Dripping CH overflow

[Tricky Dicky]

I have recently noticed my expansion tank overflow is dripping, it only seems to have started during this protracted cold spell. I have inspected the tank and it is not the ball c*ck the excess water is coming from the expansion pipe. I have drained some water from the system to reduce the water level, vented all the radiators but found no air in the system, I have also set the pump on a lower setting. Is this something I should be concerned about or is it the system doing what it should be doing. If it requires attention what needs doing?

Thanks Richard

[Roger Mills]

Does the level continue to rise when you drain some out and tie up the ball valve to stop any fresh mains water from coming in?

Do you have a header tank for the hot water system, whose level is higher than that in the F&E tank?

If the answer to both of these questions is 'yes', the prime suspect - as someone else has suggested - has to be a hole in the indirect coil inside the HW cylinder. The pressure in the cylinder - surrounding the coil - will be slightly higher than that inside the coil due to the difference in levels of the water in the respective header tanks. Thus, if there is a leak in the coil, water will flow *into* the coil, and thus into the primary circuit, causing the water level in the F&E tank to rise.

[John]

Can it be:

When the water cools it contracts and lowers the level in the header tank. This admits more water - then when it heats up it expands and pushes the surplus out of the overflow. I think this line is worth thinking about before looking for leaks in the heat exchanger. If the header tank is a relatively small surface area then a bit of expansion can make quite a difference to the level.

Does it mainly leak when starting up the heating and then doesn't leak until next time? The header tank acts as an expansion space.

[Roger Mills]

That *can* happen if the water level is set too high to start with.

But if, with the static level lowered and the ball valve disabled, the level *still* rises (other than by the natural effects of expansion) there *must* be some 'foreign' water getting into the primary ciruit.

[Tricky Dicky]

Thanks all I will be trying to make sure it is not the ball c*ck today. I will report back later.

Richard

[Tricky Dicky]

Back again

I have checked the ball c*ck on the F&E tank, the washer was slightly worn changed it but still got an ever so slight drip. I changed it with a new one ( belt & braces) no drips from the ball c*ck but all the time I was working on the ball c*ck the heating was on and water continued to drip out of the expansion pipe. Conclusion - it must be the heat exchanger in the hot water cistern. Only good thing is at least this is an item covered under EONs central heating care so it should be a free repair/replacement.

Thanks for all the help Richard