"Andy Champ" wrote in message
...
I have a standard gas boiler heating the hot water and radiators. The hot
water cylinder has an indirect coil.

There's a cold water tank and a seperate header tank for the rads/coil in
the loft. The base of the two tanks is level, so the water in the header
tank is a couple of feet below the main tank.

I've been suffering problems with the overflow from the header tank
dripping. So I changed the rubber washer. Then the fibre washer. Then I
turned off the stop cock. Now I've actually disconnected the feed into
the ball valve from the tank - and *STILL* it drips. The only thing I can
think of left that could be causing the problem is a leak in the coil in
the cylinder. Before I go out and spend 200 squid on a new tank and spend
a weekend pulling the darn thing apart, is there anything easier/cheaper
that could be causing it?

Is there a way of isolating the coil? Leave CH off so zone valve is closed
and close up a lockshield gate valve on the coil return (if one there). Even
though the gate valve may be closed it may pass water.

You have fully isolated the cold water into the F&E tank. The symptoms are
that of a leaking coil.

As you are having some major work, you may want to improve the system.
Replace the cylinder with a heat bank sylinder (thermal store) giving mains
water pressure at all the taps and showers. It does away with the two tanks
in the loft. The heat bank could go in the loft out of the way where the old
cold water tank was, liberating space in the house. The system would be
vastly improved and well worth doing.