Wrong durgo AAV size used?

[amandaebr]

Hello
If someone could offer some advice with an air admittance valve sizing issue please.

We recently had a house renovation including a loft conversion, the loft now contains two bedrooms and a bathroom.

The plumbers have installed an air admittance valve within the boxing of the toilet in the loft, this is the third toilet in the house. The AAV is 40mm and rises from the top of the toilet waste pipe. See photo.

We have had some issues with odours and what we consider poor flushing. It is a 1960s detached house. Each house on the road has its own SVP.

We have looked at technical docs and BS 12056-2. This suggests the flow of the AAV is a calculation based on the number of water using fixtures and what they call intermittent use (domestic house).

We have kitchen sink, dishwasher, washing machine, 3 basins, 2 baths, 2 showers and 3 toilets.

We cannot find anything definatively which states that a 110mm AAV should be used at the top of the toilet waste however many diagrams show this. It looks as if a 40 mm AAV is really only suitable for use on pipes from basins and for fewer fixtures.

Please could somebody confirm IF a 40MM AAV is suitable in this situation, should it be a 110mm AAV internally, 110mm air admittance valve externally or is a traditional soil vent pipe better?

Thank you for reading.

 

[denso13]

Soil vent pipes for a stack should not be less than 75mm diameter. This is to the open air but it would make sense for an AAV to be the same.

It is always better to have an open vent to the outside if possible.

 

[Gasguru]

Looks a bodge to me...100mm AAV required. I'm not sure what document would say so...but it would be stating the obvious.

A traditional SVP is best, 110mm AAVs can be used externally provided they have the approvals...only some manufacturers produce them, otherwise if an AAV is used internally is must be in a vented duct/space and must be accessible for maintainance.

Ultimately the job needs signing off from building control...give them a ring and seek their advice.

What's that screw doing in the AVV?

 

[amandaebr]

Thank you to both. So we need to insist on at least a larger AAV internally but preferably an outside SVP or external spec AAV.

Gasguru - Building Control were uncommital as to size required, just said to manufacturers guidelines..

See what you mean about the screw, shouldn't be there, but we noticed a crack yesterday so maybe to secure it?

 

[denso13]

So we need to insist on at least a larger AAV internally but preferably an outside SVP or external spec AAV.

Yes, sounds like a plan.

 

[amandaebr]

Another related question please.
Would this wrongly sized AAV cause poor flushing of solids in the ground floor toilet? We have had it overflow from the back (where it joins into the old soil pipe) twice.

Thank you.