Cold Water Tank (again)

[andyjc]

I posted a question re the overflow on my cold water tank on 14.12.05. I followed the advice given but my cold water tank still overflows. The valve is new and I've bent the float arm downwards near the float end so that the float stops the water about on the water mark line. I've put the system under load and watched the water fill the tank to the water level mark. After a couple of days though, there is water dripping from the overflow pipe. In the water tank there a what look like copper deposits. What else can I do to stop water dripping from the overflow?.

[stanleyman]

If you are happy the new valve is not leaking then the water must be coming from elsewhere. Either the system has been installed wrongly or the copper deposits might indicate a leaking heating coil in the hotwater cylinder. The central heating header tank would need to be higher than the main tank to do this. It could also be the cylinder overheating and forcing water up the air vent to the tank.

Do you have an old Primatic hot water tank where there is no other header tank for the central heating? You need to eliminate all the above possibilities.

[stanleyman]

Is the main tank actually overflowing or could the water be coming from another tank like the central heating expansion tank. If the ball is too high up they can overflow when the heating water expands and refill when cold.

[Mickeymouse]

This happened to me a short while ago and it was the coil in the main hot water tank, we did eliminate the arm in the cold water tank and also that the header tank for the central heating was causing the problem first.

[qapmoc]

Make sure that the water ball valve you have fitted in the roof tank is a high pressure one for main water and not a low pressure one such as would be fitted on a toilet tank.

[pilotlight]

andyjc, Suggest you answer the following, to eliminate queries re- your system : -- 1. Do you have one, or two tanks ? ( discounting your hot water cylinder ). 2. If you have two, one will be smaller than the other, which tank is the water overflowing from ?. 3. Have you recently had any plumbing / heating work carried out ?

[apb1979]

Do you have any mixer taps or mixer shower, it could be that the cold water is passing back up the hot when the tap is in use, as i've encountered this problem a few times before. If this is the problem, then a process of elimination is required to find out which tap it actually is.