Water doesn\\\'t stay hot

karlrees · 7 Nov 2003

Hi there,

I've a Potterton Puma combination boiler which fires up okay when the hot tap is turned on, but fails to stay hot for very long. After 20 secs or so the water turns cold and then back to hot after another 20 secs. Makes a shower of any length rather hard work.

I'd be really grateful for any advice and also an estimate for any work required.

Huge thanks in advance

corgiman · 8 Nov 2003

difficult one to diagnose mate

whats the water pressure at the tap like???

karlrees · 9 Nov 2003

Cheers for your reply.

The boiler dial says the pressure's around 1.5 bar. The tap flow isn't too bad - although somethimes it comes out in 3 streams for some reason.

ChrisR · 9 Nov 2003

Faulty water temp sensor?

Do you live in a particularly hard water area?

karlrees · 10 Nov 2003

Yup. Live in East London, so the water is pretty hard.

I seem to recall that a plumber once said there was some kind of a diaphragm that controls the flow(?) and may need replacing. Forgive my ignorance if this makes no sense...

joseph · 12 Nov 2003

Hello There,

Does the hot water only do this when the heating is on, because the water in the boiler gets residual heat from the heating circuit and therefore comes out hot then goes cold as "new" water enters the boiler then warms up as normal. Ive only just had a combi fitted and it took me a while to work this out, although im not bothered as it gives me enough hot water for a wash.

I hope this helps you.

Joseph

ollski · 12 Nov 2003

does the water stay hot if you are, say, filling the bath or otherwise drawing off a lot of hot water and be a lot worse if you are just using the shower?

DAJ · 29 Jun 2006

Chances are that the heat exchanger is sludged up inside the boiler. You need to get this checked out (as I did) before assuming anything else.

Softus · 29 Jun 2006

1. When you open a hot tap with the CH off, does the boiler fire?

2. If not, does the flow switch LED (red) light up on the PCB?

3. If the boiler does fire, does it stay alight while the water goes cold?

4. When the water goes hot again, how hot is it?

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Water doesn\\\'t stay hot

DAJ

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