water level rose in CH expansion tank with system off and resolved when

I've just got back from hols to find the CH expansion warning pipe dripping and algal?sp growth on the lean-to roof as a result so it had obviously been dripping for some time. The boiler had been off while we were away. I decided to leave investigating until today but magically the dripping has stopped now that the boiler has been run a few times for hot water. Why'd that happen?
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dave @ stejonda

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dave @ stejonda wrote:

The ball-cock has been exercised and the washer is sealing better?
Worse case is your pimary coil in your hw cylinder has a small leak and this is normally not noticed when you're drawing off hot water.
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Ok thanks Bill, I'll bear those in mind
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dave @ stejonda

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