Shower mixer and lack of hot water

8 Mar 2008
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United Kingdom
I have a shower mixer. I also have lots of hot water in the tank. When I use the shower the hot water doesn't seem to get very hot. Does this mean the mixer is broken. The hot water tank and the shower are on the same floor, does this matter.
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COUld be the HW is too hot - cavitation
or the cartridge in the mixer is dud
or the pump is sucking air down the HW side.
All are common.
depends what mixer it is, thermostatic or manual.
have you checked the hot pipe to the mixer is hot ?
check the filter.
if thermostatic poss the cartridge is stuck.
The hot water pipe to the shower mixer is hot and is fed into the mixer from below. The cold water comes in from above. Would this make a difference?
I can see a way of getting into the mixer to check it. I may have to remove the whole thing.
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If the hot water is gravity fed, and the cold is at mains pressure, many mixers will have a tough time coping with the unequal water pressures.

The position of the hot cylinder makes little difference. It's the position of the cold storage tank feeding the hot cylinder that establishes the hot water pressure available.

The best results are usually achieved by running the cold feed to the mixer from the cold storage tank. Adding a pressure reducing valve to a mains cold feed may improve matters.

A lot of the brassware on the market is made for high pressure systems, and will not operate satisfactorily on the low water pressure available from gravity systems. A shower booster pump can boost the pressure, but can't be used with a mains pressure cold supply.

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