Maximum 4" soil pipe run?

[wanabechippie]

Hi.

Contemplating moving a bathroom from one side of a house to another(staying on 1st floor).

The proposed new 4" soil pipe (exiting the building) will be approx 8m from the point where the existing 4" soil pipe exits the wall but will be on the same external wall.

Building regs and planning accounted for; I'd like to run the new 4" pipe through the external wall, along the wall for the 8m or so and T into the existing vented stack.

Quandries:

1. - Is this possible or would there be an agreed 'maximum run' for soil pipes that is shorter than 8m?

2, - Am I right in thinking that over 8m or so, the drop should be 20cm (1:40).

3. - Does the soil pipe need to be vented at the point where it leaves the building, or will the existing vent (8m down stream) be sufficient?

4. - Is it ok to tie the shower and sink wastes into the same 4" soil pipe using a 40mm T (shower waste into sink waste) and a 4" strap-on boss into the soil?

Questions, questions...

Cheers.

 

[Softus]

1. - Is this possible or would there be an agreed 'maximum run' for soil pipes that is shorter than 8m?

It is possible.

2, - Am I right in thinking that over 8m or so, the drop should be 20cm (1:40).

Branch pipe gradients
The gradient of a branch pipe should be uniform and adequate to
drain the pipe and appliance efficiently. A minimum gradient of
18mm/metre should be adopted for 32, 40 and 50mm nominal size
pipes but larger diameter 82, 110 and 160mm branch runs may be
laid flatter at 9mm/metre fall where the discharge flow rate exceeds
2.5litres/second.

3. - Does the soil pipe need to be vented at the point where it leaves the building, or will the existing vent (8m down stream) be sufficient?

I would keep the existing vent, and add an AAV on a substack above the new WC position.

4. - Is it ok to tie the shower and sink wastes into the same 4" soil pipe using a 40mm T (shower waste into sink waste) and a 4" strap-on boss into the soil?

No - you should use 50mm waste pipe when combining shower and basin output.

 

[wanabechippie]

Okydoky!

Many thanks, Grand Master Softus!