Puma 100e: Water leaking form the automatic air vent!!!

21 Nov 2006
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United Kingdom
After replacing the DHW flow switch yesterday, I find myself waking up to a leaking auto air vent. Water has been leaking out of the vent down onto the floor.

After attempting to drain the system by shutting off the isolation valves and running the hot water taps. The air vent continued to leak.

Went in for a closer look to notice that there was a small black screw cap that had been removed from the air vent . I have replace that which has now stopped the leak. Could the solution have been that simple or is this just a temporary fix. Can't understand why this cap had beeen removed in the first place unless the guy I had round to service the boiler did so back in December.

Any suggestions would be much appreciated!
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At first yes. But after glancing at the service manual I loosened it. the leak has now resumed.
Before replacing the DHW flow switch I was running the washining machine which was drawing HW from the system. As a result the CH had become so hot, despite not actually being on, that I decided to shut off all the radiators in the flat.
This caused an overflow in the system and I believe that this might have something to do with the airvent situation.
The water leaking from the air vent is warm/hot.
should be a kind of diaphragm in there to let air out but not water. sounds like this is passing,I'd replace it
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Is it possible to stop the leak or cut of the water supply until I can get someone to replace.

I have cut off the supply from the isolation valves and tried to drain the system as I had before when i replaced the DHW flowswitch. But it continues to leak water.

This boiler is a complete nightmare!
Could be water inalready in your expantion vessel .if you screw the black plastic nut fully it should stop it until its replaced
Thanks I'll order the part now and give it go tomorrow but am concerned that when I remove the auto air vent the pipe its sits on will start to spill out loads of water.
This boiler is a complete nightmare!

I would say that the owner is causing most of these nightmares. Like everything else in the world you should not rush into something you dont understand.

You should never have touched the isolation valves. That would not have achieved anything apart from causing them to leak.

To replace the AAV the system has to be drained from a drain cock or a rad bleed screw.

Until you are ready to do than just screw the cap closed.

Unfortuantely I am not near the boiler at the moment. But did give it a quick glance this morning and both guages were within the limits.
Would the pressure relief valve be able to have and afftec on the leak.?
Thanks Tony,

I agree, although I hate to be defeated and shall take one final crack as I'm pretty sure where I have been going wrong. Failling that I think it is indeed time to call in the experts.


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