Connecting to a gully underground with a shower waste

[John Williamson]

Planning a wet room with a flush floor where the waste will run through a slab and through the wall to discharge to the drains outside. Using something like the below bottle gully, would building regs allow me to connect the shower waste underground in one of the top two 40mm inlets?

As far as I can tell the Approved Document H says yes but just wanted to make sure I wasn't misinterpreting them.

 

[John D v2.0]

Yes that's exactly what those entrances are for. It's not allowed to be splashing around or overhead for health reasons I assume.