Thermostatic shower problem diagnosis

[rumba]

Hi Guys

I have a new shower, but it only runs extremely warm or extremely cold.

Background:
- We have a Vaillant VCW 242E combi boiler
- The shower is completely new, it's an exposed thermostatic mixer with a large pan head.
- The shower has not worked properly since it was first installed a week ago.

We've had the bathroom re-done by builders who knocked out walls between the old toilet and bathroom to create one big bathroom, which enabled us to build a new stand-in shower away from the bath. They did all the new piping, but left the pipes for the shower capped off so I could finish the shower tiling before i connected the exposed thermostatic mixer shower tap.

When the shower turns on, it takes a while to warm up as the gas boiler starts up (nothing unusual there, takes about 30 seconds at most). However, the shower seems to be overcompensating with the thermostatic valves inside. It gets to the point where i can have the shower set to the coldest setting, but only boiling hot water comes through. Also i could have it set to the warmest setting, but only cold water comes out. it's like, once the shower gets going, it decides by chance whether it'll be cold or warm, then sticks to that no matter what you change the temperature setting to. turning the temp dial has no effect on the temperature or on the pressure/flow of the water coming out, but you can tell that the dial is not broken. it is moving something inside as there is resistance to the dial when the shower is turned on.

It's like it has a mind of it's own.


if i touch the water pipes coming out of the wall, i can feel that water is only travelling through one of the pipes, the other will only have a trickle. This doesn't happen until the water gets hot. e.g. turn on the shower, and both cold and luke warm water enter the mixer unit from both pipes. however, as the water gets hotter, it will either start to cut off the cold supply, or the hot supply will dwindle to nothing.

I wanted to rule everything out before i take the shower apart and send the mixer back to the shop where i bought it.

is it likely that the shower unit could be broken? is it likely that the thermostatic valves in a mixer unit can get stuck. i can't think of anything else which could cause this problem.

we have a mixer tap on the bathroom sink and bath, which both work fine. it doesn't look like we have any pressure problems with our hot water, as i've always thought it was quite constant before, and the amount of hot water is sufficient to get a good flow.

does anyone have any suggestions? it's driving me mad! i can manage not being able to have a shower, but the wifes nagging at me every day is starting to get tiring. she seems to think that just because i have the skills to connect a shower, that i'm a fully qualified corgi plumber! To be honest, i'm absolutely fine with basic or even advanced diy skills, but i'm beginning to feel out of my depth now.


I need help or suggestions as to the cause of the problem.

If you require more information to diagnose the problem, give us a shout. I'll come back to this topic regularly for the next few days so it doesn't die a death.

Oh, and thanks for any help you can provide!

 

[kevplumb]

are you sure the hot and cold are not crossed

whats the make and model

 

[rumba]

does it matter which way the hot and cold supply is? there were no instructions with the mixer tap to suggest this.

currently the cold is on the left and the hot on the right, as you look at the shower.

i wouldn't be able to get at the pipes without ruining my mosaic tiling. i'd have to cross over the cold and hot supply nearer the source, if that was the case. with limited space, is it possible to do this with flexible braded hosing? is there any way of telling if this is the problem before i go and knacker everything?

the shower is a jasmin exposed chrome thermostatic mixer from plumbworld. looks like they don't sell it anymore, but it's similar to the following design, i.e. not a bar mixer.

http://www.plumbworld.co.uk/1220-2883

 

[kevplumb]

convertion is hot left
cold right
and yes it is important

 

[rumba]

thanks for the speedy reply kev.

so what do you reckon is the easiest way to sort the problem.

can it be done by just connecting 2 lengths of flexyhose (e.g. like you get at the taps), or will it need to be done more professionally.

reason is, i'm gonna only have a small space in which to switch the supply over.

 

[rumba]

would something along the lines of this suffice?

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=92168&id=14767

 

[kevplumb]

yes might be a bit restrictive tho
if you can get at the pipework somewhere else other than at the shower compression will be a better job

other way is to turn the mixer so the outlet is at the bottom

might be easier

 

[ChrisR]

DO look carefully at the mixer. Often the lever(s) can either be fttef the other way up or can be used upside down without a real problem.

SOME mixers can even be twiddled inside to reverse the H & C.
Have a word with Plumbworld. Though it should be in the instructions anyway. They might give you a number to call at their supplier.

If you do end up swapping pipes, you needn'r worry too much about restriction as you're on a combi.

 

[kevplumb]

SOME mixers can even be twiddled inside to reverse the H & C.

the mira can dunno about the posters

 

[rumba]

many, many thanks for all your help.

i had a look, and the mixer had a secret compartment on the bottom, which was difficult to see as it's got a chrome plug consealing it.



after further investigation and tinkering, i managed to take it off, reverse it all, and stick it back on.

it now leaks as i don't have an allen key big enough to tighten one of the parts (and i didn't want to round it off), but after a quick investigation, i now have hot, cold, and everything in between!!!



admittedly i now have no water in the bathroom as i've had to turn the water supply off, but given 24 hours, a trip to b&q for a large allen key, and a bit of ptfe tape, i'll be ready for my first shower.

can't thank you enough. not only have you saved me money getting a plumber (my next resort), but the missus is back from a business trip on monday night, so i've got just enough time to get it fixed to collect my reward.

 

[kevplumb]

thanks for the feed back you wouldnt belive how many dont bother



enjoy

 

[rumba]

no problem.

enjoy the rest of your weekend