Your waste plumbing is done in 4″ sewer pipe which feeds into the sewerage. Your other fixtures will feed into that in their relative sizes. Toilets are plumbed straight into the 4″ sewer pipe while baths and sinks and showers etc. are in 2″ pipe and have to be reduced to go into the sewer pipe. The exception is the bathroom vanity sink which is usually 1 1/2″ pipe.