Dripping overflow when mains water is off?

26 Mar 2012
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United Kingdom
Hi there,

We have just purchased a property and we a not currently occupying it. We have noticed that when we leave the house we turn the power off and the mains water supply, but an overflow pipe starts to drip. It appears to come from the toilet or combi boiler area of the house.

We flush the toilet so it's empty, does anyone know why it starts dripping when the water is turned off.

Thanks for your time
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Although you have a combination boiler the toilet still could be fed by a tank in the loft. If you have turned the mains off then check to see if the cistern is still filling up. If so then either the main has not been fully turned off or the toilet is fed from a tank. Check. Either way the ball valve washer in the toilet needs to be changed. :D
Thank you for your reply.

I have checked and the cistern doesn't fill up after the water has been turned off and there is no header tank in the loft space.
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In that case it could possibly be the 'Pressure Relief Valve' on the boiler, which is letting by. May be worth having it checked out. It could just be the valve or another fault wihch is activating the PRV.

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