Is this tub vented properly?
Hey all I am looking for some help on my tub venting. The house is 40 years old. The picture attached is what the plumbing looks like. I have had the toilet off and run water through so I know the sink and the tub both connect under the toilet and then go to the septic.
Both the sink and the toilet are fine and I think they are adequately vented based that the roof vent is on the same wall with them. The tub doesn't have a vent and its pipe goes across the bathroom floor then ties into the toilet.
When you shower, there is an inch or so of water in the shower and the tub gurgles through the overflow vent. I have made sure no hair, etc is clogged on the X part of the drain. Would adding an air admittance valve on the pipe where the tub overflow connects to the drain give me more venting for better draining?
Thanks a lot