Mixer shower not mixing?

lovestrat74

Any plumbers or knowledgeable people out there with any advice?

My mixer shower appear to be stuck at a certain mix even when I move it from hot to cold.

In order to not have a cold shower I've had to turn the water up on the boiler to 65 degrees. 

I've taken the knob off to see if it's the traction on the mechanism but no matter how far the brass thingy is turned the temperature remains constant.

Any ideas?

Adey

Scaled up inside? Have you got hold of instruction for dismantling and cleaning?

octatonic

Looks like the thermostat which regulates the cold/hot mix.
These can becomes scaled and stop working.

The easiest way to fix it is to replace the thermostat.
I get plumbers to do it because I don't want to fuck it up, but it can be done by a careful individual.

lovestrat74

Not wanting to sound like a muppet I didn't think a mixer shower has a thermostat, but a mechanism for controlling the hot and cold flow into the shower?

lovestrat74

Adey said:

Scaled up inside? Have you got hold of instruction for dismantling and cleaning?

I'll see if I can dig it out. I'd be surprised as it is less than a year old and we have installed a water softener too.

Adey

There is definitely a thermostatic valve in there. If you can't adjust the temperature it seems a prime contender for being the problem.

If fairly new, it could be some debris in it blocking it.

lovestrat74

Okay I've just watched a youtube vid to remove and clean the stat so I'll give it a go

strtdv

If it's a standard mixer rather than a thermostatic one then it's easy to replace, you remove the circlip and any washers and they unscrew. 
It works with 2 ceramic plates that slide over each other. 

Easiest way to get a matching replacement is to bring the old one to a plumbing supplies shop, as there are a number of variables (depth of the cartridge, length of the shaft for the mixer control to attach to and the number of teeth on the spline)

octatonic

lovestrat74 said:

Not wanting to sound like a muppet I didn't think a mixer shower has a thermostat, but a mechanism for controlling the hot and cold flow into the shower?

They are a thing and I am 99% sure that is thermostatic.

boogieman

Get the cartridge pulled out and you often find there are filters in the pipework that feeds the shower. They can get blocked up with scale or crud, particularly on the hot side. Clean them out and that might restore things. 

And yes, thermostatic valves are common in shower mixers. They stop the water temperature drifting up or down. 

maharg101

Descaling the shower head if it is scaled can restore the mixing function. Had this previously on ours. Soaked the head in white vinegar overnight, bingo, back to optimum temperature mixing.

boogieman

maharg101 said:

Descaling the shower head if it is scaled can restore the mixing function. Had this previously on ours. Soaked the head in white vinegar overnight, bingo, back to optimum temperature mixing.

Descaling the shower head would restore the water flow but I can’t see how it would affect the water temperature? 

Adey

I assume that the thermostatic part has moving elements in it, and it they are gummed up then it can't do it's job properly.

crosstownvamp

The thermostatic controller is usually a wax cartridge. Not sure how it works but I suppose the wax expands under heat and moves a valve. After some years the wax doesn't do it's thing so needs replacing. That's what's in the cartridge.

And do bathroom fitters ever think about making it easy to service these things later? Nope.

francer

Just sorted a similar issue for my mum, her shower was too hot. From the picture you posted you may notice that you can make probably 1.5 turns on the central splined valve when the control knob is removed, but when the knob is on you only get half a turn because the grey half circle thing restricts the range, i guess this is a safety feature. Can you turn the spline valve with the knob off until you get a reasonable temperature? If yes, do that and put the knob back on, if it’s still not quite right remove the knob and readjust as required until the range is suitable.

If that doesn’t work, you may need to start replacing stuff.

lovestrat74

Tried that @francer and the temp remained constant. I am going to have to remove it and clean it. Not great as the plate is siliconed to the tiles 

maharg101

boogieman said:

maharg101 said:

Descaling the shower head if it is scaled can restore the mixing function. Had this previously on ours. Soaked the head in white vinegar overnight, bingo, back to optimum temperature mixing.

Descaling the shower head would restore the water flow but I can’t see how it would affect the water temperature? 

I agree, it's counter intuitive, but sorted out the temperature control on our shower pump mixer.

fastonebaz

Yeah, replace the thermostat cartridge.  Dead easy

Turn water off
Unscrew and remove it
Screw in replacement
Turn water on

Other steps as per your mixer. 

Something like this or similar for your model. 

https://www.screwfix.com/p/bristan-thermostatic-mixer-shower-cartridge/9864j

Adey

lovestrat74 said:

Tried that @francer and the temp remained constant. I am going to have to remove it and clean it. Not great as the plate is siliconed to the tiles 

A thin flexy knife can be used to cut the silicone seal away.

lovestrat74

Cheers guys

strtdv

Cartridges are pretty cheap and depending on your system turning off the supply to the shower can be a pain, personally I'd replace the cartridge when I've gone to the trouble of getting it out rather than cleaning it and hoping it solves the problem for an unknown length of time