How do I stop water supply to feeder tank

[John P]

I have had an intermittent overflow from my feeder tank in my flat for some time. One plumber changed the ball valve and another changed the setting on the central heating pump.

I have been staying with a friend during the lock-down. Before I left I turned off the boiler and closed the stopcock where the water supply to my flat enters the building, believing that that would stop water entering the feed tank and so prevent any overflow.

I have now been told that there's an overflow again.

I had thought that the water supply to the feeder tank was from the mains. Could it in fact be from the water storage tank that sits above the hot water cylinder?

Or could there be any other way that the feeder tank is filling despite the mains supply being off?

I'd be grateful for any ideas.

 

[Roy_66]

Dear John,

I'm only an amateur plumber so I'll leave the best answer to the professionals here. Just some silly questions that might perhaps help a little:

Are you still isolating elsewhere, or now back in residence ? (and hence looking to run the system normally)

If you are in residence and running the system, are you able to safely look at the two tanks. Please do not go in the loft etc. unless this is an activity you are happy with, familiar with, and safe doing. It's not worth an accident.

Assume the two tanks are at the same level, and the one you are having trouble with is the central heating header?

How big is the leak ( drop or steady flow )

Personally I would be a bit wary of isolating at the main stop tap and leaving the central heating on (?)

If you are still isolating elsewhere how often do you check the property? (or do others do that)

As to what is wrong, perhaps the float on the new valve was not fitted correctly so water level too high, or its come loose. How big is the overflow leak (drip or steady flow ?)

Other thing with ball valves is you need the correct type, high or low pressure (but that said being a rank amateur, can't think why that would give a leak . . . )

E.g. (just Google if my link here does not work)

What is the difference between a High and Low Pressure Ball Float Valve

Best uses of each type and image of the nozzle hole dimensions to help identification

www.ondemandsupplies.co.uk

.

Cheers,

Roy

 

[Stigster]

A split/holed coil in an indirect hot water cylinder will cause the two header tanks to try to equalise in water level and cause this symptom of overflowing with the mains off.

 

[moonlight]

You stop tap must be letting by some water, and as Stigster says there is a chance the coil in the cylinder has split or has a hole in it and the two tanks are balancing the water level otherwise the over flow would eventually stop with no water entering the tanks.

 

[John P]

A split/holed coil in an indirect hot water cylinder will cause the two header tanks to try to equalise in water level and cause this symptom of overflowing with the mains off.

Thanks for your comment.

A split/holed coil in an indirect hot water cylinder will cause the two header tanks to try to equalise in water level and cause this symptom of overflowing with the mains off.

Thanks for your comment. I suppose the answer is to drain the system until I can get a new cylinder installed.
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You stop tap must be letting by some water, and as Stigster says there is a chance the coil in the cylinder has split or has a hole in it and the two tanks are balancing the water level otherwise the over flow would eventually stop with no water entering the tanks.

Thanks for your comment. There's no sign of water at the cold water tap, which is two floors above the stopcock. I suppose the answer is to drain the system until I can get a new cylinder installed.
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Dear John,

I'm only an amateur plumber so I'll leave the best answer to the professionals here. Just some silly questions that might perhaps help a little:

Are you still isolating elsewhere, or now back in residence ? (and hence looking to run the system normally)

If you are in residence and running the system, are you able to safely look at the two tanks. Please do not go in the loft etc. unless this is an activity you are happy with, familiar with, and safe doing. It's not worth an accident.

Assume the two tanks are at the same level, and the one you are having trouble with is the central heating header?

How big is the leak ( drop or steady flow )

Personally I would be a bit wary of isolating at the main stop tap and leaving the central heating on (?)

If you are still isolating elsewhere how often do you check the property? (or do others do that)

As to what is wrong, perhaps the float on the new valve was not fitted correctly so water level too high, or its come loose. How big is the overflow leak (drip or steady flow ?)

Other thing with ball valves is you need the correct type, high or low pressure (but that said being a rank amateur, can't think why that would give a leak . . . )

E.g. (just Google if my link here does not work)

What is the difference between a High and Low Pressure Ball Float Valve

Best uses of each type and image of the nozzle hole dimensions to help identification

www.ondemandsupplies.co.uk

.

Cheers,

Roy

Hi Roy,

Thanks for your comments.

The overflow has continued while the boiler has been switched off and the water supply turned off at the stopcock. The tank overflows from time to time a relatively small amount of water. The two tanks are about the same level but the overflowing feed tank may be a bit higher.

I think the source of the problem is probably a hole in the coil as others have suggested.