Air Valve Thingy!

[Barney12]

Sorry, another plumbing question. 

I beleive this is an automatic air release valve (its got a red niple on the top not in the photo).

Can anyone tell me what I seat this into? It's smaller than 1/2 bsp.

it came just as photographed

[Jeremy Harris]

That looks like a 3/8" BSP one to me, one of the ones that has a shut off valve so you can unscrew the top part for servicing without draining the system down.

[gravelld]

Looks like the same AAV that ruined my Christmas 2015.

[Nickfromwales]

6 minutes ago, gravelld said:

Looks like the same AAV that ruined my Christmas 2015.

Was it crud in the water that actually ruined Xmas . 

Any contamination finds its way to the float valve in these AAV's and blocks the pins resulting in water coming out of the cap at the top. 

14 hours ago, JSHarris said:

That looks like a 3/8" BSP one to me, one of the ones that has a shut off valve so you can unscrew the top part for servicing without draining the system down.

+1

[Barney12]

Thanks guys. It is indeed. Reducery thingy obtained from Screwfix.

[Jeremy Harris]

As a tip, you can unscrew the black part from the brass part to clean the valve if it needs it, without needing to drain the system down.  There will be a small amount of leakage as you unscrew the black part - the faster you unscrew it the less there will be.  If you wrap an old towel around the thing it will soak up the small amount that dribbles out.

[Barney12]

23 minutes ago, JSHarris said:

As a tip, you can unscrew the black part from the brass part to clean the valve if it needs it, without needing to drain the system down.  There will be a small amount of leakage as you unscrew the black part - the faster you unscrew it the less there will be.  If you wrap an old towel around the thing it will soak up the small amount that dribbles out.

 

Ta. That's good to know as it's part of the sealed GSHP loop which will be a pita to drain (not to mention expensive because of the antifreeze) 

[Barney12]

On 09/08/2017 at 11:07, Nickfromwales said:

Was it crud in the water that actually ruined Xmas . 

Any contamination finds its way to the float valve in these AAV's and blocks the pins resulting in water coming out of the cap at the top. 

+1

 

Well what do you know. My AAV seems to p*ss water out of the top. I’ve had to screw the red cap down for the moment. 

Is it serviceable or do I just go buy a new one? 

[Jeremy Harris]

They can be taken apart and cleaned.  You can remove the one with the type of service shut off valve yours has, by unscrewing the top part quickly.  The bit with the O ring on then rises up to block the hole and stop any more water coming out.  It will leak a bit as you undo it, and make sure you hold the lower brass fitting secure as you quickly unscrew the top. 

 

To clean them out, the top cap can be unscrewed from the body.  They are often a bit tight to undo, but the seal is an O ring in the top.  You can then lift the float and lever arrangement out and wash out any muck that is holding the thing open (it doesn't take much).  When it's all clean reassemble it and refit it by very quickly screwing it back into the brass fitting.

 

Putting an old towel around it when taking it on and off is usually enough to absorb the leakage.

 

These things do have a bit of a reputation for blocking like this, as any tiny bit of buoyant crud can find its way to the tiny air hole where the valve is, and jam it.  There is a far more expensive type that pretty much never gets blocked, and that's the Spirovent.  Personally, I'm of the view that the best way to use ordinary AAVs like this is to leave the caps open whilst you initially set the system up, to allow any air to bleed out, then shut the caps down and treat them like manual air vents, unless you have a specific need to continuously vent a system that accumulates air for some reason.

 

You could buy another one the same as you have, and just swap them over, cleaning the blocked one in slow time and keeping it as a spare, as they are not that expensive.

 

Heating systems in general shouldn't need automatic vents, as there should be no reason for gases to build up, although I know from experience that this can happen, as it happened to our old central heating system, and was eventually put down to there being two different makes of inhibitor in it, as when drained the water came out all frothy, full of gas and milky-looking.  Washing it through with clean water for an hour or so, then refilling with Fernox, fixed the problem completely, and since then I only ever put the same type of Fernox in it , and the problem hasn't recurred.

 

We have a Spirovent fitted on our main water feed, as our water is heavily aerated as a part of the treatment process, so there is always a lot of dissolved air that if I don't remove ends up as small air pockets that then make the taps spit a bit.  The version of the Spirovent I have is one that includes a stainless microbubble collector, so it takes pretty much all the air out of the water before it gets to the rest of the house.  I doubt that you need anything like this on your system, and would suggest that using your AAV as a manual vent, closing the cap and just periodically opening it to see it there is any air collected in the cup, is probably good enough.

[Nickfromwales]

Is there any merit to adding a Y strainer before these AAV's in systems that have ferrous components or part existing pipework being recommissioned ?

[Jeremy Harris]

1 hour ago, Nickfromwales said:

Is there any merit to adding a Y strainer before these AAV's in systems that have ferrous components or part existing pipework being recommissioned ?

Not sure, but there might be.  The problem is really that the vent hole is tiny, less than 1mm in diameter inside, where the silicone seal closes it off, and it only takes a really small bit of buoyant crap to get in there stop the seal seating properly. 

 

All the buoyant crap in a system should really just be from initial assembly, little bits of sealant, bits of plastic etc.  When one of ours jammed, what came out when I washed it was a tiny bit of black plastic, that I couldn't identify, but assume may have been a bit of lost moulding flash from the UFH flow gauges, as they were the only bits of black plastic I could find.  Once the initial crop of crud has floated up to the AAV, I would think the chances are that things should be OK from then on.

[Barney12]

Thanks Jeremy. I’ll have a play!

[Moira Niedzwiecka]

This sounds like something else to worry about.

After, hopefully, solving the issue of not having to have an SVP exiting the house but a low level one venting from the manhole outside I could just have a couple of AAV's in the house above the level of the water in the loos.

I did not realise that access to these would be required & had thought I could build them into internal walls.

I had thought they were just venting & no water would be involved.

Is this not the case??

Sorry to be so dim.

[Nickfromwales]

As they have moving parts they can fail. 

If they fail, you get foul stench coming out of them. 

Basically they allow air to be sucked into the sewer when the loo gets flushed and the falling pipework had a full slug of water in it, falling vertically. For a short period during this event, in some pipe arrangements ( but most problematic where it falls one or two floors ), you get a vacuum created in the soil pipework.That vacuum can suck water out of basin / shower / bath traps and then foul stench can come out of them, until waste water replenishes the traps. The AAV is there to mitigate against that problem. 

You could argue it out with the BCO that a basin trap with AAV inbuilt would suffice if the invert between the soil outlet of the WC and where the groundworks soil turns back to horizontal ( heading to the manhole ) is less than 1300mm. A 110mm AAV would be overkill in that scenario, and if you can demonstrate that working to the BCO they should agree to let you do away with the 110mm AAV and just stick with the basin / other aka secondary mitigation measure.  

Some Bco's are stubborn and won't agree to that in principal but they should be ok after a successful demo. If it's falling more than iirc 1300mm it's a 110mm AAV every time. 

[Jeremy Harris]

The building regs require access to AAVs for servicing, in fact it was one of the the things the BCO confirmed with me before giving the go ahead to fit one.  I fitted ours in the eaves space, as our house in room-n-roof, so there are sizeable crawl spaces down either side.  You can fit them so there's a removable service panel, but they do need an air supply to operate, so need to be somewhere where they can draw in air.  There are several ways of providing a service panel that might work.  In one house I fitted a shower valve that needed rear access for maintenance to a tile that I fitted in place with sealant, rather than tile cement.  I did once have to get at it and it wasn't too difficult to cut around the edge and remove the tile to gain access.

[Nickfromwales]

Posh ones

 

Not so posh ones

 

Both available in different sizes.  

[Barney12]

Am I right in thinking that AAV's have to be above the flood line. I.e. Higher than the bath/basin overflow?

[Nickfromwales]

Above the top of the WC pan makes sense, but as high up as the basin overflow could be right. Downstream of the AAV would have to be blocked solid for this to be an issue, but as soon as the water got as high as the WC pan it's going to oveflow there way before the basin trap. 

[Moira Niedzwiecka]

We will have a downstairs loo under the stairs & a shower room with a loo above, but offset.

On the other side of the house we have a bathroom with a loo above the utility room.

I was hoping to duct the internal SVP's & incorporate them in dividing walls as the bathroom & shower rooms are quite small because of the pitch on the roof (chalet Style house)

Would we need SVP's for both sides of the house with AAV's on them?

I can have them both going up into the warm roof space so the valves could be a 7ft+ above the sink or loo.

They would just not be very easy to access & may have to have a bend put in to get under the large glulam roof beams.

[Nickfromwales]

You only need one vent to atmosphere and the rest can be AAV's. 

The vent to atmosphere is purely a requirement, per dwelling, to vent the gasses that acclimate in the sewerage network rather than what your home produces . 

The vent can be outdoors as a dumb riser off the foul water manhole and be in smaller 75mm ( 3" ) soil pipe. It can be at the rear and out of site or even at ground level at the periphery of the plot, hidden by plants.