Hot water taps running cold when on full

stevebantam

Hi,

we seem to have a slight problem with our hot water at the moment - for the last couple of weeks all the hot water taps have been running cold when fully turned on. The boiler fires up as normal and if the taps are only opened slightly the water runs hot as expected; however the more the taps are opened the colder the water gets. We have mixer taps in the kitchen and bathroom, and the same thing is happening on all of them.

Any advice gratefully received!

Steve

themull1

Mine was the pressure in my boiler. check what it should be, then check what it is and fiddle with the dial!

SailorSam

Check the pump. If the water pump is faulty it may be doing enough to push water around the system with the taps on low, but as soon as you need a full flow it fails.

Lgas

Combi boilers are designed to provide a temperature rise at a specific flow rate - the faster you run the tap, the faster the water is going through the plate heat exchanger and the quicker the heat transfer, so the faster the tap, the less time it has to warm up. If your plate heat exchanger is blocked with sludge on the heating side that can cause this problem, as the heat transfer is reduced even more, but this can also happen when a mixer tap is passing cold water into the hot supply.

If you have checked the pressure on the boiler is above 1 bar, I would get a gas safe registered engineer in to take a look.