Cold water tank in the attic overflowing

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Cold water tank in the attic overflowing

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GGg

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Hi All,

Looking for some advice. The tank in the attic has been trickling out of the overflow for a few weeks now.

I have an open vented system with a hot water pump (Stuart Turner monsoon twin 3) fitted.

Have already changed the valve and float in the attic. Set it very low but water is above the float. Tested it fine know it shuts off the feed that way.

Also changed the thermostat on hot water cylinder, so tank isn’t getting too hot and venting over.

I do have a shower fitted with mains cold and tank fed hot. (Plumber at the time said it would be fine because hot water is pumped) as well as 3 other mixers in the house with same hot/cold set up.

Looking online could it be the hot water is being overpowered by the cold, with mains then backfilling down the hot water pipe and filling the attic? I can see this can be resolved with a non return valve? And instead of fitting 4 non return valves can I fit one 22mm NRV on the flow from the pump? (Not the feed as this stops any ability to vent)

Thanks and sorry for the long winded post.
 
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Positive head or neg head pump ?
 
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GGg said:
Hi All,

Looking for some advice. The tank in the attic has been trickling out of the overflow for a few weeks now.

I have an open vented system with a hot water pump (Stuart Turner monsoon twin 3) fitted.

Have already changed the valve and float in the attic. Set it very low but water is above the float. Tested it fine know it shuts off the feed that way.

Also changed the thermostat on hot water cylinder, so tank isn’t getting too hot and venting over.

I do have a shower fitted with mains cold and tank fed hot. (Plumber at the time said it would be fine because hot water is pumped) as well as 3 other mixers in the house with same hot/cold set up.

Looking online could it be the hot water is being overpowered by the cold, with mains then backfilling down the hot water pipe and filling the attic? I can see this can be resolved with a non return valve? And instead of fitting 4 non return valves can I fit one 22mm NRV on the flow from the pump? (Not the feed as this stops any ability to vent)

Thanks and sorry for the long winded post.
Click to expand...

It can be yes, a customer had a tap fitted and another plumber had changed the float valve twice. Turned out it was backfilling the cwsc (cold tank) and overflowing. I advised he fit check valves or change the tap.
 
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CBW1982 said:
It can be yes, a customer had a tap fitted and another plumber had changed the float valve twice. Turned out it was backfilling the cwsc (cold tank) and overflowing. I advised he fit check valves or change the tap.
Click to expand...

If you want to check this then try and put your hand in the tank and feel where the cold feeds the cylinder
 
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That’s what I just said?? If the f&e is higher than the cwsc then if the coil is split then the water levels in the two tanks will try and level out
 
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So. Sat in the attic whilst the mixer taps where tested. Felt the feed at the bottom of the cw tank and it was sucking the water out quite powerfully, nothing being pressed back up?

The valve has now settled and the water is the correct level.

But in a day or so it will be overflowing again. I’m completely baffled. Picture of the F&E tank just in case I’m missing something obvious.

EA084DBB-C5D5-4C3D-BA80-228951815680.jpeg
 
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Think it’s the coil. Can see water going onto the CWSC when the hot water is turned on to heat up. (Nothing to do with mixer) tried to show a video but it won’t upload. Is that what would happen? The feed pipe down to the bottom of the tank is also getting warm.
 
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GGg said:
Think it’s the coil. Can see water going onto the CWSC when the hot water is turned on to heat up. (Nothing to do with mixer) tried to show a video but it won’t upload. Is that what would happen? The feed pipe down to the bottom of the tank is also getting warm.
Click to expand...
Potentially but keep in mind that that pipe will also deal with expansion so it is likely to be warm
 
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If you sit up there long enough the smaller f&e tank should start to fill if the water level is indeed higher the other alternative is to shut off the pipes to the pump so there’s no way that water can be coming from anywhere else
 
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The small tank will fill your central heating the big tank fills your cylinder. Assuming it’s piped correctly the only place these to waters come close is in the coil in the cylinder, central heating water inside, domestic hot water outside. There could be a small pinhole in your coil meaning that when it heats and expands water from the smaller tank is able to pass into the domestic hot water. This then effectively makes it all one circuit no longer separate so the two tanks in the loft will try and achieve the same water level. This will only be the case though if the water level in the smaller tank is higher than that in the larger tank otherwise the same would happen only in reverse
 
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