DIY Doctor

HOT water from taps turning cold when turned full on

Postby time_wait » Fri Jan 30, 2009 12:39 pm

I get hot water through the mixer tap, but as soon as I turn the tap full
on in the hot position I get cold water.
This is true to a less degree with all the taps.(worse is the bath tap)
This was the case before I had the boiler serviced yesterday, by Corgi
They said it was due to the pressure but in other houses if you turn the hot water tap on that's what you get.
It seems I can only have hot water on if I am very careful with the water pressure coming vthrough the tap.
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Simply Build It

Postby htg engineer » Sat Jan 31, 2009 3:04 pm

Quite common on combi boilers, obviously the slower the water flows through the boiler the hotter the water will get, opening the tap fully the water passes through the boiler too fast for adequate heat transfer.

Check the hot water flow rate against the manufacturers instructions, it'll say what flow rate (litres per minute) and what temperature rise the boiler is capable of.

If the flow rate is right but the temperature isn't get an engineer to check and reset the burner pressures.

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Postby Steve the gas » Sun Feb 01, 2009 5:38 am

Of course resetting pressures needs to be done by an RGI
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