hot water backing to header tank even when water turned off All aspects of plumbing questions and answers, help, tips and information

[PEGASUS]

we have a hot water system that seems to have its own secret water supply! hot water cylinder is in a cupboard on the first floor, with a header tank in the attic directly above it. The problem is that warm water is backing from the hot water cylinder,up to the header tank. Although this in itself is annoying, as the over flow is directly outside my bedroom window, it is not the main problem. I have drained the header tank, and turned off the mains supply to it, and turned off the boiler.... the water is still backing up from the cylinder, filling the header tank and overflowing. I have just now turned of the mains to the house, I thought; there is no water coming in for the taps or the loo cysterns, yet, yet, water is still backing up back to the header tank from the cylinder! Is it likely that the hot water cylinder is fed from any where other than the header tank, since in normal times, as we use water, the ball cock in the header tank allows it to refill?
incedentally we have a condensing boiler which is serviced every year, and was passed as good, last week. I don't get it!

[plumbbob]

Various ideas spring to mind, but the answer needs information you haven't given. How many header tanks are in the loft? One two or more? If more than one, which one is overflowing? And by overflowing you mean pouring on to the ground outside the house type overflowing?

Is your hot water high pressure or low pressure?

Do you have single block mixer taps anywhere in the house?

[KEITH MARSHALL]

PEGASUS, I HAD SIMILAR PROBLEM, TRACED IT TO THE INTEGRAL CHECK VALVE IN OUR GRAVITY FED MIXER SHOWER UNIT.

THIS HAD FAILED AND WAS ALLOWING THE COLD WATER (MAINS) TO FILL THE HEADER TANK THROUGH THE OUT FLOW FROM THE TANK, VIA THE HOT WATER SYSTEM. RESOLVED THE PROBLEM BY FITTING A SEPERATE CHECK VALVE ON THE COLD WATER FEED TO THE SHOWER.

PRIOR TO FINDING THE SHOWER AS THE CAUSATIVE FACTOR, I CHECKED THE ONLY TWO OTHER MIXER TAP UNITS IN THE HOUSE BY ISOLATING ALL BUT ONE UNIT VIA THEIR ISOLATING VALVES AND LETTING THE SYSTEM RUN UNTIL THE HEADER TANK STOPPED FILLING BY THE BALL VALVE, AND THEN WATCHING TO SEE IF THE TANK CONTINUED TO FILL. REPEAT FOR EACH MIXER UNIT. HOPE THIS HELPS :?:

[rexton]

Various ideas spring to mind, but the answer needs information you haven't given. How many header tanks are in the loft? One two or more? If more than one, which one is overflowing? And by overflowing you mean pouring on to the ground outside the house type overflowing?

Is your hot water high pressure or low pressure?

Do you have single block mixer taps anywhere in the house?

Hi,
I note the member did not get back to you with the info requested. I have a similar problem which started (as far as I know, in the past week) i.e. hot water going into my cold storage tank, presumably from my hot water tank. Initially , I think this mostly happened when the boiler was running but it is more regular now without the boiler being on. The ball cock is working properly - already checked. I put my hand down into the large cold storage tank (which is a few feet higher that the central heating header tank and felt warm water at one of the outlets at the bottom of the tank. My plumber cant figure why/ how it is being pushed up in an open vented system. I have several mixer taps in the house and a shower pump which is only used for the power showers and only runs when the showers are turned on. Any ideas solutions would be appreciated.

[plumbbob]

One possibility is a mixer tap problem.

If the outlet is restricted, when anyone turns both hot and cold on together, instead of coming out of the outlet, cold water which is of course at high pressure is forced back up the hot pipe in to the header tank.

Some years ago, I fitted a mixer tap that turned out to be faulty. There was a hairline crack in the brasswork that allowed cold water to cross to the hot side even when both taps were off. It took until 7pm before the penny dropped and I realised what was going on.

[rexton]

Thanks Plumbob. Actually when my plumber came back yesterday evening..He had the same idea. He told me to close the valve to the kitchen sink hot tap overnight to see if the water in the cold storage tank was still heating up. After checking the cold tank this morning the water had not heated (or At least not noticeable) which would indicate that the tap is probably the problem. However, the tank is filling more than the level the ballcock allows. I also discovered that the cold taps in the utility and downstairs toilet are connected to the mains. So..I think we have only found part of the solution

[Tomsallagh]

Solved – The Header Tank (expansion tank) kept overflowing even after the ballcock and valve were replaced.
Background – this started to happen after the boiler and pump were replaced. When the (hot water) heating was turned on for a short while the header tank started to overflow. The heating engineer conducted an observation of the header tank whilst I turned on the hot water heating to see what happens. There was no water or drips coming from the vent pipe, yet after a short while the engineer could see the water level in the Header Tank rising towards the overflow pipe.
The cause turned out to be when the new pump was fitted the setting was set to 3 (there are three settings: 1,2,3). The engineer reset this to 1 as that was powerful enough for the pump to do its work efficiently based on pipe length, number of radiators, distance to Immersion tank etc. the setting of 3 was too powerful and thus pushed extra water into the header tank causing the overflow.
Follow-up - Having fixed the above problem, then thinking ahead, in order to prevent this ever happening again I decided to have the Header Tank replaced by a sealed ‘expansion vessel’ which makes the Header Tank redundant. Job done.