Im adding an addition on and I was splicing into the existing plumbing. I dont want to overload the drain but wasnt sure whats too much. I would have a washing machine, 2 different bathroom sinks, kitchen sink, dish washer and a shower all on a 2″ line, the same line. Thats the easy fix… but is it okay? With a bunch of extra work I can put in a 3″ line, letting all the fixtures run about 2-4′ on a 2″ line util they reach the 3″ line… if that would be better???
This is a common question (what size DWV pipes do you need to handle the drainage of plumbing fixtures) and fortunately there is an easy answer. The plumbing codes describe “fixture drainage units” based on the discharge flow from various plumbing fixtures (toilets, showers, lavatories,etc. Follow these code guidelines, and you should be OK.