Wet Vent and Air Admittance Valve Questions

pete0403 · 10-29-2012, 03:13 AM

Hi,

I'm planning a plumbing run for a drain and I need to work out the details of the cost etc before I put together a plan. I think I have an idea but it might be all wrong so I want to run it by the experts here first.

The drain is going to be for a plastic basin that will be used for bathing dogs and it will have a good 20 - 25 foot straight run. 95% of the time it will only have to handle the drainage of the hand sprayer. I will have a cleanout (or 2) due to potential dog hair clogs.

First question: Refer to the first picture below...where the drain will come out of the wall (red circle) there is a small vent right there for my washer standpipe. Would this be a situation that I would be able to drain into this vent and create a wet vent? Standpipe in basement would be wet vented, basin 1/2 level up would be wet venting.

Distance from standpipe to stack:

Where the small vent attaches to the standpipe drain:

Second Question: The configuration of the rooms between the basin and the standpipe would make it very difficult to run a vent. Under what circumstances would an air admittance valve be allowed?

Thanks for any guidance and ideas. I live in Ontario incase rules on these two questions vary from place to place.

Edit: The basin will have an 1 1/2" drain, the vent is 1 1/2" and the standpipe drain is 2"

**TheEplumber** · 10-29-2012, 11:55 AM

Your running about 20 ft of drain line 4ft above the floor? Adding a vent near the end of it is not needed. The vent needs to be near the tub's trap.
Why not run an indirect line from the dog tub to your existing laundry tub? Then you won't need to cut into the stack

pete0403 · 10-30-2012, 12:10 AM

Thanks for ther reply.

I'm not asking about adding a vent, I'm asking if I can use and existing vent as part of my drain line (creating a wet vent). My house is a split-level, the drain running along the floor of my "upper" basement will come out of the wall 4' up in my "lower" basement.

I don't really want to run an indirect line because we will eventually be finishing our lower basement then I'll have to figure out what to do with it then anyways. Plus I assume 20 feet of drain will eventiually make the area stink (think wet dog hair...yuk!).

So, Can I use the vent as part of the drain? And can I use an AAV by the tub?

Thanks,
Pete

**TheEplumber** · 10-30-2012, 12:43 AM

You should tie into the vertical 2" copper- that appears to be a drain from upstairs? You can then put the AAV at the tub trap.
Per UPC code I work off of, a wet vented section should be 2" as well- so the washer vent is undersized.
You can get shielded no-hub couplings that transition from copper to plastic when you cut in your wye.

pete0403 · 10-30-2012, 06:28 PM

Thanks a lot for the info. I was hoping not to have to cut into the copper stack but if the vent is undersized then that's what I'll have to do. The only other option is to run the drain down to the 2"standpipe drain at the horizontal portion but that might be too awkward.