HELP! - DRIPPING OVERFLOW FROM COLD WATER TANK

Help Anyone!
My Coldwater tank in the loft (a Polytank) is dripping from the overflow.
I have assumed it was a leaking float valve and replaced it yesterday. I have also set the float to it's lowest position, to try and get the water level down a bit.
To my dismay it is dripping again! There is one other pipe which feeds into the top (I think it is from the hot water tank?) but as far as I can see there is no water coming through. If there was, what would the cause be?
Could I have been unlucky and bought a second faulty float valve?
I would be grateful for anyone's thoughts as there seems to be no logic to this!
Thanks in anticipation,
Andy
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Check that the incoming cold water pipe is supported properly, if this is sagging, its weight could raise the float, causing the problem.
--
Gavin Gillespie
Giltbrook
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I suffered the same symptoms with a system that turned out to be a split in the heat exchanger coil inside the Hot Water cyclinder. This was allowing the indirectly heated hot water system to feed in to the primary heating system thereby adding water to it which ended up in the header tank. To check for this, iscolate the feed to your header tank and see if it fills up, it may take a day or so to notice the difference. Cure inthis case is new hot water cylinder I'm afraid :o(
Bert
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Be aware that condensation can cause overflow and other pipes to drip. If you have e.g. hot water getting into teh tank, it will cause hugh humidity in teh space above teh water, and if the outside air temp is low, condesnsation will form and drip out.
The key thing to check is if the water level is up to the overflow pipe or not, if not its condensation. Otherwise something is (over)filling the tank...
Gavin Gillespie wrote:

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The only things to cause water to come out of the over flow are the tank filling up too much, or a faulty ballvalve.
I would say your replacement ballvalve is faulty.
Check the washer seating, adjust the fill height or replace it
dg

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Some ideas:
1. Did you replace the actual ball? If not, is the old one leaky and so not floating properly? (Been there, done that one!)
2. Does the water shut right off when the ball is floating? Even a slow trickle or drip can cause the tank to overflow in time.
3. Overflow from HW system- is there a pattern. Does it leak after the HW has been heating?
4. If the CH header tank is higher than the main tank, you could have a leak in the heat exchanger coil in the HW tank. (This doesn't apply of the CH header tank is lower.)
5. Is the overflow from the CH header tank routed to drain into the main tank (very naughty but seen it done).
6. Hole in the roof letting rain in. (seen it happen with a tank with no cover!)
--
73
Brian
G8OSN
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In the past I've had problems when there has been work done on the mains and grit has got onto the seal preventing the valve from fully closing.
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Alan
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Guys,
Thanks so much for the responses - you have given me several new things to try. Fingers crossed it's not the Hot Water tank gone!
Thanks again
Andy
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Hello Andy

The other pipe is probably the vent/overflow. Test it by taping a single sheet of bogroll over the end - if it breaks while you're away, then water's coming out. Fix /that/ by turning down the CH pump.

It's possible, or the fitting was wrong, or that the pressure is too high and you've not fitted the twirly reducer valve, or that the mount is insufficient and the water's pushing the wall out at the fixing, or that you've simply not adjusted it Ok.
Is the ballvalve dripping? Empty the tank enough to start a normal fill sequence and watch and wait.
If the pressure is very high, get a bigger ballvalve. I tried about half a dozen different valves for a field trough where the pressure overnight soared to stupid levels (sometimes bursting joints). Only by fitting a larger sized ball and valve (designed for a high capacity tank, the ball was three times the size of a standard one). You might get away with just a bigger ball to counteract the pressure forcing it back down.
--
Simon Avery, Dartmoor, UK
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