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CWC overflow

View the thread, titled "CWC overflow" which is posted in UK Plumbers Forums on UK Plumbers Forums.

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LUCIALIA

LUCIALIA

Plumbers Arms member
Plumber
I'm currently working on a CWC that keeps overflowing every 2/3 days after i've drained it a little. I have changed the float valve & am certain it is not that, i have isolated the only mixer tap in the property & it isn't that. The HW & CH are not on as the house is currently empty. Any ideas what it could be, the vent pipe overflow from the HW cylinder does appear wet......
 
Is the central heating CF&E tank higher than the CWS tank, if so could possibly be the coil split in the cylinder.
 
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If the place is empty i would make a note of the water level in CWS tank, isolate cold feed to it & check again in a few days.
 
If it still rises after isolating the cold mains, the heating & hot water are turned off & the CWS tank is the highest point in the system........then i don't have a clue!
 
as it happens, when i left today i did isolate the cold feed to the CWS, but like you if the water level rises then i'm at a loss, hence my post on here
 
To be honest, there's not alot it can be apart from what has already been said. It cant be pumping over if the heating/water is off. If the tanks are on the same level & the CWS level is higher than the CF&E then it cant be the coil. Only leaves the ball valve at this point. Did you renew the float too, if so maybe worth just whipping the float off to check its not filled with water, this isn't uncommon!
 
Still check it, ive had new ones with a hole in before! If the water level has not risen with the water off, its obviously the ballvalve, split the valve & let a bit of water into the tank without the valve on, only a quick blast just in case any crap is in the pipe & collecting in the seating.
 
i'm confused though as i have witnessed the valve shutting off perfectly fine at least twice everytime i've emptied the CWS slightly, approx 3 times now....surely if the float was filled with water it would simply fail to shut off?
 
It may appear to be shutting of when your there, but water pressure rises overnight when there isn't as great a demand of people using water as there is during the day, therefore it could be dripping into the tank all night! As said, check the seating for crap & also check the orifice, these are not always a smooth a finish as they should be or a slight chip in it will be enough!
 
you said you have isolated the mixer taps what about the shower do you have a mixer shower
 
New float valve isolated monday text from customer today, CWC overflow dripping again. HW & CH not been used as switched off......
 
Sounds like it can only be the coil, but what is puzzling is that you say the CWS tank & CF&E tank are on the same level, therefore the CF&E water level will be lower than the level in the CWS tank, it cant be possible for the CWS tank level to raise above the CF&E level?
Dont worry about the colour of the water, not enough water is passing into the domestic side to cause discolouration, plus not all heating water is black!
 
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just to put it out there - have u shut the gate valve to the hot water( assuming vented system) , if not water could be heating to hot ( dodgy thermostat not cutting out our temp set too high) going up the vent pouring into the tank, in conjuction with dodgy fov ( mentioned in early post) for dripping overnight - i know not likely as overflow would accomadate but u never know

as i say just a random theory to put it out there
 
When you isolated the cold feed to the CWS tank, did you do this from the main incoming stop tap or is there a seperate one for the tank? Will be best to use the main incoming stop tap & leave an outside tap open! I'm clutching at straws but possible the stop tap is passing! Can you get some pics of the roof tanks!
If it was the coil, the water would be coming out of the CF&E tank overflow!!
 
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I'm going back round tomorrow, I'll take some pics. I was going to fit an iso valve before the float valve in case the stop tap for the CWs is letting by
 
2011-03-21 15.53.15.jpg2011-03-21 15.53.20.jpg2011-03-21 15.53.38.jpg2011-03-21 15.53.49.jpg2011-03-21 15.53.28.jpgOK, I've been back round, overflowing again I am certain the new float valve is fine as is the stop tap, i have noticed however that the vent pipe is damp.....curious as the HW & CH is & has been switched off!? Apologies for the poor qualities of the pics,taken on my mobile as i forgot my camera
pencil.png
 
I cant work this one out...If there is no heating or hot water on it cant be expanding or pumping over, if the cold mains is off then where is the water coming from! It cant be the coil because the CF&E is lower so it would be overflowing from there! Got me foxed!
 
Im guessing he's using it to syphon some water out...could of just opened a hot tap. Either that or we sussed you out....lol
 
I was draining some water off. A friend of mine has suggested that the vent pipe is to low, so I shall be raising it up a few inches in the next few days.
 
Just been contacted by customer, water is now coming out of overflow quite fast & after not even 24 hrs & the Cwc & cylinder were drained?!
 

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LUCIALIA,
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PlumbBobBob,
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