Hi all before christmas I noticed water dripping from my overflow so up in the loft I went and sure enough the float was under the water the cylinder was very old a plumber friend said it could be the central heating coil leaking and filling the tank so I fitted a new tank and a part2 float valve. 2 days later the same thing happens water from the overflow so basically all new stuff and fittings same problem its an Ideal mexico 2 boiler very old but brilliant. the old tank has never had a tank stat so I didn't fit 1 the hot water is back filling into the cold tank that directly above the cylinder with the central heating tank between them. The tank is an indirect and vented. thanks in advance.