How would you connect this new stack to the public sewer?

[mike42]

We're at the early stage of planning a new extension. We are thinking to add a new bathroom one a side of the house that currently doesn't have a stack. I've attached a diagram (north is up) where you can see the proposed new 2 story extension and proposed new stack on the left (west) of the house.

There is an existing 4 inch sewer server 3 houses and ours that runs through from south to north and the existing manholes are shown as rectangles. Its fairly shallow at about 500mm at the bottom half to around 750mm to the other side.

So I've been wrestling with how that new stack could be connected up. My two thoughts are either:

1/ Run a new drain going north from the new stack and connecting in to the manhole on my side of the boundary shown in the garden north of the house. The problem with that is there is a shed and base in the way (in the gap on the left) so wouldn't be able to get any minidigger in there and the shed foundations might be in the way.
2/ Since the west elevation is not really viewable and has few windows, I was thinking I could run the stack south along the side of the building - i.e. almost horizontal. Then around the corner have it go underground meeting the manhole right round to where it says "Connect Here?" in the diagram. With that I don't understand what is allowable on the side of the house (would I need two vents?) and as you can see the manhole there is only 500m to the invert so any drain going from the SW corner of the house would be pretty shallow?

diagram here:
https://www.dropbox.com/s/pdpib03e0bnm8ne/drains.pdf?dl=0

As ever on this fantastic forum, any comments or advice much appreciated !

 

[noseall]

I would be tempted to go down-stream and avoid having to skirt around or fuss about dealing with the new extension.

Having said that, because of the shallow depth of your preferred IC, you may be in a position to dig and pour the foundation concrete and still be able to run the pipe across site prior to building any foundations masonry, if you decide on your preferred option. It just does not flow as well as heading in the other direction.

 

[cjard]

Why are you putting a new stack on a side of the building that (on the attached plan) doesnt seem to have any waste water requirements? What does the upstairs floor look like? How thick is/can your floor be? (if the ww is only required on the upstairs, you can run the pipe across the house internally if you're set on conencting into the drains in the passageway

There appears to be a manhole in the front garden, half way along the run to the boundary of the existing drains; why is that not a consideration? it's less than a day's dig for a machine..

 

[mike42]

Many thanks indeed for the suggestions. Yes the ww would be upstairs only.

It is starting to look like the manhole in the front garden might be the easiest place? Can a stack have near-horizantal (e.g. 40:1) runs in it so that it could route outside on the western wall heading north to the garden at the front perhaps going underground at the NW corner. Something like this for the west elevation? And would I need VentA or VentB or both?

VentA............ VentB
|.................... |
|.................... |
|.................... WC connection
|.................... |
|.................... |
|.................... |
|.................... |
|.................... /
|.................... /
|.................... /
|.................... /
|.................... /
|
|
|
|
-----------------------Ground

 

[cjard]

40:1 is bordering on too steep; go for 80:1 instead. **** pipes are ugly, get them into the stack and get the stack into the ground asap