Soil stack advice (moved)

[R_Nott]

Currently planning a bathroom renovation, where we want to swap the positions of the bath and toilet. Due to this, the soil stack will have to change.

Current stack is this:

PXL_20220126_094438153

• R_Nott
• 26 Jan 2022

Toilet soil pipe coming from the right, this is roughly where the bath outlet will be

PXL_20220126_094435708

• R_Nott
• 26 Jan 2022

Bath waste to the top of the T on the left. Boiler condensate popping out the wall to the left of the T, with a boss adapter to move it up to 40 mm. Toilet soil pipe will be to the right of the current bath waste.

My first thought was to rotate the current soil Y branch 180 degrees. The direct line from the branch would overshoot the planned position of the toilet soil pipe (see below, overshoot in grey, planned hole in red), so I considered adding a 135 bend to make it vertical underneath the point where it comes out the wall.

Rotate Stack

• R_Nott
• 26 Jan 2022

However, building regs seem to say that soil pipes should be 18-90 mm drop in 1 metre. That would mean that I can't go vertical, and even the angle of the current Y is too steep. Is this right?

New plan was to replace some of the stack. Add in a T-piece higher up, and pop in some bosses for the 40 mm wastes. This can be seen in the diagram below.

Soil Stack

• R_Nott
• 26 Jan 2022

Problem is, there seems to be a lot of issues with potential crossflow. The coloured boxes and stated measurements in mm show the limits of the pipe centres based on building regs limits of 18-90 mm/m for soil and 18-44 mm/m for 40 mm waste. Not a lot of leeway for any of them.

Does anyone have any advice?

 

[R_Nott]

Moved from my projects

 

[Hugh Jaleak]

Either option with the 110mm from the WC will be ok, the fall (drop) is referring to long 'horizontal' runs.

Wastes are easier to reroute as required, anything coming from the came side as the WC will be fine, connections opposite need to be at least 200mm below the centreline of the WC branch.

 

[R_Nott]

That's great, thanks for the reply Hugh. Just to be clear, either option A or option B below would be fine, with the no go areas for the bath waste on the opposite side to WC branch shown in red?

Soil Stack 2 Options

• R_Nott
• 27 Jan 2022

Regarding the condensate, would there be any problem putting in a strap-on boss for it in the area marked in blue on option A? This would bean blocking the boss in the area marked orange. The other possibility would be to stick with the current boss position, but that would mean have to do a really contorted route to get around the vertical part of the 110 mm branch.

Finally, with regards to the bath waste, would it be possible / sensible to use a boss branch such as this, which would mean that the waste would be 90 degrees to the soil, so not opposing, or would it be better to avoid the 200 mm zone completely and use a strap on boss further up or down the stack?

 

[Hugh Jaleak]

Yes, avoid any opposing connections in the Red areas.

Condensate connection should be fine in the blue area. I'd keep any external run as short as possible to reduce risk of it freezing.

Bath waste, will be fine going into the side of the junction is you can get the height right, (usually bath waste will be coming out the wall lower than the WC outlet if using a 92.5° Soil Junction), otherwise it's fine to connect at any point if coming in from the same side as the WC connection, the 200mm zone only applies to opposite connections to prevent crossflow blocking the waste connection.