Water pressure dropped in my shower

[lalalonglegs]

Our (thermostatic mixer) shower is fed by a Megaflo tank and the pressure has really dropped in recent weeks so that it is almost impossible to have a hot shower. The basin in the shower room still has good pressure from the tap and the pipework to the shower doesn't appear to be leaking (no water marks in the rooms below) - what can we do?

if all the other taps are OK (test the flow by filling a bucket and timing it) it's probably the shower mixer.

Start by taking off the squirty head and descaling it. Test at hot, cold and "override" settings. Look for any service valves that might have been changed.

If the knob or lever is stiff it may be wear or limescale.

Some, such as Aquaslisa round knob mixer, are very easy to fit a new cartridge. If it's a bar mixer it is probably not worth repairing, just replace it. This will all be much easier if it is exposed on the surface of the wall rather than buried under tiles and plaster.

Thanks for your advice, as ever, PJ. It is Aqualisa so that's a tick... the bad news is that it is concealed but a round knob not a bar mixer - are the round ones as difficult or should the whole mechanism slide out (somehow)?

there should be a round ring, probably white or chrome, round the knob. It might be sealed to the wall with silicone, but if you cut that, it should pull off, and if it has been installed correctly, it is possible to undo some nuts and remove the whole thing, or just take the front off and you can change the cartridge.

there are videos on youtube and elsewhere. This bloke is good.

yours is probably an Aquavalve, there are various models beginning with a 6 or a 9.

try www.aqualisa.co.uk/showers/identify-my-shower
Most of them are thermostatic, but there are also pressure-balancing models.

IIRC a new cartridge is in the region of £80, but try descaling first, and call their helpline to see if they think it's the cartridge at fault. They do last a long time, but hard water causes wear and scale.

btw you ought to have isolating valves allowing you to turn off the hot and cold supplies to the mixer. If not, or if they are the little cheap ones, I strongly recommend this Pegler. I'm always amused that the red one costs 50p less than the blue. It's full bore so allows water to flow without restriction, and is much less likely to leak.

the tee handle means you can turn it off with strong fingers, no tools required. they do ones with longer handles if you are weedy.

I'm in London so the water is almost solid with limescale . I'll try descaling but I'm pretty sure it's the mixer, now you've outlined the problem, as the drop was quite sudden and the flow is much stronger if I run it on cold.

save up for a water softener