We are having a new bathroom fitted. The plan is that the waste pipe from the washing machine (which is located in a utility cupboard next to the bathroom) will travel through the bathroom wall and run under the shower tray. About halfway along, the washing machine waste will be intersected by a waste pipe from the shower. Both have Hep VO valves on them. From the intersection, the waste will go directly into the main soil pipe as the previous waste pipe disappears down into a concrete floor and is too fragile to attempt to use. The previous waste pipe will be capped. I am uncertain whether any further Hep VO valves will be used. I have been previously advised that waste from the washing machine and shower should be kept separate so I am a bit confused by this plan and concerned about potential smells, blockages etc from the soil and waste pipes. Can someone tell me if the proposed plan is ok, any questions I need to ask, additional stuff which might need to be installed?