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Hello,

I am attempting my first channel drain and am trying to link it to the underground drain but am told i need a foul air trap between them to pass building regs. Ive got a p trap in place but has to be reversed to work in this scenario due to space restrictions and small difference in height between channel drain and underground drain. See attached picture. Its not working properly at the moment, but my question is should this set up still work with p trap flipped around? If not has anyone got a better solution or different type of trap? Thanks

Hi spare_ribs98
Move your drainage channel to the left in you picture and fit the foul air trap.
Regards S

Hi Stoneyboy,

Do you mean shift the channel drain across then fit trap directly to the channel, and with trap other way round i.e. the normal way?

Hi spare_ribs88
Your u-bend fitting is just, well, a u-bend. You need to get a foul air trap on the inlet side of the u-bend so move the channel over enough so that you can fit a foul air trap after the two 45 bends and before the u-bend.
Regards S

Hi spare_ribs88
Having looked at you photo again I think I may have given you the wrong information - sorry - you may not have enough height difference between the channel and the soil pipe connection. The u-bend does need reversing and you could try short 90 deg bends to see if there is sufficient difference. The foul air trap does need to be above the level of the soil pipe and below the level of the drainage channel, so unless you can lower the soil pipe connection you may have to consider installing a soakaway.
Do check your local water board is ok with you discharging surface water into their foul drainage system before you go any further.
Regards S