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By Lex Sanders
Dear experts,

I have scoured the web for a solution to my problem but sources everywhere seem to have out-dated or misleading/contradictory solutions so I am hoping an experienced plumber/technician here can help me out!

The problem
I have a mixed shower tap system on my bath but the shower only delivers scalding hot water when mixed, despite the taps working perfectly fine. I naively thought the issue was with the mixer tap itself and bought a new one last weekend although it hasn't fixed the issue.

Mixer tap: (suitable for all pressure systems according to spec)
Boiler: Worcester Bosch 24i/28i
System: The cold water comes directly from the tank in the loft and the hot water comes from the boiler down in the kitchen. I'm assuming this is called a Gravity Fed System?

I am an amateur at these things but I am under the impression that the cold water pressure is too low (or at least not equal to the hot water) causing the temperatures not to mix when using the shower. What I don't understand is why it works fine with the water coming out of the taps but the problem only occurs when pulling the stout to re-direct flow to the shower-head. The cold water pressure also seems to "look" and "feel" fine when coming out of the taps.

I think I need to add some sort of pump to the cold water pipe to increase pressure but I don't know where or what type! I would strongly prefer a DIY solution as opposed to having to do any large-scale work as this is a council house.

Please let me know if there's any more information I can provide!
User avatar
yup! you can only get out what you put in!!

you have is a pressure not flow problem 0.2 bar cold supply to perhaps 2-3 bar hot mains fed.
have you tried running low cold before adding hot? this will reduce flow but maintain lower temp.
fit a salamander boost pump to tap cold, but that will draw the tank dry after a short time.

baffles me why electric showers are not standard in rental tbh.

another solution:
what i did with a combi with the same tap shower as yours at a tenants property during the heat of the summer to the report of shower too hot......
turn the thermostat on the boiler down ;)
hot water secondary return

Just the info I was looking for. Thanks MD BTW, […]

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