AAV quickie

[Temp]

On 25/03/2020 at 07:30, andy said:

They are insisting that I have to have a penetration through the zinc roof for the furthest connection from the mains sewer and an AAV is not acceptable

 

That's a common request from BCO. I think it comes from this bit of Part H...

 

Quote

 

2.18 The system should be ventilated by a flow of air. A ventilating pipe should be provided at or near the head of each main drain. An open ventilating pipe (without an air admittance valve) should be provided on any drain fitted with an intercepting trap (particularly on a sealed system),and on any drain subject to surcharge. Ventilated discharge stacks may be used (see paragraphs 1.27 and 1.29). Ventilating pipes should not finish 
near openings in buildings (see paragraph 1.31).
 

 

 

However I believe that actually refers to the last house in a row of more than 4 houses. See page 11 in this document..

 

https://www.bpfpipesgroup.com/media/29598/Air-admittance-valves-for-domestic-properties.pdf

 

It suggests that if the row is 4 or less houses (eg one house) all the vents can have AAV.

 

I've seen this mentioned before but don't know where the justification comes from.

Edited March 27, 2020 by Temp

[Temp]

Same info from Floplast..

 

https://www.ribaproductselector.com/Docs/5/12945/external/COL912945.pdf

 

5.2 To contribute to the ventilation of the underground drain and to minimise the effects of excessive back pressures when a drain blockage occurs, the branch or main drain serving a stack or stacks fitted with a FloPlast valve may require a venting point upstream of the stack connection. For guidance the following should be noted (see figure 4):


● For up to and including four dwellings, one, two or three storeys in height, additional drain venting is not required.

 

And Hunter Plastics according to...

 

https://job-prices.co.uk/durgo-valve/

 

Several Durgo Air Admittance Valve manufacturers, including Hunter Plastics and Floplast have published the following information, although it doesn’t appear to form part of the official regulations:

For up to and including four dwellings, one, two or three storeys in height, additional drain venting is not required. Where a drain serves more than four such dwellings equipped with the valve, the drain should be vented…

 

[andy]

Thanks - we're at the end of a row of a few houses and they all have external vents.  I suggested to our BCO that we don't require one due to this but they won't budge.

 

Unless I can calculate this value, I'm stuck with putting in an external vent - Where these valves are used they should not adversely affect the amount of ventilation necessary for the below' ground system which is normally provided by open stacks of the sanitary pipework.

[Temp]

I suspect the "four house" advice is based on work AAV manufacturers commissioned at the BRE or a similar research body. I haven been able to find that. I would try asking some of them if they can write a letter to justify your use of AAV without an open vent. Send them a simple diagram of your row of houses showing yours with an AAV and the other houses with open vents.

 

Ask them...

 

"Can they confirm the guidance in their literature (enclose a copy) is applicable to your situation and that you would not need an additional open vent to meet section ?? of part H which states "Where these valves are used they should not adversely affect the amount of ventilation necessary for the below' ground system which is normally provided by open stacks of the sanitary pipework."

 

The alternative might be to try and do the calculation on page 10 of..

 

https://www.bpfpipesgroup.com/media/29598/Air-admittance-valves-for-domestic-properties.pdf

 

That calculation is about sizing the AAV you need based on the flow rate from your appliances. It's not clear that's what your BCO is asking for but it's the only calculation I can see being possible.

 

 

[Temp]

Are you planning a shed or other outbuilding? Might be possible to extend the drain there and put an open vent on that?

[JFDIY]

11 minutes ago, Temp said:

Are you planning a shed or other outbuilding? Might be possible to extend the drain there and put an open vent on that?

Good idea, 

Or an extended a leg on the network, down the garden up the side of a fence post . 

 

 

 

[Mr Punter]

I think you can put the vent pipe from the below ground into a shrub border at the back, away from seating or dining areas..  Just a 600mm upstand with a rodent proof mushroom cap would do.  Because it is vented to atmosphere you should not detect any odour.

[Temp]

and once the BCO has signed of the house I'm sure you could make it "disappear".  

[Pete]

2 hours ago, Mr Punter said:

I think you can put the vent pipe from the below ground into a shrub border at the back, away from seating or dining areas..  Just a 600mm upstand with a rodent proof mushroom cap would do.  Because it is vented to atmosphere you should not detect any odour.

Yes you can, that is what I have to do to satisfy my S/Insp

[MJNewton]

2 hours ago, Mr Punter said:

I think you can put the vent pipe from the below ground into a shrub border at the back, away from seating or dining areas..  Just a 600mm upstand with a rodent proof mushroom cap would do.  Because it is vented to atmosphere you should not detect any odour.

 

You could always just plant such a pipe and pretend it's connected up.. ?

[Pocster]

51 minutes ago, MJNewton said:

 

You could always just plant such a pipe and pretend it's connected up.. ?

I hear you !