I am in the process of building a new utility room and am looking to minimise the drainage requirements for a dishwasher, sink and washing machine. The utility room will be adjacent to an existing outside toilet (to be retained) and I noticed today that the sink next to this toilet drains directly into the soil pipe just below floor level as shown in the photo (sink waste pipe is the grey pipe on the right). Is it acceptable to adopt this setup for my new plumbing i.e. could I have the appliances feed into a trap which then drains directly into the soil pipe below floor level?