I recently had the plumbing get backed up and snaked out. Things are working much better now, however, there are certain conditions (notably the use of toilet paper in conjunction with a shower or the washing machine) which result in extremely slow draining for the whole house. This also results in the showers backing up (slightly) and the sinks gurgling.
I'm thinking that the main line may need to be snaked another 20-50 feet but I want to rule out anything within the house. The main is the only common drain between the various rooms impacted so the only other thing I can think of would be the vents.
How can I tell if this is a problem in the main line or in the venting?
Edit: city sewer. At the end of a dead end road if it matters.