Temperature trouble with new thermostatic bath/shower mixer tap

sourpuss2021

I've just had one of these fitted along with a new bath and it's really causing me grief!   I understand the left-hand dial controls the flow rate.  The right-hand dial controls the temperature and there's a button to press if you want it go above 38 celsius.

However so far I have only be able to achieve two temperatures:  Freezing cold, or scalding hot!!

I honestly wondered if the plumber had connected it to the hot water at all, it was just producing cold water for so many minutes however much I turned it.

Then, only hot.  So that if I have a shower, I have to stand back from it and cautiously flick water on myself.

Does this suggest to you that the tap is broken?   It doesn't seem to be actually mixing the temperatures, only producing one or the other.   I believe any momentary variations in temperature I may have briefly experienced are more to do with the time it takes the boiler to fire up, than any actual successful mixing of the hot and the cold.

Should I be speaking to the plumber, or the plumbers merchants that sold me the tap?   What redress should I expect?   I bought the tap from them on the 1st by the way, along with a new bath etc, and it was plumbed in last week.   Even if they do agree there's a problem and offer a replacement (they're fairly local so could visit), the plumber obviously won't come back for free, and I can't expect the plumber's merchants to compensate for his double fee, can I?

Or perhaps I've just not understood how the tap/dial works and I need to try one more time.  I'll give it another go later.

rob7475

With most thermostatic mixers, you have to turn the termparture dial anti-clockwise to increast the temperature. When you hit 39 degrees, you then press the button and carry on turning if you want it hotter. If that's not working, there's a few possibilities:

How is your hot water provided? Do you have a combi boiler, or a gravity fed system or an unvented cylinder. Some units are not suitable for gravity fed systems I believe. 

It could be the shower itself that's faulty. It might just be the thermostatic cartridge. Your merchants should be able to supply a replacement. I'd ask your plumber to come and check his work (I can't see what he could have done wrong though). Unfortunately, if it does turn out to be the shower that's faulty, you'll be stuck with paying for the plumbers time - the merchants will only cover the replacement / repair of the shower. They don't have to cover labour for fitting.

sourpuss2021

Thank you for yoru quick reply!

The hot water is provided by a Vaillant combi boiler that was fitted last year.  It's a bit far away (down half a dozen internal stairs and round a corner).   The property is a flat in a converted house.   The shower is just an above-bath thing that was also supplied by the merchants along with the rail. 

It looks like the tap itself can be attached to a wall, but here I had the plumber attach it to the bath's pre-drilled tap-hole.  When I'm turning the temperature dial I'm doing it blind because there isn't a visible line on the body of the tap that indicates from which rotational position it's read.  I imagine this can be seen if it's mounted to a wall.

I will have another go with the dial in case I'm just doing it incorrectly.   Thanks again!

Chickereeeee

Turn the temperature control up to the stop (where you have to press a button to go further) and leave it there. That should be  close to the ideal temperature. Then turn the flow control to get a good flow. If the temperature remains incorrect after a couple of minutes, then there is a problem.
Possibly hot/cold reversed (hot is usually on the left pipe - is it)? Plumber should have spotted that though. Otherwise possibly pressure/flow from boiler too weak, or duff cartridge.

Nb: plumber should have checked for proper flow and temperature after installation.

Bendy_House

Reversed connections, as Chick'ee mentioned, ain't unheard of!

SourP, since you bought the mixer yourself, you will have to pay any labour to have it replaced. The merchant will/should replace it without question if it's at fault, but you'll still need to pay the plumber for their time.

Does removal entail going under the bath? Or can it be unbolted from the top? That'll likely will make quite a difference.

sourpuss2021

Thanks, both!   Plumber had a long day because he also had to replace some floorboards and drywall after getting the old bath out, so may not have checked everything exhaustively.   Yes I think removal would involve taking the bath panel off.   I'll take another look this evening and post again. He needs to come back to put the shower screen on anyway since he didn't have time for that either.

Apart from the temperature I have been quite enjoying not having a shower screen or curtain when I use this above-bath shower.  It's surprising how little actually splashes on the floor and how much better the room ventilates.  But I digress...

shiraz99

Can you post a pic of the mixer please?

Bendy_House

sourpuss2021 said:

Thanks, both!   Plumber had a long day because he also had to replace some floorboards and drywall after getting the old bath out, so may not have checked everything exhaustively.   Yes I think removal would involve taking the bath panel off.   I'll take another look this evening and post again. He needs to come back to put the shower screen on anyway since he didn't have time for that either.

Apart from the temperature I have been quite enjoying not having a shower screen or curtain when I use this above-bath shower.  It's surprising how little actually splashes on the floor and how much better the room ventilates.  But I digress...

A wee test. Run the shower in whatever manner it takes to run hot, and feel both sides of the mixer to judge what side the hot supply is coming from.
Laugh loudly if it's on the right.

Bendy_House

Other possible silly errors - tho' I'm not suggesting it's this - there could be flow restrictors fitted to cope with different system pressures, and one side was left out...

NSG666

While your snagging flush the toilet a couple of times to make sure it's not filling with hot water - wouldn't be the first to mix those supplies too.

BUFF

sourpuss2021 said:

The hot water is provided by a Vaillant combi boiler that was fitted last year.  It's a bit far away (down half a dozen internal stairs and round a corner).  

Whilst not discounting any potential fault (& assuming that there isn't a massive pressure differential between hot & cold supplies) a few things to bear in mind:
As you are probably aware it takes time for a combi to go from cold to providing a steady stream of hot water so you have to allow time for that. 
A combi will only be able to provide a certain amount of hot water at a certain heat rise from the supply temperature e.g. 9l at 30C rise - check what your is rated at. Any cold water mixed in additionally will, of course, increase volume but lower  the overall temp.
At this time of year the supply temp of water from mains will be a lot colder than in summer. (https://openresearch.lsbu.ac.uk/item/872v8 says that mains water in London varies between 5C & 20C over the year).
Additionally you probably have some heat loss in the piping (especially from cold).

N.B thermostatic cartridges are not absolutely instantaneous, they have a (hopefully short) response time