If this leak is very recent then the ball valve needs a new washer as the tank is overfilling.
Overflow pipe from tank in attic.
Tested it fine know it shuts off the feed that way.
They re a vital part of your home s plumbing system.
The tank in the attic has been trickling out of the overflow for a few weeks now.
An overflow pipe leads from a water storage tank or cistern inside your home to the outside.
With this type of valve the brass stem is bent downwards carefully to adjust the water level.
Unless your pressurised hw system is in the attic too then it could be a blowoff safety valve no idea about heating system the heating is run from a stanley oil fired cooker don t think it s pressurised though.
If not then u will still have a expansion tank in the attic with an overflow.
Have already changed the valve and float in the attic.
The tank will either be your cold water header tank or the flow and expansion tank for the heating system and the valve is a type 1.
Set it very low but water is above the float.
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How to diagnose and repair a dripping overflow.
The overflow pipes from the tanks in the loft generally come out at the eaves so it unlikely to be them.
It could be that tank or it could be a toilet overflowing.
If the water in the tank or cistern fills up to a higher level than it should the excess water flows down the overflow pipe and runs outside rather than leaking into the room.
Looking for some advice.