Air admittance valve...

[secret squirrel]

Just getting my head round these and this relates to a previous post earlier today.

It concerns an air admittance valve, I need to replace one and the current one is below the fill line, I've looked about and now understand these "bad boys" a bit more. Floplast do one that can be below the flood level but above the 100mm above the connecting waste.

This is a bit different to what I've read.

Any views?

 

[Hugh]

Buddy never seen one of those bad boys your talkin about, all the ones i have fitted have to be above spill over level, but fittings are gettin more advanced each year good luck!

 

[TGor]

I think installing an AAV below the spillover of the highest fixture is a dangerous practice even if the manufacturer says its's OK.

After all it's your responsibility if the device fails ... and what are you saving a few feet of pipe only!!

There has been a reluctance in the US to adopt these devices into the plumbing codes as it is felt that their use could be abused as is obviously happening here!

 

[secret squirrel]

TGor,

I agree with what your saying 100% my only concern is that its clearly visible and the extra bit of pipe will look ugly.

Better that than a flood though.

Thanks All

 

[TGor]

I agree would look terrible but swvp's are not meant to be pretty!!!.. the AAV was developed to cut out the cost of roof penetrations and save a bit of pipe ... might be better looking to run the VP up to the roof space and stick the AAV up there .. you might even get away with 50mm which you could run in a corner .. check the regs.

TG

 

[Plouasne]

Try this link, it will tell you more

Brett Martin - Building - Soil & Waste - Design

 

[secret squirrel]

Plouasne, that is a really good link thanks.

I've got one more question to do with air admit valves that I can't find the answer to.

In my area there seem to be a lot of air admittance valves on the outside of bungalows. Everything that I've read so far (I'm a bit of an anorak) says they should be on the inside of the building because of freezing etc.

Why would this be done? if it was just one or two I'd say people (diyers/plumbers/builders) being a bit lazy.

Is there an aav designed for outside?

 

[TGor]

Yep, most of them are .. Studor range from -20 to +60 deg C The only reason for the AAV's is to save money on running vent pipes to high levels. It's a matter of opinion whether it's the best practice or not!

cheers
TG

 

[Winston]

I have seen a few fitted externally and thought this was a no no.

 

[david williams]

yet another degridation of plumbing standerds,they may prevent syphonage but can do nothing for backpressure which can also be a problem in soil and drain systems

 

[Bernie2]

Hmm!

Yes, AAV are good to get out of awkward problems, but I would not fit them as standard. They don't do anything for back pressure and if you get a blockage you'll know what I mean.

And yes some can be fitted on the outside, but that is only a difference of position.

The old drainage systems where intended to be ventilated throughout their length, obviously AAV's don't do that.

I suppose we will have to wait for a couple of spectacular sewer gas explosions to be in the news before anybody cuts back on AAV's. Lets hope and pray nobody gets hurt.

 

[secret squirrel]

Thanks Bernie,

Reading your reply answered another question that was running about my head and that was "if you fitted an AAV why does the building insp want it vented still to the outside, although in a much smaller pipe"

I now have a much better understanding of these.

 

[HTB]

If I remember my regs course correctly every 10th house MUST have a "proper" atmospheric vent to prevent gas build up, this is to stop developers taking advantage of the new regs re: AAVs.

 

[buffy27]

buf is back.....
lads whats the story with sufficient air ..for the intake in the aav's. i have seen one used in a very much air tight boxing a while ago and have often thought about it afterward . this was a real posh pad in dublin...presume the house is still standing!!!!!!!!