40mm waste steep gradient required.

I am converting a bedroom into bathroom and I am trying to work out a way of connecting the bath waste to the soil stack without any pipes showing.

I would like to run the waste pipe between the joists, through a wall, then add a 90 degree turn. This latter section will run along the wall and connect to the soil stack. There is a snag, to get the latter section to connect without disturbing extension roof tiles and flashing it will need to be at a gradient so that it falls 50cm in 1.5m length. This is a steep gradient and I am concerned that I shall end up with syphoning or slow draining problems.

====================================================== Can anyone advise whether this scheme will work and meet building regs or come up with an alternative? Could this scheme work if an air admittance valve was used? ======================================================

Full details are: Soil stack internally vented via durgo, connected to a run with open vented stacks up slope. Bath waste 40mm pipe, first straight run (between joists) is 3m long and can have 18-40mm fall.

Thanks for your help in advance!

|I am converting a bedroom into bathroom and I am trying to work out a |way of connecting the bath waste to the soil stack without any pipes |showing. | |I would like to run the waste pipe between the joists, through a wall, |then add a 90 degree turn. This latter section will run along the wall |and connect to the soil stack. There is a snag, to get the latter |section to connect without disturbing extension roof tiles and flashing |it will need to be at a gradient so that it falls 50cm in 1.5m length. |This is a steep gradient and I am concerned that I shall end up with |syphoning or slow draining problems. | |====================================================== |Can anyone advise whether this scheme will work and meet building regs |or come up with an alternative? Could this scheme work if an air |admittance valve was used? |====================================================== | |Full details are: |Soil stack internally vented via durgo, connected to a run with open |vented stacks up slope. |Bath waste 40mm pipe, first straight run (between joists) is 3m long |and can have 18-40mm fall. | |Thanks for your help in advance!

Mine has a slope much greater than that, had no problems at all. Bath wastes run only partially full so siphoning is impossible if there is a continuous fall. Someone else will remember how far away the bath waste must be from the toilet junction to the soil stack.