How to test for a split coil.

[MickBrown]

I changed a ballcock in a combination thermal store as the expansion tank was full and overflowing. I lowered the water level in the expansion tank to something more suitable. The ballcock was fine, no leaks. Two days later the expansion tank is overflowing again and I suspect it may be a split hot water coil. Is there anyway to test it whilst the cylinder is in situ? Haven't been back yet just getting ideas before I do. the customer said the overflow was passing about 30 litres per day.

 

[diamondgas]

You could isolate the ball valve supply to the expansion tank. If the water level continues to rise and overflow then it has to be coming from within! Alternatively if the custard is on a water meter check to see if it's moving with everything off then isolate cold to thermal store and see if it stops moving

 

[Barry98]

drain cylinder and get a torch in if needs must ? why do you think its split ? dirty water etc ?

 

[stevetheplumber]

disconnect the coil and use a pressure test kit?

 

[Dotty]

disconnect the coil and use a pressure test kit?

If It's split, and you've the coil disconnected, you'd know fairly soon because you'd run out of towels!

 

[petercj]

The best way is to put a ferret in the bottom of the coil and if he comes out soaking wet at the top you know the coil's buggered.

 

[PETE 123]

Are you sure its not cold main crossing over to hot somewhere and going up to tank

 

[stevetheplumber]

Are you sure its not cold main crossing over to hot somewhere and going up to tank

its a thermal store both hot and cold would be at mains pressure so no tank header tank only feeds the heating and the store

 

[stevetheplumber]

If It's split, and you've the coil disconnected, you'd know fairly soon because you'd run out of towels!

the coil is under mains pressure from within and only low header tank pressure on the outside, its quite possible for the water to only pass one way from high to low pressure once again its a thermal store with a mains fed coil through it

 

[Dotty]

Lol I missed that one!

 

[MickBrown]

Thanks for all the replies. As I haven't been back yet all I know is the expansion tank is filling with water and overflowing, I changed the ballcock on Wednesday and lowered the expansion tank water level. The customer telephoned me Friday morning saying it had started to overflow again. I have to make further checks but I am assuming that if the water is not coming out the ballcock then it must be coming from the main cylinder and the only source would be the mains coil. I did notice that the water in the expansion tank was quite hot, with hindsight probably hotter than I would have expected if the overflow was caused by the ballcock. So it seems reasonable to assume the water is coming from the main cylinder which is hot water.
I will try isolating the ballcock and see if the water keeps overflowing. Another thing I thought of is, if I turn off the main stopcock and drain the taps downstairs, if there is a split then the water from the hot cylinder may flow back through the split and come out of the cold tap downstairs. As the split is obviously small as the amount of water overflowing is not great (about 30 litres a day) then although mains pressure may force the water out of the coil gravity hot water may not be forced into the coil, but I can try.

 

[stevetheplumber]

ive got a thermal store with the header tank just above and that get pretty warm

 

[buckley plumb]

Are you sure its not cold main crossing over to hot somewhere and going up to tank

now thats a thought for a normal tank and cyl system . i wonder how many cylinders have been changed do to this and still do the same.i have to admit i changed a cyl years ago and it still overflowed to find it was the shower valve .

ant

 

[MickBrown]

This is a thermal store, so just a tank full of water with a header tank. There is the primary heating coil and a secondary hot water coil. I turned off the mains to the ballcock and the overflow still occurred. The primary heating circuit is a pressurised system and there is no loss of pressure so the split cannot be in that coil. I have asked the customer to turn off the cold supply to the hot coil overnight or when they are out all day, if the overflow stops then that will confirm there is a split in the hot water coil. These cylinders cost over a thousand pounds so need to be 100% certain before changing it.

 

[buckley plumb]

This is a thermal store, so just a tank full of water with a header tank. There is the primary heating coil and a secondary hot water coil. I turned off the mains to the ballcock and the overflow still occurred. The primary heating circuit is a pressurised system and there is no loss of pressure so the split cannot be in that coil. I have asked the customer to turn off the cold supply to the hot coil overnight or when they are out all day, if the overflow stops then that will confirm there is a split in the hot water coil. These cylinders cost over a thousand pounds so need to be 100% certain before changing it.

you could fit a check valve on the hw out pipe to eliminate the hot cold mixing possibility . i know you say its mains hot but some have pressure reducers on the cold to the cylinder. and as others say service valve on supply

ant

 

[phpaul]

only 100 for a shower cart try that first