We just purchased a home that was built in the 70s. The second floor has 2 full baths and one on the first floor below that. All 3 bathrooms share the same main vent. The second floor guest bath has the strongest odor and the master bath has it slightly. The first floor bath has no odor.
Based on other posts we determined that there is a clog in the vent line. When the tube drains we hear gurgling as it goes down. We think it is only a partial block considering the water drains very quickly. We tried to snake the line from the roof, but still have the odor. Is it possible that the branch pipe coming from the smelliest bathroom has the clog instead of the main pipe? If so, what is the best way to unclog it?
Thanks
J

When the tube drains we hear gurgling as it goes down.
Any gurgles when when the vanity drains or the toilet flushes?
You are correct! Your tub is attempting to vent through the trap and the resulting suction could pull the trap seal down enough to allow sewer gas to escape.
When you snaked from the roof vent did you get the correct lavatory vent and did you put out enough snake to reach the base and 20 feet more? Let me know, Tom

No gurgles when the vanity or toilet flush! We're going to try the snake again and make sure we put enough out. There is only one vent pipe out the roof, so we're going to try to snake the right one.
Thanks
J

There is only one vent pipe out the roof, so we're going to try to snake the right one.
That was going to be my next question,
All plumbers hate this set up.
Sometimes a contract will call for only a single vent to exit the roof.
We then proceed to tie back every vent in the house to a single roof vent. This is just dandy until you have to snake a certain vent.
When that happens we have to lug our equipment up in the attic, locate the correct pipe and cut it loose before it can be snaked. We then have to test our work and if the vent's cleared we reconnect the vent back that we had to cut.
Unless you're willing to go through this you had best call in a plumber./
There will be more labor involved upping the charge but that's then price you have to pay for a clean roof line. Sorry to be the bearer of bad news. Good luck, Tom

Thanks for the help Tom! We were afraid of that. I bet you all hate it. We are starting to hate it too. We were able to snake one line that was close to the top of the vent. We'll see if that helps with the smell. Does anyone make a vented cap that you can put on the top to prevent foreign objects from getting in there?
Thanks Again
J

Does anyone make a vented cap that you can put on the top to prevent foreign objects from getting in there?

There sure is,(see image) but most of us simply cover the pipes with large opening screens. Good luck, Tom

Thanks Tom! We'll look for a screen. I think the squirrels are getting at it. As luck would have it the branch we snaked seemed to be the right one. The smell has disappeared.
Thanks Again
J

Thanks form the update. Tom