Placement of durgo / air admittance valves

You need to install one air admittance valve at a position higher than the spill over level of your highest appliance, normally the Basin.

If it's the only vented soil pipe in the house then you can't install an air admittance valve.

 

If it's the only vented soil pipe in the house then you can't install an air admittance valve.

Don't understand that one. I've seen plenty of houses (mostly new) that only have an admittance valve, even owned one.

I'm sure the building regs say they should be in an unoccupied part of the building (not in a cupboard) and if you have lots of houses then every so often you need a normally vented stack

 

I've seen houses with them in too tgs, in fact I've installed a fair few with just the one stack! however the building regs do state that they are not permissable if it's the only stack.

 

Hmmmm interesting my guide to building regs hasn't made that point clear.

 

If the whole street decided to install durgo's where would the system vent.. hence building regs...

 

I think its more to do with the position of the house on the run of the drains.

Apparently you're not meant to durgo the end of a drainage run (Underground run), so if your one of the first houses, you're OK, if your the last then it's a vent through / around the roof, allegedly !!

 

Does anyone know why the Durgo must be placed above the highest flood level?

Reason I want to know is that I can't understand the logic.

For example, if you had a WC and a basin on a stack, and the stack became blocked, then any water would overflow out of the WC pan, preventing the water level rising anywhere near the level of the water in the basin, or the Durgo, provided that it's higher than the lowest flood level - in this case the WC.

I am about to redo the bathroom at home and delete 1 of the 2 vent pipes in the house and cap one with a durgo. The entire point of this scheme is so that that I can have a continuous work surface with a semi-countertop sink in it. Clearly if the Durgo has to be higher than the sink, then I can't put it below the level of the worktop, ruining my scheme...

So far I've failed to get a decent answer on this one! I'm not interested in a quotation of the regs - I've read them - more an actual explanation of the reasoning behind the reg.

Thanks!

 

It isn't to do with flooding, the valve is one way. It's to ensure that the pressure equalisation can occur without breaking the trap seals.

 

MechEng,

I wouldn't worry too much about having the AAV under the worktop in your Bathroom, this sort of thing happens all the time. I've got two Bathrooms on the go at the moment where the AAV is getting placed under the W/top and the vent pipe removed.

The thing that's always puzzled me is that it's perfectly OK to have an Anti Vac trap on your Basin which is below the spill over level but it's not OK to fit the AAV below the spill over??

 

I agree Bstyle. All seems a bit weird. I'm going to put it under the worktop anyhow.

I honestly can't see that the a few inches vertical height would seriously affect the pressures acting on the system with regard to trap seals being broken? I'd heard the argument before, and was going to put an anti-vac trap on the sink to counter this, although I still can't fathom the reasoning!

Cheers