DIY Doctor UK DIY Forums

Hi all, I have had a look around and can't find a post regarding this.
We have a mixer shower, connected directly to the boiler.
The temperature control has become increasingly sensitive; tiny adjustments make massive difference in temperature. Over the last year we have had to increase the setting to maintain temperature. Before I risk taking the unit apart i wanted to check for advice/see if my diagnosis is correct.
We live in Leicester which has very hard water. Is it possible this problem is due to build up in the thermostatic valve forcing us to open it more and more to allow the same flow of hot water.
If this is so, is that something I can DIY fix by taking out the valve descaling/cleaning it and reinstalling it?

Did you find an answer? We have exactly the same problem. The shower used to work fine, then we had symptoms like you. We used to be able to improve things by leaving the temperature setting at 'fully cold' when the shower was not being used. Even that doesn't work now.
Thanks
Nick

No haven't had any replies yet, yours is the first comment since I posted.
Our problem remains.

Hi,
Thanks for the reply - I seem to have fixed ours.

We have a water softener but still, scale build up was the problem. It was not hard to fix for our type. There are hundreds of different types on the market.
For us....
We had the bathroom installed only a year previously and the plumber had put one of those little inline screw driver flat blade shut off valves on the supply pipes to the shower that we could get to via the airing cupboard (alternative is to drain down system to below shower level)
Plugged the shower plughole so that no bits could rush down there when I turned my back.
Undid the two big nuts holding the bar shower to the pipes/wall.
Caught the rubber washers with integral mesh filters.
Took the bar mixer to the work bench and dismantled.
Taking someone else's pic off another forum ('cos I didn't take one sorry).

Ignore the red arrow - he thought that his bar was stuck but reading online the bit he's pointing to only moves 0.6mm at most.
For me, I took out the circlip at 1.
Tapped the end 2.
Then 3. (attached to 2.) popped out with but had loads of scale jamming it into the housing. Then managed to separate 2 and 3 so that when you twist 2, 3 moves back and forth.

All bits dropped in descaling solution then scraped and smoothed with 1000 grit wet/dry paper.
Generally, the whole mechanism was cleaned up.
Put it all back together with a load of this stuff lubricating the moving parts with:
https://www.toolstation.com/plumbers-grease/p34053
Popped it back in the shower and it works like new again - lovely smooth action. If it goes again I'll redo.

I suppose the summary is:
Depending on your valve type: Dismantle as much as possible, drop into descaler, clean, reassemble, cross fingers.

Hope this helps you or others

Good luck

Nick

Hiya

I think we solved our issue

There are hundreds of different types of valve on the market so don’t know what your type is. This is what I did:

Turned off shower water supplies (easy for us as plumber had installed the little micro screw driver blade valves on the supply pipes when the shower was installed, otherwise you can drain down your system)
I bunged the plughole in case any parts did a ‘finding nemo’ when my back was turned.

Undid the 2 big nuts that held the bar shower to the wall, catching the pipe washers with integral wire filter mesh

Here’s a pic of the inside of the valve (nicked from another chap on another forum ‘cos is didn’t take a pic – sorry)


He thought that the bit pointed to by his red arrow was jammed but actually it’s only supposed to move 0.6mm max.
My problem was that the rest of the mechanism was bunged up and scaled up.
I cleaned all the bits then removed the circlip (1) tapped gently with a hammer on (2) so that (2) attached to (3) popped out. Then cleaned and managed to separate (2) and (3) so that when you twist (2), (3) moves back and forth.

I dropped everything into a descaling solution. Then cleaned/scraped everything clean and smoothed some parts of (3) and the housing with 1000 grit wet/dry paper.
I reassembled everything and lubed all the moving parts with:
https://www.toolstation.com/plumbers-grease/p34053
Reattached to the pipes, switched on supply and everything worked like new – lovely and smoooooth.

Enjoyed a nice Goldilocks shower –
I guess that the advice is – depending on your model, dismantle as much as poss, descale, smooth, relubricate and cross fingers.

Hope this helped you or others

Nick