New toilet and sink connection with Air Admittance Valve

[soultraveler]

Hi everyone,
I live in British Columbia, Canada
i am planning to make a bathroom in my second floor bedroom.
The main stack is pretty far away from my bedroom. So, i do not want to break the floor, wall, and studs to connect my solid line to the main stack.

1. so, i am wondering is it possible to connect my toilet and sink to the main stack from the outside?

2. for the venting problem, i am planning to attach an Air Admittance Valve(AAV) on the top of the outside solid line. The AAV i am getting is an abs 2" X 1-1/2" thread-on adapter. 20 DFU'http://www.homedepot.ca/product/abs-air-admittance-valve-with-threaded-adaptor/968663

The reference from this site states that 1 bathroom and 1 sink has around 9 DFU. In my case, a 20DFU AAV would be good enough right?http://www.vbgov.com/government/departments/public-utilities/rates-fees-charges/Pages/drainage-fixture-units.aspx

3. Do i need another dry venting? If so, can i just add another AAV under the sink ?




Any help would be nice
Thank you

 

[Matt30]

You have an S trap on the sink. Replace the 90 after the trap arm with a tee wye and take the vent off the top. The drain must be 2" since you are trying to wet vent the toilet off the sink. The toilet must also tie in the branch ahead of the sink.

 

[soultraveler]

Hi Matt
thank you for your advice
what about this?
i have added another aav under the sink.

Also, would there be a problem adding two 90 degree bends under the sink before the p trap?

 

[johnjh2o]

Increase A to 2" with a 2x1-1/2 tee for the lav and you can eliminate A.