When I was testing the 2nd floor master bath plumbing I was running the water at both sinks. They drained fine.(Or it seemed so at the time) I left the water on at the sink to test the flow.
When I went to test the tub plumbing the water from the sinks was backing up into the tub.
The home has been vacant for awhile.
As you see in the pic it appears there is some sand/grit debris.
Do you think the problem is with the tub plumbing or would you advise the hole DWV system be scanned.
It seemed just to be the master bath that was an issue, Toilets flushed OK. First floor Half bath OK.