Leaking 'valve' above boiler

Hi guys
I've woken up the last few mornings to find a small pool of brownish water under our boiler. Finally got round to taking the boiler cover off and it appears to be coming from some sort of valve/connector on the pipework that runs from the top of the boiler. No idea what the 'valve' does but rather than try to explain it, I've posted a few pics here
http://www.jimm.dsl.pipex.com /
The water is a slow drip from the central hole, and I think that whilst the boiler is running it is evaporating the drip before it has time to run down to the bottom and hence it doesn't materalise during the day.
The pipework is about 30 years old (as is the boiler) but I hope to re-fit the kitchen early next year. Rather than hack the pipework to pieces now do you think I can get away with sealing the hole (plumbers mait ?) for 6 months or so.
Thanks
Jim
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It looks like a water pressure safety valve that was stipulated by regulations to be fitted to boilers in the flow pipework as close as possible to the boiler as possible. There is one on my system (about 20 years old). It is a spring loaded valve which releases water pressure if there is a serious failure. They are not specified now (maybe because boilers have electronic safeguards). It may just be leaking - but as the system is old, it may be actually operating because the system is getting blocked by sludge. If you decide to seal it then check the system overflow and cold water feed pipes are not blocked and there is water in the expansion tank. Also check that the boiler thermostat is still working ok and all other thermostats and valves are working etc.
Dave
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Its a spring loaded safety pressure relief valve. They were commonly fitted even on vented systems as a protection against the pipes from the boiler freezing and the boiler then firing up and bursting. Mostly for indoor mounted boilers they were superfluous and for modern boilers where there is a likelihood of freezing a frost protection stat is provided. There has probably been some corrosion which has led to weepage starting. Check your feed and vent pipes are clear then it is possible to tighten the collar down a little against the spring which will serve as a short term fix. Do check the feed and vent first though.

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Plumbers mait won't stop it. You could simply go out and buy a new screw in safety valve, drain off , swap the valve, refill and carry on. The valve will only cost a few quid
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Thanks for the input guys, I've checked the inlet/overflow which both appeared to be free and I've managed to 'plug' the valve with a plastic stopper and a smear of mait. Hopefully this will hold until I can make a proper repair.
Jim

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