Addition of a stub stack?

[Hux]

Looking for guidance please as I believe I have some challenges in considering the following  (please see image) -

 

1) SVP to rise (vertical arrow) from the basement invert, internally through the ground and first floors into the attic, terminated with an air admittance valve.  First floor will branch to family bathroom; toilet, bath, shower and basin.  Attic floor will branch to toilet, shower and basin.
2) SVP to branch (horizontal arrow) within the basement floor, 100mm above the finished floor (with appropriate fall) to serve kitchen sink (2m) and small enclosed WC (3.5m).

 

Current Issues:
1.A) Radius of the bend at the base of the main stack - The bend shown in the image is not appropriate as it is less than 200mm radius at the base of what would be the SVP.
2.A) Ignoring the second bend (temporary).  The 110 branch would be within 450mm of the invert of the SVP base bend and as such would not be appropriate.
3.A) Where the 110 soil pipe passes through the 9" solid wall, the cavity surrounding the pipe needs to be filled with compressible sealant.  What is a compressible sealant?

 

Doing anything with the main stack to make it serve any appliance in the basement is not viable?

 

Options:
1.AA) Provide a slower bend at the base of the SVP.
2.AA) Create a new stub stack, entering the building at the same level of the SVP base.  Running from external foul drain to the WC, incorporating a ventilated stub stack.  This would serve the basement kitchen sink, Basement WC's basin and WC's toilet, as the toilet is not higher that 1.3m above the drain invert.

I cannot conjoin the new stub stack to the main stack?  It will need to connect directly to the foul drain?

The foul drain serving the an additional stub stack could possibly (low) be subject to surcharging, combined with the sanitary appliance in the basement WC, the addition of an anti-flooding (one-way) valve on the pipe to the stub stack and toilet would be appropriate?

Or have I grossly misinterpreted approved document H.  Looking for some smart ideas here or means of simplifying the options above so that I do not have to run an additional 110 to the exterior foul drain to serve the Basement WC.

 

 

[Hux]

Seriously no input from anyone!  

[ProDave]

I would be looking to branch that pipe the other side of the wall, so 2 pipes come through the wall.  Then you can have your proper rest bend on the bottom of the stack, and have the run off to the right.

[PeterW]

What is to the left of the wall ..??

 

 

[PeterW]

Crossed with Dave but you need a full encased concrete rest bend on that vertical stack. 

[Hux]

To the left of the wall - a light-well at the front of the house.  The ground level of the light well is 500mm above the bottom of the soil pipe (as seen).  As the waste pipe passes the exterior of the wall, it bends left 90degrees then straight for 1200 then 90degrees right into the inspection chamber where is joins (perpendicular) the the main sewer.

 

If I branch in the light well.  Can the pipe to the rest bend drop down into the existing pipe from above it.  So two pipes would pass through the wall, one above the other.  With the one for the rest bend on top?

 

 

[PeterW]

I would be getting rid of the angles ..!! Go through the wall at 30 degrees and down to the next elbow otherwise you’ll have issues rodding any of this. 
 

Added a pic but you’re saying it’s like this on the top ..??  I would do it as on the bottom - last item is a swept T with a plug so you can rod this if needed. 
 

Edited April 1, 2021 by PeterW
Added pic

[Hux]

Unfortunately I can't go through the wall at the point shown in the bottom drawing.  

I need to retain the current entry point to the building as shown in the top drawing.

 

What would be the best way to separate the rest bend from the pipe that serves the WC.

Is it possible to branch them in the section external to the wall?  With the branch being vertically aligned and not horizontally.

So two pipes enter the building, one on top of the other?

 

[PeterW]

Ok this is a really bad design as you have a pair of 90 degree bends with no access for rodding or clearing in the event of an issue. 
 

What you are trying to achieve is challenging as you need to watch for changes in direction and to be honest unless you have a decent fall on the run to the sewer you are creating problems down the line. 
 

Is there any way you can bring the soil stack back from the corner of the basement for its entire height ..? You would need around 550mm back into the room. 
 

Has building control not queried this yet ..?

 

[Hux]

Peter.  Bringing the stack 550 back into the room adjacent to the wall would be possible.  How does that help with the two changes in direction?

[PeterW]

You would put a 45° Y fitting on the current connection then the rest bend at the bottom of the stack into the straight inline, then connect the WC to the branch. 
 

 

TBH I don’t like the two changes of direction - before you concrete this lot in  I would get Buillding Control to give it the thumbs up. 

Edited April 5, 2021 by PeterW
Not enough coffee before typing ..

[Nickfromwales]

1 hour ago, PeterW said:

TBH I don’t like the two changes of direction - before you concrete this lot in  I would get Buillding Control to give it the thumbs up. 

The last bend is rod-able from the inspection chamber so ✅ and the bend upstream of it is rod-able if you put an inspection socket directly into the top of the rest bend. 
If it were me, I’d have the Y branch and 45 to vertical as the rest bend, and that would allow the stack to remain in one straight line. Show BCO that the Y branch is to be set in concrete, so it’s not taking weight / cannot move, and you should be allowed a deviation here ( unless it’s the BCO I’m currently working with who is, in the words of James May, a cock. 

[PeterW]

Issue is if the first bend blocks then you have the volume / weight of the stack full of ... well, you know what, pushing back up hence the 45°

I’ve put in. Plus, this is basement so we have double stack above and BCO will normally insist on long rest bend (well will round here..!) as otherwise you end up with a slow moving poo pile at the bottom of the branch.. 

 

 

[Nickfromwales]

1 hour ago, PeterW said:

Issue is if the first bend blocks then you have the volume / weight of the stack full of ... well, you know what, pushing back up hence the 45°

Hog tripe. 
If the joints are sound, it’ll be “all good”. 
Rodding access plus the speed upon which things will be getting to at that last bend = near zero risk of blocking IMHO. Only a blockage at the IC would cause issue, and that’s not an everyday occurrence. 

[PeterW]

Which way up you putting the tee ..??? And where ..??

[Hux]

Is this what you mean?  With the addition of a long radius 90 bend, access point and then another 45 bend. The stack will rise straight in the corner.  Tis he Y branch vertically aligned to the pipe running off to the WC.

 

Keeping the stack in the corner really helps with its location as it rises through all floors.

[Hux]

Nick & Peter - thank you for taking the time to input on this.

 

@Nickfromwales, does the above sketch correctly represent your suggestion?  

 

Cheers

Huxley

[Nickfromwales]

 

@Hux

 

Add another access point to the right if that’s to be a convoluted run, but the above is what I would be doing. Stuff falling from above will be fired off to the outside wall via the 135 going into the Y branch and access next to will provide a point of maintenance if it ever blocks, which I doubt it ever will due to the addition of regular cross / through flow from the other WC ( iirc ) that is off to the right?