I am building a new building and was wondering if I should use 1 1/4" pipe to drain sink and lavatories like what was used in my house built 30 years ago are do I use 2" and reduce it to the size of the drain. Also what type of 4" pipe do I use for toilet drains schedule 40, 80 are other

This is per Florida Standard Plumbing Code.
We use 2" on all our fixture drains, Some codes are going to 3" on the kitchen drain because of the disposals.
Our mains and sewer lines are 4" schedule#40 and our toilet drains are 3" if it's a second floor installation and 4" if it's on a slab. Does this answer your questions? Good luck. Tom

Hi Rob

In Boston we pipe our kitchen sinks as 2" and are required to have a full-size 2" cleanout under the sink (always a good idea). We then reduce to 1.5" trap (with cleanout) and pick up the sink(s).

Lavatories get piped up as 1.5" to the 1.25" tailpiece that comes out of the lavatory pop-up assembly. You could also pipe 2" and reduce to 1.5" under the sink as Tom suggested.

As with Florida, 4" is the main drain size with a 4" cleanout within 18" of the inside or outside the foundation, but you can reduce to 3" after that as long as you have less than 3 toilet/bath combinations.

Washing machine drains should be 2".

A cleanout is required at the base of all waste stacks.

Finally, as you can see plumbing codes vary state to state, so it is a good idea to check your local requirements to be sure you only have to do this once!

Good luck!

Mark