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]

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)

 

[GGg]

Turned mains water back and and immediately started going back up into the tank. I can’t access shower mixer to isolate but assumed isolating the entire feed off the hot water pump would do it.

 

[Riley]

So it literally feeds the pump?

 

[Riley]

Sorry I’m getting mixed messages with this does the pump do hot and cold water for the whole house or just for one shower. If all the house is pumped then the fault can only be with your kitchen mixer

 

[GGg]

Sorry I’m getting mixed messages with this does the pump do hot and cold water for the whole house or just for one shower

Pump does whole house, hence I thought if I used the isolation valves on the pump it would stop any backfilling mains. But either the isolation valves aren’t turning off fully or im barking up the wrong tree. However I can feel the pipes on the pump they are cold as if mains water is flowing through.

 

[Riley]

Kitchen mixer won’t be pumped

 

[GGg]

Kitchen mixer won’t be pumped

Kitchen mixer is pumped, turns pump on etc.

 

[Riley]

Only on hot, the cold should be straight from the mains

 

[GGg]

Only on hot, the cold should be straight from the mains

Yes. 3 taps and shower are all like that.

 

[GGg]

Only the bath is tank fed hot and cold.

 

[Riley]

Right let’s backtrack as we keep going round in circles here. Any outlet you have that is hot pumped and cold mains could be your culprit and from what you said sounds the only logical explanation

 

[GGg]

Yep agreed. I’m just going to put a NRV on the outlet from the pump for the sake of £5 and my brain exploding. Will update after fitted.

 

[Riley]

Surely you can just isolate the pump on one of the flexible hoses

 

[GGg]

Surely you can just isolate the pump on one of the flexible hoses

Tried that. But either the isolating valves aren’t closing fully or I’m on the wrong track.

 

[GGg]

Ok so NRV fitted. Isn’t coming back into the tank at the moment but maybe because I turned off. Will check it over the course of the day to see if it’s come back. Thanks again for your help will keep you posted.

 

[GGg]

Ok so NRV fitted. Isn’t coming back into the tank at the moment but maybe because I turned everything off to fit the NRV. Will check it over the course of the day to see if it’s come back. Thanks again for your help will keep you posted.

View attachment 37114

 

[Riley]

I’d still look at fixing the issue as all you’ve done is mask it.

 

[Rob876]

Yes they can

So, true mixer taps with different supplied water pressures can create backflow when the taps are off? Within the body of the mixer tap?

 

[GGg]

So, true mixer taps with different supplied water pressures can create backflow when the taps are off? Within the body of the mixer tap?

My issue was the shower mixer rather than the taps. But was flowing through when off

 

[helon]

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

Have traditional vented indirect system, in my case F&E tank base same level as large tank, so top level below, F&E tank overflows/steady trickle, maybe one bucket every 3 hours, also somewhat brownish water (water from taps crystal clear), guess it is coil, or could system be too hot (at one stage hot water was VERY hot), any suggestion?