UK Plumber Forum

[RPM]

This comes up from time to time so just how many possible reasons for a cold water tank in the loft to overflow are there?

(One answer per member please rather than one member listing all the answers will hopefully keep this thread going longer).

[Best]

Okay, I am going to start it of with, - Faulty mixer tap allowing mains higher pressure water to go into hot pipework to hot cylinder and up the cylinder feed into bottom of cold water tank.
On a quick count I say 11 possibilities at least

[Last Plumber]

Hole in an indirect Cylinders coil on an open vented hot water system, where the open vented Heating F&E tank has a higher water level than the cold water storage tank that feeds the Cylinder.

Sorry to make that long winded

[REDSAW]

punctured ball float that has filled with water, failing to lift and close of the inlet valve.

[Keefy]

Split diaphram washer on the inlet.

[RPM]

The ball being covered in crud weighing it down stopping it from rising.

[Croppie]

Dirt in the seat preventing it resealing.

[REDSAW]

Dirt in the seat preventing it resealing.

i get that problem sometimes

[jonnyswamp]

Faulty washer, not the inlet washer, the fibre one that sits between the two mating faces of the valve body and the thread body
Admittedly I've only seen it a few times

[Mr KJ]

Failed stat allowing cylinder to overheat and "pump over" the expanded volume into the cwsc

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[Porkchop]

Half decomposed rat still clutching to the brass arm since that time months ago when he kicked his last little kick in an attempt to get out. (he's weighing the ball valve down)

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[jack]

Dirt in the seat preventing it resealing.

Many time found this problem, but not solved.

[joni os]

Thermostatic mixer valve with a mains pressure cold feed. Difficult to identify when there are 50+ in a commercial building and you've been assured all are on a gravity cold feed. Never trust a maintenance man.