said by ttiiggy:
These involve the 3" main and multiple 1-1/2 drains and 2" vents that are in a tight location and spaced quite close together.
You've got to use PVC that is clean & dry--no lubricant!
With existing setups sometimes there's just not enough flex in the pipes to be able to bend & fit them. A couple times I've used Unions to make an otherwise difficult connection, and for drains a rubber coupling/sleeve (with hose clamps) can help you (the pipes mate face-to-face and you slip the sleeve you've slid onto one of them over the gap and secure with hose clamps).
If you call Ask This Old House and get Richard to come-over there, by all means let us know--he'd figure the best way to do it!