So I flush a toilet at today’s inspection and see it swirl it’s way up to the rim then finally go down, whewwwwww (slow drain, clog,vent or improperly sized waste line issue)… then I hear water running behind me (all fixtures are off) yet the tub has a fairly steady stream of water running from it’s faucet for 10 - 15 seconds then it stops.
Flush the toilet again, water flows from the faucet again.
unfortunately the basement was finished so I could not confirm a definitive cross connection.
home was built in 1960, original water supply was a well - has since been changed to city water/sewer. One 2" vent visible on the roof, 3" main waste w/1 1/2 copper, 2" galvy branch lines coming into the tree.
What say you? agree, disagree?