Hi All
I've got a 25 year old Potterton gas boiler. Open vented, Y-plan arrangement. Close to the boiler, on one of the vertical water pipes, there is a little valve. I assume it's a pressure relief valve. Over the last month or so, it has started to weep. Just a drop or two every week or so. Does this indicate a problem that is more severe than just a failing relief valve, and if so, what tests can be made?
A picture would be useful to decide what it is.
If it is a relief valve then it may be a simple spring and piston thing that can be dismantled and examined.
It's very unlikely to be a pressure relief valve - 'cos there's no pressure to speak of in an open vented system. More likely to be an automatic air bleed valve or somesuch. A picture would be useful!
Ta. OK. I'll post a picture (somewhere) tonight.
Is it at the end of a pipe? If so, sounds like what's called an 'air bottle' - an automatic vent. There are different types, but some have a manual valve on the top to seal them after they've done what's needed at initial fill. Check that is tight.
Ta. No, it's inline. I'll post a piccy.
By popular demand;
Is that a spring visible in the end? It's not any of the normal (modern) automatic air vent valves but that doesn't mean it isn't one. Seems a bit daft to have in on a T in a vertical pipe for an air vent but then plumbers are not the brightest of people at time...
What happens if you gently and slowly unscrew the cap? Have some old towels underneath, the chances are this is in the primary and the water in there is most likely black and stains anything. If it is an air vent I suspect a small bit of crud has got into the seat and is keeping it just a tiny bit open.
It looks like a spring.
What is an air vent valve used for? Is it supposed to automatically remove trapped air?
Hmm. I bet if I started to unscrew it nothing would happen, then, whoosh, all my lovely dirty hot water flooding my kitchen.
If it's not a safety issue, then my feeling is to leave it alone. Thanks BTW.
I do have a manual bleed screw at the top of a vert piece of pipe. I open this from time to time, never very much air, and the water looks clean (well, I guess it would do at the top of the circuit).
Thanks.
On Wed, 13 Dec 2006 09:53:55 -0000 someone who may be "Grumps" wrote this:-
To vent air from the system.
If it is an automatic air vent. However, these sometimes stop working.
A manual air vent needs to be operated from time to time. However, not everyone knows or cares why they are fitted.
This gadget looks like an air vent, probably automatic, but it is fitted in the wrong place. It should be at the top of a vertical piece of pipe, called an air bottle, in which the air gathers before release.
Yes - although that doesn't look like one. They usually have a float operating the valve - the principle being that only water will close it.
It's an early version of a pressure relief valve. They are usually fitted if the vent pipe from the boiler does not continually rise.
You will need to drain the system to repair it, when I tried to repair one I was not been successful and had to replace it.
If you can live with a very small leak that might be the best solution as the heating system is probably up for a major overhaul soon anyway.
Thanks. I thought it might've been.
Well, it has got some horizontal sections.
System was drained in the spring. Quite clean water, but I'm sure there's a lot more sludge in there.
Indeed. I think I'll leave it for now. Ta.
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