I'm reluctant to call my plumber back as he appeared to fit it wrong in the 1st place!

Any help or advice would be greatly appreciated!

matt_posh · 22-08-2008

Yes and yes (assuming you mean cold water coming out of the shower when on fully hot!)

Thanks for the reply.

matt_posh · 22-08-2008

I don't think so, not without putting a stopper thing onto the hot pipe anyway.

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

is it a bar mixer valve ?
i would try checking the one way valve on the shower it may be jammed shut and not letting the hot through if the pipe is hot to the mixer

This is the shower

Buy Cascade Manila Thermostatic Mixer Shower. at Argos.co.uk - Your Online Shop for .

Is the "one way valve" the one underneath the temperature knob cover??

Also what I've noticed since I posted the 1st post is that the hot water pipe to the mixer is hot for a couple of seconds but after a short period of time the (combi) boiler just fires off again. Is this because no hot water is being accepted or could this be something to do with it?? It's fine to the bath taps though which is where the shower is taking its water from.

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

the boiler will shut down if no water being taken or let through.

where the mixer valve secures to the wall is two 3/4 chrome nuts one on cold/hot.
is the hot side hot aswell as the pipe ?

if you isolate your main stopcock and undo the two nuts remove the mixer and look up the two holes on mixer and their should be ttwo filter washers and under them is the one way valve.

I can feel a very slight warmth on the hot side chrome nut, but I wouldn't say it's hot.

I'll have a look at that one way valve thing in a bit when I pop home.

Thanks for the help, I really appreciate it.

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

it sounds like the hot is getting to the one way valve but not through.

That makes sense - as (as I said in the 1st post) when the pipes were connected the wrong way round, the water was scalding hot and no cold was coming though.

Now I've swapped them around to the correct way, I'm getting only cold water and no hot - so it must be the valve on that side. I'll have a fiddle when I get home and post the outcome later!

Cheers.

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

its a poss but when you connect a thermostatic mixer up the wrong way it will pay havoc with the temps anyway as the hot will be going in the wrong way to the thermostatic cartridge inside and you get unsteady temps.

So if it was the wrong connection which has caused it and the thermostatic cartridge inside is knackered, how can I fix that??

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

the thermostatic cartridge should be ok. it takes more than that to knacker them.
try the valve first thats what i would opt for then we'll go from there.

Right then, I've checked the valves that you mentioned and they all seem fine. I also re-set the temperature gage so it should go to a higher temp than before. The shower is now all back together.

HOWEVER I've now noticed something else which may help towards diagnosing the problem.

When I turn the shower on a tiny bit (literally the least powerful it can go) the temp is fine and hot water is coming through as normal however when I turn the power knob up to the type of speed you would normally shower at and above, the heat dissappears, the water just goes cold and the boiler goes off.

Would this suggest that the cold water pressure is too high and is over-riding the hot? Meaning I need to get a PRV fitted??? EDIT - although that wouldn't explain why when the pipes were the wrong way round, the water was coming out scalding hot.

My head hurts!

matt_posh · 22-08-2008

The cold taps upstairs in the bath do appear to be more powerful, the sink in the bathroom seems about the same and in the kitchen the cold is a lot more powerful than the hot.

Is the dhw setting the temp control knob on the front?? If so that's just below being the highest it can be.

matt_posh · 22-08-2008

Quote:

Originally Posted by ajs heating

it does sound like a pressure problem.
check your shower manual as you sometimes get what they call a flow resrictor to fit into the shower mixer if the cold is over powering the hot.

No mention of a flow restrictor in the manuel.

The only mention of pressure is that It says that the required pressure is Min 0.1bar and Max 5bar. Maximum recommended imbalance between hot and cold pressures should not exceed a 5:1 ratio.

I've no idea how to check if I have the correct pressures going to it or infact how to change the pressures. Looks like I'll have to call someone out - bugger!

Any idea what the charge will be for getting someone out and sorting it??