Replacing an automatic air vent ????

[Nigel Heather the-heathers.co.]

The automatic air vent in my heating system is faulty - basically it leaks water and I have to keep topping up the system, but the leak is getting worse over time - possibly only some trapped dirt but I'd prefer to replace it rather than try and fix it.

It is on the heat exchanger circuit and is at the highest point and above the pump.

The pump itself has isolating valves either side, so that would be pretty easy to remove.

But there is no isolating valve between the air vent and the rest of the system.

As it is at the highest point in the system, can I just undo it and replace or is water going to start gushing out as soon as start removing it?

Basically, I'm hoping I don't have to drain the system just to replace it.

I'd appreciate any advice or guidance.

Cheers,

Nigel

[fred]

In article , Nigel Heather the-heathers.co.uk> writes

When I put one in my system I used one that had a plunger based shut off valve so that it sealed when the main body was unscrewed but these little niceties cost a little extra so it's unlikely one fitted to a boiler will be that clever. As an alternative to replacement there is usually a plastic cap on top of the body which can be (lightly) screwed down to block the outlet and stop the leak. As the system has not been recently filled I would have no problem doing this myself but would occasionally open the cap to check for any collection of air.

Other than that you are stuffed and will have to at least release pressure on the system (if sealed) or bung the header tank and drain the system to a point at which no water would leak out. If you're brave you could do it semi-live, release pressure than do a fast changeover remembering to have the new valve threads generously taped (in the right direction) with PTFE tape and that a size 8 thumb will staunch flow for a short while if you need some thinking space. Have plenty of old towels to hand.

Good luck

[Heliotrope Smith]

"Nigel Heather the-heathers.co.uk>" The automatic air vent in my heating system is faulty - basically it leaks

No need to drain down to replace the auto air vent. Just depressurise the system (best not to use the pressure relief valve, a litre or two from a drain c*ck should bring gauge to zero) and change the AAV.

[Nigel Heather]

Think I have fixed it.

Its a Braukmann (Honeywell?) Automatic Air Vent. You can twist the whole body to close the valve and turn the vent off altogether.

I then unscrewed the told of the vent and you get the float and arm which closes/opens the air vent depending on the float position.

There was a lot of balck residue caked on this so I cleaned it all up and screwed it back onto the main body.

I then turned the body to open the water valve and 'touch wood' it seems to be working now - no leaks.

At least I now know that if my fix hasn't quite worked I can buy a new vent (for £18) and just use the top on the old body.

Thanks,

Nigel