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Header pressure tank overflowing

Posted: Fri Apr 03, 2009 2:09 pm
by Jeremy Sinclair

I have a plastic rectangular hot water tank in the loft that I believe is acting as a hot water pressure tank. There is also an insulated hot water tank in the airing cupboard of the bathroom below.

This pressure tank has a ball valve to control the water level and is overflowing quite continuously when the heating / hot water is on.

I think that I just need to alter the ball valve settings, but have not been able to do this as the water is hot. Also this tank is not properly insulated and so I think it might need to be replaced.

Please advise.

Posted: Fri Apr 03, 2009 11:05 pm
by stoneyboy
Jeremy Sinclair,
Your tank in the loft should be cold - you clearly have a serious problem and I suggest you get a plumber in before the loft tank starts to leak.

Posted: Sat Apr 04, 2009 4:58 am
by Steve the gas
Hi Jezza,

This is not good at all, its over pumping, so if your pump has speed settings slow it down.
As for the ball valve - bend it downwards if it is a metal one- to reduce level.


Posted: Sat Apr 04, 2009 9:28 am
by rosebery
You should have a small tank as F&E for your CH and a large tank for domestic water storage?

Which tank is warm / hot? It makes a difference as the cause is not the same?

Guessing for a moment that its the large CWST from your description the commonest reasons are:

1. Boiler or immersion stat too high. Water is boiling in the cylinder and rising up the expansion into the CWST.

2. You have a mixer fitted which has cold mains and hot from the cylinder. The cold is at far greater pressure than the hot, overwhelms it and forces the hot water back into the tank where it has nowhere to go except up the expansion pipe into the CWST.


Posted: Sun Apr 05, 2009 12:23 am
by plumbbob
When you say the tank is overflowing, what exactly do you mean?

Is the water overflowing from the copper expansion pipe into the plastic tank or is the tank itself overfilling and overflowing down the pipe to outside?

As everybody else says, get this problem fixed as the hot water in the plastic tank could cause it to fail suddenly.

Posted: Mon Apr 06, 2009 9:37 am
by Jeremy Sinclair
Thanks for your comments and advice.
I have bent down the ballcock so tank no longer overflowing :lol:
and will call plumber to look at this in due course.

Any advice for plumber in South Croydon?

Posted: Mon Apr 06, 2009 11:37 pm
by rosebery
"in due course."

Not nearly quick enough if its the CWST that is getting hot. A child was killed not that long ago because a stat had failed. Google article ""

Once again which tank is it?????