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Discuss Leaking Cold water storage tank and overflow in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
3
Hi there Hoping for some advice on a plumbing issue. Bit of background - currently I am not using my gas central heating system. The system is 20+ years old and kept breaking down and various plumbers visited and fixed problems but advised system flushes or a range of options - essentially the conclusion is I need to replace the gas central heating system and am currently putting money aside to replace with a combi-boiler system in the near future. At the moment it is a cylinder / cold water tank system. So for now am getting by with electric heating and electric shower and hot water tap. Recently my overflows started running. Mostly the one from the eaves ( assuming cold water tank) but occasionally the one lower under my first floor bathrooms . Got a plumber out who replaced the ball float valve in cold water tank. However the overflow kept running. He investigated and seemed confused as to the issue and the set up of the system. He left saying he would be in touch but despite calls has not. So I have been left with having to turn my mains water off and only putting it on for short periods for showers, washing, toilet flushes etc then switching off again( the patio was flooding so couldn't just leave the overflow running all the time) . This morning having put the water on for showers etc and noticed dripping to find water coming through ceiling. Switched mains off and its appears to be coming from cold water tank through cupboard where cylinder is and to ceiling underneath. Caught quickly so damage minimal but need some advice as to what could be the issue and what needs fixed. Not quite in a position yet to get the system replaced so what are my short term options ? And why is this happening? Now afraid to put water back on at all - obviously not a situation that can be tolerated. Will get another plumber but given the confusion of previous one would be very grateful for some thoughts and advice. Would removing the cold water storage tank and cylinder be a solution in the short term before the full system is replaced? What are the implications? Any help gratefully appreciated.
 
Messages
887
1. It is quite likely that you will have three overflow pipes:
1a. One from the main cold water storage cistern (CWSC) in your loft.
1b. Another from a small "Feed and Expansion" (F&E) tank, also in your loft. This copes with the feed of water from, and the expansion of water when heated, related to your central heating system.
1c. The final being the overflow from the WC cistern. This is likely to be the one under your first floor bathroom.
2. Overflow pipes are there to warn you when a cistern is getting too much water in it.
3. The CWSC can overflow when:
3a. The float valve which cuts off the incoming cold mains water fails. This would be a continuous overflow when the mains is on.
3b. The hot water cylinder overheats. There is a pipe over the top of the CWSC in an inverted "J" shape, called a vent pipe This is a safety device which lets excess water from the hot water cylinder (HWC) flow into the CWSC. Because any such inflow does not pass through the float operated valve, it will cause the overflow to operate, unless sufficient water is drawn from the CWSC to balance the amount coming from the vent.
3c. In very rare circumstances if there is a fault in the HWC, which allows water to backfill into the CWSC.
4. The F&E can overflow:
4a. The float valve which cuts off the incoming cold mains water to the F&E fails. This would be a continuous overflow when the mains is on.
4b. The boiler overheats. There is normally a pipe over the top of the F&E in an inverted "J" shape, called a vent pipe This is a safety device which lets excess water from the boiler flow into the F&E. Because any such inflow does not pass through the float operated valve, it will cause the overflow to operate, unless sufficient water is drawn from the F&E to balance the amount coming from the vent. Such a fault is often caused by blockage in the boiler's primary water circulation circuit
4c. The pump which circulates the water from the boiler to the hot water and central heating circuits causes the system to "pump over" into the F&E vent. This is most often caused by the same problem as 4b.
5. The WC overflow operates if there is a problem with the float operated valve in the WC cistern. This will nearly always be a constant overflow except while the cistern is refilling after being flushed.
6. Removing the CWSC and HWC could be done, but is not just a question of capping a couple of pipes.
7. You need to get someone to identify and fix the problems you have, particularly the latest "through the ceiling" leak, which suggests either a very significant leakage problem or one or more blocked overflow pipes.
 
Messages
3
1. It is quite likely that you will have three overflow pipes:
1a. One from the main cold water storage cistern (CWSC) in your loft.
1b. Another from a small "Feed and Expansion" (F&E) tank, also in your loft. This copes with the feed of water from, and the expansion of water when heated, related to your central heating system.
1c. The final being the overflow from the WC cistern. This is likely to be the one under your first floor bathroom.
2. Overflow pipes are there to warn you when a cistern is getting too much water in it.
3. The CWSC can overflow when:
3a. The float valve which cuts off the incoming cold mains water fails. This would be a continuous overflow when the mains is on.
3b. The hot water cylinder overheats. There is a pipe over the top of the CWSC in an inverted "J" shape, called a vent pipe This is a safety device which lets excess water from the hot water cylinder (HWC) flow into the CWSC. Because any such inflow does not pass through the float operated valve, it will cause the overflow to operate, unless sufficient water is drawn from the CWSC to balance the amount coming from the vent.
3c. In very rare circumstances if there is a fault in the HWC, which allows water to backfill into the CWSC.
4. The F&E can overflow:
4a. The float valve which cuts off the incoming cold mains water to the F&E fails. This would be a continuous overflow when the mains is on.
4b. The boiler overheats. There is normally a pipe over the top of the F&E in an inverted "J" shape, called a vent pipe This is a safety device which lets excess water from the boiler flow into the F&E. Because any such inflow does not pass through the float operated valve, it will cause the overflow to operate, unless sufficient water is drawn from the F&E to balance the amount coming from the vent. Such a fault is often caused by blockage in the boiler's primary water circulation circuit
4c. The pump which circulates the water from the boiler to the hot water and central heating circuits causes the system to "pump over" into the F&E vent. This is most often caused by the same problem as 4b.
5. The WC overflow operates if there is a problem with the float operated valve in the WC cistern. This will nearly always be a constant overflow except while the cistern is refilling after being flushed.
6. Removing the CWSC and HWC could be done, but is not just a question of capping a couple of pipes.
7. You need to get someone to identify and fix the problems you have, particularly the latest "through the ceiling" leak, which suggests either a very significant leakage problem or one or more blocked overflow pipes.
Thanks so much for your detailed reply. Thats actually very helpful in terms of my understanding of the possible issues/ causes of the leak. Albeit some of it a little over my head. I can look into a couple of them but will obviously call another plumber. One question - if the issue is in the cold water tank or cylinder and I get the cold water tank and cylinder removed in advance of a new central heating system going in ( as I'd hope they would be removed anyway when getting a combi system ) are there any implications for removing them sooner?
 

Timmy D

Gas Engineer
Subscriber
Messages
323
One more to add. Had one last week where the kitchen tap was allowing mains cold to pass into the low pressure hot side and back to the tank.

Go under your kitchen sink and listen for water running in the pipes with the tap off.
 
Messages
3
One more to add. Had one last week where the kitchen tap was allowing mains cold to pass into the low pressure hot side and back to the tank.

Go under your kitchen sink and listen for water running in the pipes with the tap off.
great thanks- will try that !
 

helpsy

Plumber
Gas Engineer
Messages
1,744
One more to add. Had one last week where the kitchen tap was allowing mains cold to pass into the low pressure hot side and back to the tank.

Go under your kitchen sink and listen for water running in the pipes with the tap off.
If the tap has isolation valves, you could try turning them off and see what happens. How about a hole in the coil(depending on what levels the cisterns are on)?
 

Gasmk1

Gas Engineer
Messages
1,817
One more that can happen the heating coil in your cylinder can leak into the hot water and back fill this way.
 

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