Combi fed mixer shower won't maintain temperature (oscillates)

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Hi
Living with three females and their patience with me is running out!
So far I have tried the following:
1) replaced mixer bar (would have just replaced inner cartridge thing but Triton said it was discontinued).
2) have fiddled with pressure reducing valve feeding bathroom (fitted by me yrs ago because I was advised to because our default pressure is particularly high)
3) have raised dial on boiler, although it hasn't needed this for its whole life.

My fear is that it's the boiler as running a bowl of hot water even from kitchen is temperamental. I don't regret replacing shower as I had to do this once anyway since fitting bathroom.

Questions.
Out of interest do pressure reducing valves have a certain lifetime? This valve does not feed kitchen or boiler in any way so isn't totally relevant.

Is poor water temp a sign that boiler is at end of life or could it be a standard repair?

I know I'll have to get someone in. Just hoping for advice first and may be something I've not considered

Thanks in advance
 
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One extra fact, when boiler fitted. It had a cannister on mains feed. Something to to with hard water. Unfortunately it's quite hard to access, and I'd have to cut through back of a kitchen cupboard. Do these cannisters need replacing. Do they simply stop purifying water or do they prevent flow in any way?
 
You have a blocked plate heat exchanger in your boiler.
You may be capable yourself or may need a pro.
 
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You have a blocked plate heat exchanger in your boiler.
You may be capable yourself or may need a pro.
Thanks for the quick reply. I would probably get a pro but I am flattered that given what I have done, you think I may be up to the job. I'm assuming therefore that this would be the type of repair that doesn't need gas.
safe. Ie I would never get involved with that side of things.
Final question before I start googling to educate myself.
Is this a part that needs replacing or is it a blockage that can ve manually cleared in some way?
At present I have no idea what it even looks like.
PS I have taken cover off before when I redirected a wire and fitted a thermostat which works fine. Obviously this was just electrics. Just saying I'm not afraid to have a look around. Realise that the law is tightening up on householders basically doing anything in kitchens.
 
Do all hot taps in the premises run hot ,then cold, then hot,then cold
repeatedly ? If so change the plate hex.
 
I don’t know that boiler so without looking can’t say whether or not you can undertake the work without qualification.
However if you are competent and know how to test the seal integrity if required you can can crack on in your own home.
Personally with your amount of knowledge I’d ask for recommendations from your friends or colleagues of a good repair man to sort for you.
Cleaning is possible but not always successful.
Good luck.
 
There are a few things in that boiler that can cause this, where in the country are you , might be someone from here who could help you out
 
Do all hot taps in the premises run hot ,then cold, then hot,then cold
repeatedly ? If so change the plate hex.
Yes, seems to be. By plate hex I assume you mean what I've just seen on YouTube, a metal unit about the size of a TV remote with in out for water and in out for radiators. Thanks
 
Dont know anyone personnally in your area but hopefully someone will, could be your plate heat exchanger, but there are other things it could be too, doesnt sound like it has been properly serviced for a while
 
I don’t know that boiler so without looking can’t say whether or not you can undertake the work without qualification.
However if you are competent and know how to test the seal integrity if required you can can crack on in your own home.
Personally with your amount of knowledge I’d ask for recommendations from your friends or colleagues of a good repair man to sort for you.
Cleaning is possible but not always successful.
Good luck.
Thanks again. Will probably have a careful look myself, anyway just out if curiosity. Depends on accessibility. Probably get someone in. But of course if everyone's booked up, then I might have a go. Will find out how much new part costs. Did see a video which showed that cleaning them can buy some extra time but isn't the total solution. Thanks again.
 

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