Retrofitting internal SVP

[Shevek]

Do you think building control (approved inspector) will go for this (sketch attached)? We're fitting a new internal SVP to take a new bathroom and en suite + plus existing toilet and a new basin and washing machine at ground level.

The existing WC connects directly into drain at floor level and then goes down and through foundation wall and is cast in a big lump of concrete. So it'd be nice to avoid having to dig it up if there's a way.

View attachment drainage.pdf

 

[nicro3]

The stub should be branched into the underground section with a 135 deg branch (existing) You can try to get approval but most BI would like it in this way. Hope this helps.

 

[chris watkins]

Not doable I am afraid there will not be enough room to get a 135deg branch in plus the branch in for the WC at 190mm off of the floor. Why do you need the stub stack ? Connect the stack above the WC con.
You will need to confirm that there is a minimum of 450mm from the invert of the existing 100mm clay drain to the first connection to the stack, to avoid compression at the base, how deep is the run outside?

 

[Shevek]

Not doable I am afraid there will not be enough room to get a 135deg branch in plus the branch in for the WC at 190mm off of the floor. Why do you need the stub stack ? Connect the stack above the WC con.
You will need to confirm that there is a minimum of 450mm from the invert of the existing 100mm clay drain to the first connection to the stack, to avoid compression at the base, how deep is the run outside?

Thanks Chris, we do have more than 450 mm from the invert of the existing drain.

I thought we needed the stub stack to connect the ground level WC/drainage but perhaps I'm thinking of taller buildings. I was also thinking it could provide rodding access.

And I was also trying to avoid an offset in the stack but I've effectively created this anyway with the connection into the stub stack (the stack needs to offset to avoid bath above).

So you think just run stack into existing floor connection. And then offset above to avoid bath?

 

[chris watkins]

Thanks Chris, we do have more than 450 mm from the invert of the existing drain.

I thought we needed the stub stack to connect the ground level WC/drainage but perhaps I'm thinking of taller buildings. I was also thinking it could provide rodding access.

And I was also trying to avoid an offset in the stack but I've effectively created this anyway with the connection into the stub stack (the stack needs to offset to avoid bath above).

So you think just run stack into existing floor connection. And then offset above to avoid bath?

Sounds much better. You could sill have access cap above WC con just move 135deg branch above WC one, just watch no connection zones with the two.

 

[Shevek]

Thanks Chris. I also sent that sketch to my Approved Inspector and he got back to me this morning and approved it. But as you point out it's not build-able. So I'm going to send the attached revised sketch. Do you think I need to add rodding access to the stack just above the offset or would rodding access from the end of the en suite WC branch connection be enough?