Cold water tank in the attic overflowing

[GGg]

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.

 

[Riley]

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.

Potentially but keep in mind that that pipe will also deal with expansion so it is likely to be warm

 

[GGg]

The 22mm pipe from the bottom of the bigger cold water tank. That’s the water that’s dribbling through on the picture.

 

[Riley]

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

 

[GGg]

I’ve turned the hot water pump off. It’s still filling in the bigger tank, which I guess would then fill the smaller tank. But why/how is water going up that pipe?

 

[Riley]

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

 

[GGg]

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

Ah sorry I thought it was normal but maybe my system is different. I have 3 tanks. The two I’ve shown are hot water. There’s a smaller tank again that feeds the CH.

 

[Riley]

Yes that will be the f&e is that above the other two tanks. It’s likely a second tank was installed to cope with the pump demand

 

[GGg]

I’ll go back up tomorrow to check but I think that tank is a lot lower down. Thanks for all your responses and help. However I assume the water coming back up into the CW tank is the issue as it’s being pushed back up the feed. Will take some
More pictures tomorrow. Thanks again.

 

[Riley]

Which could be the case if the f&e water level is higher than the other two tanks. If the coil has split and the f&e is higher then the water will of course come back up the feed pipe. I mean this in the nicest way mate but I think you might need a pro in. If you find the problem I’m not sure what you intend to do

 

[GGg]

Which could be the case if the f&e water level is higher than the other two tanks. If the coil has split and the f&e is higher then the water will of course come back up the feed pipe. I mean this in the nicest way mate but I think you might need a pro in. If you find the problem I’m not sure what you intend to do

Tbh I’ve had plumbers in for the last 4 weeks, changed the two way valves, cylinder stat, ball valve etc and now stating it was my hot water pump.

So I’ve had enough of being fobbed off and wanted a decision on what was wrong so I could then understand and agree/disagree with the next plumber who comes in. If it’s the cylinder then I’ll get someone in to change it, just wanted to diagnose it correctly. As all they seem to be doing is winging it.

I appreciate your comments on getting a pro in, no offence taken I’m an accountant not a plumber.

 

[Riley]

Thank you we are happy to help but likewise we don’t want to see someone flood their house. Do you understand the science of what I was trying to explain

 

[GGg]

Thank you we are happy to help but likewise we don’t want to see someone flood their house. Do you understand the science of what I was trying to explain

Yeah I get it. If the F&E is higher than those two then it will try to level itself out. But the F&E tank is only a small 10 gallon tank so I don’t think it’s higher than that big tank. However I will check.

 

[Riley]

The water level is the key factor not the actual size of the tank

 

[GGg]

The water level is the key factor not the actual size of the tank

This is what a meant by small. It isn’t possible for the CH tank level to be higher than the other two. Woke up this morning and the tanks are full again. And the CWSC is warm with the feed pipe very hot to touch.

 

[Riley]

Ok then it’s impossible to tell from the angle of your pics the levels. That will be down to you. As long as the water in the f&e is lower than that in the larger tanks then you can rule out split coil. Only logical other fault then would be one of your mixers passing

 

[GGg]

Ok then it’s impossible to tell from the angle of your pics the levels. That will be down to you. As long as the water in the f&e is lower than that in the larger tanks then you can rule out split coil. Only logical other fault then would be one of your mixers passing

Also if the coil was split would the water in the hot water tank be dirty? As it was relatively clean.

Can the mixers pass if they are off? As this has happened overnight so nothing on.

Thanks again.

 

[Riley]

Yes they can

 

[Riley]

Not always dirty depends on the system

 

[Riley]

If you have isolators on mixer taps you will need to turn them off systematically to work out which one. My bet would be a shower

 

[GGg]

If you have isolators on mixer taps you will need to turn them off systematically to work out which one. My bet would be a shower

Yeah will go around turning off the isolators on each tap and checking to see if the flow has stopped. Hopefully find it that way.

 

[GGg]

No joy. Turned them off one by one. And then turned off the isolation valve on the entire feed on the pump. Still trickling.

 

[Riley]

Let it drop back down to below the overflow

 

[GGg]

I noticed on the hot water pipes on the pump where freezing cold. Like a mains water pipe. Not sure if this is a stupid point to make, but I turned off the mains water and the water going into the tank has now stopped. If the coil was split wouldn’t it drain down the F&E?

 

[Riley]

How many pipes come off the two larger tanks you have a cold feed to the cylinder. Anything else?

 

[GGg]

How many pipes come off the two larger tanks you have a cold feed to the cylinder. Anything else?

Cold feed to cylinder on the one tank. The other tank has a cold feed to the pump for the bath (both hot and cold tank fed)