Ventilating Stub Stacks with AAVs

[Nigel DK]

I'm building a new build bungalow and have 3 stub stacks coming up through the block and beam floor.

I will be installing an external Soil Vent Pipe at the head of the drain, but I am unsure of how to terminate/ventilate the 3 stub stacks.

My ideal solution is to put an AAV at low level behind the pans. This would mean I can use combination vanity units and wouldn't need to box in and terminate the stub stacks in the loft.

I know if you install a type A rated AAV you can fit it below the flood level of sinks, so it could in theory be installed behind a pan. However, it does say it needs to be installed in a place with good ventilation. Is the back of a pan, inside a vanity unit considered good enough for ventilation?

How do you all terminate stub stacks? I don't recall seeing lots of boxing in every new build bathroom I've seen, so I assume they must be terminated behind the pan?

 

[oz-plumber]

Why do you need so many vents?

There are distances from the ventilated drain, that you can run without having a vent.

 

[Nigel DK]

Why do you need so many vents?

There are distances from the ventilated drain, that you can run without having a vent.

I've tried looking this up in the building regs (Approved Doc H) but can't find anything clear. The regs do say that stub stacks don't need ventilation if they are connecting to a ventilated drain, which mine will be.

However, it does seem a long distance back to the vent pipe. I essentially have a main manhole connecting to the sewer main and then two drainage runs coming from that manhole, one going anti-clockwise around the bungalow and the other going clockwise around the bungalow. One of the stub stacks will be around 35m away from the soil vent pipe.

 

[oz-plumber]

If you have an unvented drain with a run of 35 metres then you need a vent.
I would not rely on an AAV to vent the drain, you need a vent to atmosphere.

What you have to determine is what part of any drain is classified as vented and what is not.

 

[Ben-gee]

If it’s running right around the bungalow just tee up for a vent towards the high end of the drain run.