Shower not working properly - Please help!

[the moomin]

Any help on this would be greatly appreciated. I apologise for any terms or descriptions which are terrible!!

We have a shower that has been fitted for about 2 or 3 years. We didnt fit it. It is not electric. About 6 weeks ago the water pressure has been appalling. some days it is fine, others it is just a dribble coming out. WHen the pressure is bad, it makes a whistling noise.

I have checked that its not the shower head, but even when you disconnect the shower head pipe from the bit at the wall the pressure is still bad. The knob that you turn to change the temperature seems a little stiff, as does the knob for turning the water on. I have tried WD40 on them, but as I am sure is obvious to anyone who knows, that had no effect at all. Someone suggested turning the temperature knob up and down a lot as something could be stuck inside, that hasnt done anything at all, although it does appear that when its at cold the pressure is a bit better, when you turn it to hot the pressure drops again.

This may be a red herring, but sometimes when using the shower it suddenly goes cold. This has never happened before the pressure problems. I have checked the boiler in case of a drop of pressure there, but that all seems fine too.

We have normal water pressure to the taps and the bath in the same room.

Does anyone have any ideas what I can do next, or what it may be. I do not know what make of shower it is unfortuantely.

 

[hi-spec plumbing heating]

what shower mixer is it.
have you tried the filters or check if the non return valves are not sticking?
and the thermostatic cartridge don't sound to clever.

 

[the moomin]

Oh no, I am now about to sound really dim.
No I havent checked any of those things. How would I do that?
And also...how do I know what sort of shower mixer it is?
I apologise for not knowing anything here, my diy skills are improving due to my husband being rubbish at it, but its still not good - sorry!

 

[hi-spec plumbing heating]

the filters and valves are located in the back of the mixer total strip down.
any names or markings on the mixer valve ?

 

[the moomin]

I have not taken the shower apart to look at anything like that. I suspect that is going to way out of my depth.

Looks like i'm going to have to call someone out to it.

 

[hi-spec plumbing heating]

probably the best idea as it's all getting stiff. get new seal kit.
but you'll need to know make and model first.