No vents on sink or tub. AAV help?

[itsttl]

So we are gutting the bathroom due to a leaking tub and toilet. The only thing that didn't link was the sink, amazingly. We had to sister studs, replace underlayment, subfloor, etc etc... the only problem is we want to put new fixtures in and I want everything to be code. I have been debating on using an AAV (studor vent) to rectify the lack of venting for the tub and sink but I am wanting to make sure there are no other glaring safety concerns on the design of the cast iron vent stack. It seems to me that having the water rush down the toilet pipe past both the sink and tub would suck the water right out of the traps since the sink/tub inlet are between the toilet and vent riser. We have never had a problem before and we never notice any smells but I know it can't be right. As for the AAV for the sink I want to make sure I can put it in the vanity 4" above the sani-tee. I am pretty sure it is 4" since it is not the MAIN vent (that would require 6" above overflow) but again, not a plumber, want to check. I have taken some high resolution photos and used paint to show proposed changes. Thanks so much in advance for any assistance you may provide.


Image gallery:
http://imgur.com/a/RM0Mm

 

[Terry]

Normally I would have guessed the tub and lav were going into the vent and that the santee and 90 to the right were for the toilet.
The lav should have it's own vent, which could be an AAV 4" above the trap arm.
The lav could then vent the shower if it's on the same 2" line.

 

[Sponsor]

 

[itsttl]

Thanks for your reply. The sink and tub are on the same line so I am indeed venting it through a AAV under the sink. Quick question: At the store there were a studor "redi-vent" and a "mini-vent". I chose the "mini-vent" because it was more expensive and had a higher DFU number. Upon getting home it seems I only require a DFU of 3 which the "redi-vent" would have covered. Did I waste money or is this a case of "you get what you pay for"? I ask because I may have to install one of these in an upcoming kitchen island. Thanks.

 

[Terry]

Having had a double wide on a farm with a failed "cheater vent", I'm inclined to buy the good ones now. Please don't make me think of how that one smelled.

 

[itsttl]

Just an update. I filled the tub all the way and capped the toilet and while the tub was draining (1-1/2" drain) it wouldn't even hold a piece of paper to the stub out on the sink (marvel connector) as there was no suction so I feel a lot better just using a studor vent. No sewer gasses for me I am also happy I bought the best... well, at least the most expensive Thanks Terry