Re: Air Admittance Valve - advice

[Jonathan]

Hi Harv,

I've been looking at these devices as I will have to do something with all the soil pipes and stacks when I extend my house. I'm not entirely sure but I think the air admittance device might need to be above the level of any traps. On a downstairs loo that connects to its own soil stack, not say the main one form the upstairs bathroom and loo, I think it might only need to be above the height of the downstairs loo's wash basin. I'd have to go an re read the building regs from the website that holds them to be sure. Also look at websites like Marley or Hunter Plastics, Hunter is a small company and might be forthcoming if you email them and ask their advice.

Cheers

Jonathan

[Harv]

I'm fairly sure the regs say that the valve should be above the level of the trap for the handbasin.. but I was wondering if there was any reason why is shouldn't be just slightly below the level of the basin trap - it would certainly make life much easier.

This is all in theory of course... ;)

Harv

[BigWallop]

Hi Harv,

If this stack is an outlet from a WC, then get ready for the smells Sir. A soil stack should vent to air, if at all possible, as it vents rather unpleasant gases and fumes into where ever the end of it is.

Would it be possible to take a couple of bends and take the pipework out through a side wall of the room and then rise ? I don't fancy the idea of it venting into anywhere I'd like to spend some relaxing time.

The air intake valve must be a minimum of 500mm above any appliance using it, to prevent any damage from soiled water spillage due a block in the pipework forming the drainage system, and must be given an access opening for the purpose of clearing any blockage. So if you are thinking of an air intake valve, then you'll have to fit it on top of a branch pipe with local access eye to be able to clean through the pipework.

Hope this is of some use.

[IMM]

Harv,

Don't use an air admittance valve. Put an inspection cap above the toilet on the stack. I assume the basin is pied into this stack around where the wc is connected to the stack. You only need to use a Hepworth HepVo trap on the basin, nothing else.

See the web site:

[Danny Monaghan]

"BigWallop" wrote in news:GgcPa.7211$ [e-mail]:

Forgive me if I'm not following this, but isn't the whole idea of an air admittance valve that it let's air in to stop syphoning from vacuum, but doesn't let air, and therefore smell, out?

[IMM]

Yes. But you get the occasional smell and thump as it drops onto its seating. HepVo is the better bet here.

[BillR]

The valve should be above the overflow for the basin.

In theory, mine don't. They are least 1m above anything that can feed into the stack

[IMM]

If a 1 metre pipe above the wc is in the way use HepVO. They say, and it does:

HepVO actively eliminates negative pressure within the waste system by opening and allowing in fresh air until a state of equilibrium with atmosphere is reached. This means that venting of the waste system, or the inclusion of air admittance valves in the waste system is no longer necessary.

[Harv]

I've seen the hepvo traps at the plumbers merchants, but didn't realise they could be used in this manner. Is this in breach of building regs at all?

Also, I hadn't mentioned, but my neighbours toilet/basin also feeds into the same stack, presumably the one hepvo valve will be snough to deal with this?

The only problem I can ever see is if some smart alec ever moves in and replaces the hepVO with a conventional trap, at which point, a trap from one of the 2 baths, 2 basins and 2 toilets would get syphoned.

Many thanks,

Harv

[Harv]

I should have mentioned that the valve will be boxed in behind plasterboard.

[Harv]

Replying to my own thread.... as I realised just after sending, that I guess the valve could obtain the air through the overflow?

[IMM]

It is always best to have two on the system, as the probability of both basins being full is remote. If installing the air admittance valve is not a problem, then fit both.

[Harv]

Got hold of one last night - looks a very handy piece of kit, need to get the elbow fitting to see if I can get it to fit to the existing wastes, can't really make a new hole through the wall, as tiling would be ruined.

The houses on the row all share the stacks at the rear of the house - 2 bathrooms (1 each) per stack. I was just unlucky in that my house was the one with the stack, next door already has a conservatory, so requesting they use their own stack is not really practical.

I can't really imagine him being keen to fit a hepvo at my request, he won't be best pleased at the roof I'm putting on because he was responsible for the carpentry (wood butchery) in the old one.

Will see how things work with just one.

In place of an AAV?

[IMM]

You can have a spigot from the basin through the wall and have the HepVo in another "accessible" position. I have seen downstairs toilet have the HepVo in the garage. easy to get at and if cleaning al the mess in the garage.

Should be fine.

Yes.