Tub gurgle

[Daywalker461]

I have a gurgle from the tub that comes and goes when toilet is flushed. Sometimes it’s loud and sometimes it’s softer. Sometimes it does not gurgle. Not sure what’s going on. Long ago I had a backup, was snaked, use root kill routinely and no problems since with backups downstairs. The backup was caused when washing clothes. I have been on the roof, vent looks to be clear. Here is an attached picture of my plumbing. The tub plumbing is the closest to the wall. The roof vent is attached to the toilet. Any help appreciated.

 

[Cacher_Chick]

From what I can see in the photo, it does not appear that the tub drain is vented properly, so when you flush the toilet, the trap on the tub is being siphoned.

 

[Sponsor]

 

[Reach4]

Your tub does not appear to have a vent on its p-trap. It is possible that when you drain the tub, the trap siphons out, at least partially. So when the toilet sends a blob of water, and it pushes air. You say there is a roof vent for the toilet. So maybe that handles that air, but maybe not well enough.

Maybe an AAV for the tub trap arm would let the tub trap retain more water and not let the air push its way to the tub so easily.

I am not a plumber.

 

[Terry]

Normally the tub would have a vent before entering the line with the toilet. An AAV for the tub may help with that.