AAV valve - height/interpretation of manufacturer's spec

[Tim Watts]

It's kinda a bit after the fact - but I wonder if anyone would mind seeing if they agree with my interpretation of Floplast's instructions.

Page 2, lower right dia and page 3 lower right dia says:

AAV 200mm above highest joint

It does not say "highest joint in the room / on any sub branch"

So I read that (8 years ago and again today) as "200mm above highest joint on the *main stack* - ie the 110 bit that the AAV sits on top of.

That seems to be implied by Page 2 as it's 200mm above the branch to the bog, which in many normal houses will have a basin tapping into that as soon as it's through the wall.

Floplast appears to differ to others who require their AAVs higher and explicitly above all appliance flood lines. That's why I picked them.

Mine's behind the bog, about 300mm above the top of the side branch to the tee which the bog connects, inside ventilated boxing.

AAV | | | | --Rim of Bog-- | | | |______ |O_______Bog | | =======Floor===== | | | | | |

O leads off to a basin on 40mm

Reason for thinking now:

1) I have to do the same in the shower room. That's less ambiguous as the basin uses a separate stack. Shower bog has boiler and washing machine standpipe just through the wall on 50mm coming in on the bog tee like O above.

No AAV yet as GasSafe fitter said not needed until bog was there and we needed the tiling done first, which is now done.

2) Going for The Great Sign Off with BC as soon as the shower room is completed. Now on BCO #3 who I have never met - and it's now a merged multi council group. Just want to have my reasoning ready for the new guy...

BCO #1 did query the first AAV and I explained Floplast's instructions verbally as I understood them and he seemed happy but we did not pour over the diagrams.

It's not impossible to make them higher, but it would be ugly - and in the shower room, I would have to drop to 82mm, use an eccentric adaptor to get it far enough off the walls as the soil pipe is quite close to the base plaster (we left some of the tiling/backer board out to accomodate a 110 fit)

[Tim Lamb]

In message , Tim Watts writes

I've gone by the rule of making any AAV higher than the overflow level of any tackle on the same branch.

>

[Tim Watts]

That went through my mind - but I counter argued to myself "well, it's only the bog rim that really matters, because any blockage and it'll overflow that first".

I should add the 1st AAV is working fine and has been for years... This is more about justifying it with a straight face to the BCO as he may ask (he might just be happy BCO #1 noted it down as OK - I do not know the extent of my file, I may have to talk him through *everthing* and it's that I'm preparing for).

[nothanks]

10-15 years ago I had the same quandary. I had a secondary stack with a garage sink feeding in on the ground floor and a basin, loo, bidet and shower on the floor above. I didn't want the AAV to be higher than the counter top so persuaded the Building Regs guy that, because the garage sink would indicate a problem looong before the problem was evident upstairs, I could have the AAV slight lower than the highest item (the basin).

[Tim Watts]

It seems reasonable...

I imaging the real problem is if water gets to the AAV valve along with lumpy bits, that then impede the flap sealing correctly.

There's no way that can happen with mine without the bog overflowing.

It's also possible that I could exchange the stack AAV for a branch AAV or HepVo (inline AAV) on the basin branch. Not quite sure. But I'm slightly more dubious about about a HepVo going wrong compared to my setup anyway.

[Jim GM4DHJ ...]

as long as it is not outside...I have seen dozens outside......

[Jim GM4DHJ ...]

hope BC are not going to do a pressure test as I found only Marley made one that held a pressure test.......

[Tim Watts]

BCO #1's approach was to ask the builder (who dug the new drains):

"did they hold water?"[1]

[1] You bung the final outlet, fill up the manholes with a hose and wait...

Very trusting....

[Jim GM4DHJ ...]

very unnecessary but acceptable...

better to use a smoke box ....or high tech manometer...tee hee

[Fredxx]

I'm intrigued by this thread and how this article implies you can replace a stack with an AAV.

My understanding was the stack was there to cope with over-pressure in the sewer pipework, as much as admitting air.

Fitting an AAV will mean that sewer gases will enter the house past the syphon traps, and against current BCO rules.

[Jim GM4DHJ ...]

You can't JUST have an AAV you must have a vent at the highest point of your system ....

[Jim GM4DHJ ...]

then again a hundred years ago you had disconnecting six inch traps Buchan traps in the pavement and the sewer was vented separately.......

[Jim GM4DHJ ...]

don't think that is quite true....if you are a developer you only have to vent SOME of the houses you build on a new site.........

[Andrew Gabriel]

Some other comments on AAVs...

They do occasionally jam open, so you need to have relatively easy access to pop it off the top to clean the cobwebs out or to replace it, so don't leave it fixed behind walls/panels which make it inaccessible without destroying decorations.

Another comment is that the vent pipe doesn't need to be full soil stack diameter providing soil stack is no higher than first floor. It can be reduced to what works out to be standard gutter downpipe size (which I can't recall offhand). Maybe that allows you to extend it up to open outside rather than using an AAV?

[Tim Watts]

I have an open vent outside on the far end of my underground branch which deals with positive pressure.

The AAV is to prevent the loo sucking the basin/boiler/washing machine traps dry on the internal 110 branches. I do know the AAV is not pointless as I can hear it operate occasionally (usually loo paper which I guess forms a plug with the flushing water. Those branches drop about

2.5 ft before going 2-5m underground to the nearest manhole.

I did not fit an AAV to my 3rd internal branch as that only takes the bath/shower/basin/kitchen. It's impossible (in theory) to form a water piston to cause any suckage.

[Tim Watts]

As per last post, I have that too - outside. On 82mm pipe (as permitted by regs). :)

[Tim Watts]

Indeed - I have loose tops on the boxed in section and the AAV will pull straight out (with a stub of 110 pipe in one case, it was a solvent AAV IIRC - the other one I'll use push fit AAV, but same idea)

That'll be 82mm.

[Tim Lamb]

Building reg. drawings usually show basin waste runs greater than 1.7m in 40mm and 50mm for bath and basin runs over 3m.

I fitted AAVs to both the ground floor and upstairs bathroom stubby stacks and a 40mm valve for the combined bath/bidet/basin wastes. There was always an external stack vent pipe but BC wanted it extended because there was a conflict with the nearest openable window.

[Tim Lamb]

In message , Andrew Gabriel writes

The one fitted to the farmhouse by our builders gave a lot of trouble. I think linked to draining hot bath water. The replacement is trouble free (25 years).