Water not coming out hot in shower - OK everywhere else

ThisIsWeird

Sumarokov said:

Apologies that the picture is a bit blurry, but I hope it does the purpose.

I cannot see the pipes, but the bathroom is right next to the kitchen (through the wall), where the gas boiler hangs, so very short route from the boiler and water supply to the shower itself.

There is no question of the hot and cold being mixed up. The cold does as it should, but the hot just comes out lukewarm and only becomes something approaching "pleasantly warm" when I am ready to finish my shower and jump out!

Thanks.

The way to check if it's been plumber in correctly - H&C - is to feel each pipe as they enter the back of the mixer. Which one heats up?

Ok, it's unlikely to be that, but it has happened on here!

Useful info that the boiler is close by - that helps. If you can, try and see if you can ID the pipes that head through to the shower - see if there are isolators on them.

Anyhoo, as Miser says, the most likely culprit by far is a failed thermostat. To replace this is a semi-challenging DIY job, which can go perfectly smoothly as long as the fittings aren't seized - which they often are.

An easier alternative is to replace the whole mixer, and very good chance you can do this for the same cost. This only involves undoing the two large nuts in front of the decorative collars, and lifting off the mixer. 

A few checks to ensure this mixer is a standard fit - measure as accurately as possible the distance between the two pipes as they come out the wall into the mixer, centre-to-centre. Use a marker pen to 'dot' the centre of each, and then measure.

But, first try the 'feel' test - tobesuretobesure.

ThisIsWeird

Fair chance: https://www.ebay.co.uk/itm/155729387732?hash=item244231e0d4:g:FEEAAOSwTdVk4wx-

Example of whole mixer, but dims would need to be checked: https://www.ebay.co.uk/itm/285563093706?hash=item427ce302ca:g:UUgAAOSwqCNlVx4q

Ganga

Can you also turn the hot tap beyond the normal setting ,you normally have to depress a pin to do this so you do not accidently scald yourself ,it would be interesting to see what temp the water comes out ,you can do this at arms length so you do not get scalded.

Sumarokov

ThisIsWeird said:

The way to check if it's been plumber in correctly - H&C - is to feel each pipe as they enter the back of the mixer. Which one heats up?

Ok, it's unlikely to be that, but it has happened on here!

But, first try the 'feel' test - tobesuretobesure.

So I checked and the left-hand side heats up really quickly. You can definitely feel it. Only what I do not understand is... where does all this hot water go? It is inches, seconds away from coming out the shower... but it is like it is going into some sort of Bermuda Triangle, lol.

daivid

The valve could be shutting out the hot, or if it is failing to regulate the mixing, the cold being at a higher pressure will dominate. When my mixer shower went on the blink it turned out an O ring that completed the seal between hot and cold intakes had deteriorated. By the time I'd found that out I'd already bought a new cartridge (and opened the packaging) so now have a spare.

greyteam1959

There could very well be a blocked filter in that bar on the wall.

ThisIsWeird

Sumarokov said:

So I checked and the left-hand side heats up really quickly. You can definitely feel it. Only what I do not understand is... where does all this hot water go? It is inches, seconds away from coming out the shower... but it is like it is going into some sort of Bermuda Triangle, lol.

Ok, so it's plumbed in correctly.
Why does that side get nicely hot? Because it only takes a tiny hot trickle at 60oC to make the pipe become hot.
Have you also tried Ganga's test - turn the hot control to its max, and then press the override button to allow it to go further - any hotter?
Also, when you turn the temp control, does it feel smooth, or does it stiffen up or feel rough in places?

Sumarokov

Ganga said:

Can you also turn the hot tap beyond the normal setting ,you normally have to depress a pin to do this so you do not accidently scald yourself ,it would be interesting to see what temp the water comes out ,you can do this at arms length so you do not get scalded.

I tried doing this today. The temperature did not come out any hotter, although it was slightly quicker in deciding to eventually move from "tepid" to "a bit warmer than lukewarm, but not much"!

In any case, I am grateful for the responses, as I thought at first I may have been doing some combination wrong on the boiler settings. I will go back and upvote all the people who were kind enough to answer this thread and will call in a plumber to have a look at the thing.

I am actually planning to have a new bathroom put in; I prefer a bath to a shower and there is just enough room. But I will not be doing this immediately, so it makes sense to get this sorted right now. I do not really go in for hot showers and shower cold at the end, but in winter you need a hot shower. Thanks.

ThisIsWeird

Summat clearly amiss. Going beyond the 'safety' stop should give a nicely hot shower - a wee bit 'ooooh!'.

Almost certainly a faulty cartridge, or debris in the filter (most have them built in).

If you plan to rip it out at some point, then I'd suggest a straight replacement such as the one I linked to will be the most sensible option - ~£50 tops for the mixer, and a very quick job for a plumber. He'd have to be happy going for a 'cheapy' like this, but I'd be happy to bet that the insides will be the same as mixers costing 3 times that amount.

Even when you fit a bath, I'd suggest also having a combi-powered shower over it - the vast majority of folk would want this, but clearly that's your call.

Please keep us updated with the outcome.