Aghhh... Pressure/air release valve pis*ing water

MrThrifty

Drained central heating system today to do some work, then refilled after and bled all rads etc. Then I turned on the circulating pump and as you'd expect there was a bit of hissing from the pressure release valve above it (at least that's what I always thought it was! Brass coloured yoke with a small screw-on red cap on top...). But next thing I know, there's water pis*ing out of the thing.

Thought it might be a quirk, but no, water now continuously comes out of the cap even with the pump off. I screwed it down fully for now but is there a simple fix to this?! Is it just a bit of dirt stuck in the PRV and keeping it open or do I have to replace the whole thing?

crosstownk

It might be dirt but if it won't shift then you'll have to remove the valve to clean it so you might as well fit a new one and be done with it.

Pete67

Sounds more like an automatic air vent (AAV) than a PRV to be honest. It could be a bit of dirt lodged keeping it open but I'd just replace it to be on the safe side. Not expensive.

AAV looks like this:

MrThrifty

Looks like an AAV alright - says 10 bar, 110 degC or something like that on it. Anyway, another problem soon presented itself shortly after this one... Boiler safety stat tripped after a few mins plus a few worrying noises from the pipes!! Issue was never the AAV... Sorted now, but I'll leave ye guess for now what it was!!

Pete67

Either air in the system, or circ pump failed/seized?

MrThrifty

Close, but you're ruling out human error/stupidity! Hadn't primed pump properly... I also didn't mention that after initially refilling the system I had the boiler on with the pump going (or so I thought) for a min to check it was still grand after the summer. Presume air/hot water in boiler pipes built up pressure which then was pushing cold water further along the pipes out the AAV if that is possible. Cringe...

DoneDL

If the AAV doesn`t reseat then replace it or clean it. If you can leave the air vent cap loose without water coming out then you should be ok.

MrThrifty

Out of curiosity, do you clean the AAV by removing the top cap or via the base piping connection point? The main metal top part looks like it's threaded to the rest of the body, but it can't twist as the protruding plastic threaded vent (that the red cap goes on) goes through it. I was thinking that maybe the protruding plastic vent thing might screw off and this might allow the metal top cap twist off. Where's a pic when you need one!

MrThrifty

No need - worked it out for myself. Interesting yokes! Oh yeah, found a chunk of metal or some sort of debris at the top so hopefully this is the cause of some of me probs!

DublinDilbert

Are you sure there is water circulating? It might not be and pressure building up. Your pump might be air locked, you can try bleeding it on the screw in the rear.

MrThrifty

D-Dilbert, see 6th last post...