Downstream Venting Question

[Jeremiah]

Hi there! I'm brand new to the forums and pretty new to plumbing, so please forgive me in advance for any ignorant questions.

I am currently attempting to properly vent a bathtub and a washing machine (which are essentially back-to-back), but I have run into the challenge of not having any space for the vents (this area was never properly vented by the previous owners, so I'm trying to correct that as I modify the plumbing). The plumbing is, by necessity, under a large bathtub, so I would need to run a horizontal vent in order to get out from under the tub (at less than a 45 degree angle below the flood level of the tub, which is against code). I have a vent nearby, but I am not sure if code would allow me to use it as a vent for these fixtures. According to the IPC:

911.2 Connection at the same level.
Where the fixture drains being common vented connect at the same level, the vent shall be at the interconnection of the fixture drains or downstream of the interconnection.

Here is the positioning of the plumbing:

My question is this: Is the vent considered downstream of the shower and washer drains?
Anything beyond the wye connecting the shower and washer drains is downstream, but the vent is actually upstream of the sweeping tee that joins to the main drain line, so I'm unsure of how to interpret this.

Thanks in advance for any insight that you can provide!!

 

[Stuff]

That doesn't count as a vent for these otherwise it would be too easy to have one vent for the entire house! It could count as part of the shower's wet vent if only bathroom fixtures on that drain.

Washer should have its own vent and it's drain needs to join after the shower's vent so as not to suck the water out of the shower's trap. Vent also needs to be above the fixture trap. Otherwise it becomes an S-trap which is not allowed. So you either need a vent pipe for the washer going up the wall or an AAV.

 

[Sponsor]

 

[Jeremiah]

Thanks, Stuff!! That is really helpful information. Luckily, there are only bathroom fixtures on the drain, so I can wet vent the shower as you suggested, and I found a way to vent the washer up a wall (the real problem was trying to vent both of them up the wall, so you did me a big favor by suggesting that!). Does this look better?

 

[Stuff]

The devil is in the details so now you need to figure out what the pieces need to be.
Do a read through http://www.co.lincoln.or.us/sites/d..._-_helpful_hints_residential_construction.pdf for lots of good info.

 

[Jeremiah]

Thanks again! That document has a lot of great information in it, and it helped me to spot a couple of flaws in my plan.