Pressure drop in boiler

29 Nov 2007
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United Kingdom
I have just installed another radiator to my worcester 24cdi central heating system to which when I opened the isolation valve to let water in the pressure in the water system dropped, I then put the key in the boiler and turned the water pressure up to 1.5bar, after removing the key the pressure has droped to 0 in about a hour, I have noticed that the 15ml copper overflow pipe outside by the boiler has got water coming from it.Could anyone tell me if they know what the problem could be and what I could do please.

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Read FAQ's on expansion vessels and then replace clean safety valve.
Read FAQ's on expansion vessels and then replace clean safety valve.

Thanks for the reply, I will try to drain the system and pressurize the expansion tank to 0.7, I just done a quick check and air is coming out of the tank, so hopefully the tank is ok.

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No particular reason to suspect an Expansion Vessel (EV) fault. Just try cleaning the PRV (safety valve) so that it doesn't drip. Turning the red knob to rapidly open and close it a few times is sometimes sufficient to get it seating properly.

When you've dealt with the PRV you can check the function of the EV by observing the extent of the pressure rise and fall as the system heats and cools. If the pressure change is 0.5 bar is less the EV is OK. If it's 1.0 bar or more then it may need attention.

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