Best Route For Below Ground Foul Drainage?

[Stratman]

I would appreciate a bit of advice on drainage.  I will have 3 stacks: 1 from first floor ensuite and down to pick up kitchen, 1 from downstair ensuite, and 1 from first floor bathroom and down to pick up utlity.

 

Is it better to have as short a route as possible to outside the slab, then route them around the house to connect into the sewer, or shorter route 'as the crow flies' direct to a sewer? Both options via an inspection chamber to final connection to sewer.

 

 

 

Option A or Option B? ...or something else completely?

[Nickfromwales]

Option B is preferable, and my go to for each project. 
 

Option A would require a chamber at the top left (2x45°) where it changes direction. Another pot there for no reason imho. 

 

No need for an AAV in the downstairs loo btw, if the invert is less than 1300mm. 
 

Challenge the BCO if they’re stuck in their ways and push you to install one. Completely unnecessary here, and the only places you need these is at the first floor. 

[Stratman]

@Nickfromwales As a follow on question: do I have to have one of the stacks vented to outside or can they all have AAVs?  If possible I would prefer to avoid another penetration of the thermal envelope.  I find the wording of the building regs a bit confusing.

[Nickfromwales]

As you are a stand alone dwelling off the network you may struggle to get a deviation from the BCO to omit the SVP. 

 

An alternative is to have one rise on the external wall, on the side or rear where it’s not an eyesore.

 

If you plan that as a get out of jail card, then just don’t fit the SVP, and see if they notice . AAV’s will suffice. 

[saveasteading]

From memory only, you need an open stack at the end of the run. AAVs can be used elsewhere.

It's all in the building reg's  free online.

 

A, with extra chamber on bend , for me too.

[Alan Ambrose]

>>> you need an open stack at the end of the run

 

Is that at the treatment plant or the last inspection chamber nearest the house?

[Stratman]

20 hours ago, saveasteading said:

From memory only, you need an open stack at the end of the run.

Thanks for the replies. So far we have one vote for option A (with extra chamber) and one vote for option B.

 

Silly question perhaps, but one I can't find the answer to elsewhere: which stack is 'at the end of the run'?  The one furthest from the connection into the sewer or the one that's closest to it? I have all the approved documents downloaded but I find Part H difficult to interpret in some places.

[saveasteading]

20 minutes ago, Stratman said:

 The one furthest from the connection

A. I simply like to get drains out of the building by the shortest routes and keep things simple. Blockages are findable and outdoors. Also not in the way during construction.

B. With a bit of tidying up it works.

 

@Nickfromwalesis saying elsewhere that a flattish fall doesn't need an air admittance valve,and presumably vent, so it's worth checking the regs.

[Nickfromwales]

Ground floor doesn’t need AAV, for sure. 
 

First floor does (do) via AAV or SVP to atmosphere.

 

As I’ve put a bit of weight on, my vote counts twice. So 2 B and 1 A. lol. 

[Stratman]

Thanks - 2 to 1 it is!