Master Bath - Wet Vent Toilet & Fixture Horizontal to Trap

I've learned a lot from these forums, but I'm still unclear on a few things even after reading the Illinois Code and two plumbing books. Please see the attached isometric drawing of my master bath remodel. The additional water closet, washing machine and sink are for an existing bathroom and laundry room on the same floor.

Thank you very much for your help!

1) Wet Vent Toilet

I'm unclear about the horizontal branching connecting to the water closet bend (red text below from the Illinois Plumbing code). Does this mean the horizontal branch (wet vent) from my shower must connect directly below the water closet or can I connect the horizontal branch from my shower to the water closet as shown in the attached pdf? In other words, does the term "water closet bend" imply the entire branch to main drain or another branch?

Section 890.1500 Installation of Wet Venting

f) A single bathroom group of fixtures, consisting of a water closet, lavatory and a bathtub, shower or floor drain, may be installed with the drain from a lavatory serving as a wet vent for a bathtub, shower or floor drain and for the water closet, provided that:

1) Not more than four DFUs drain into a 2-inch diameter wet vent; and​

2) The horizontal branch is a minimum of 2 inches and connects to the stack at the same level as the water closet drain. The horizontal branch may also connect to the water closet bend. (See Appendix K.Illustration S.)
​

2) Fixture - Horizontal to Trap

I'd like to avoid drilling a hole through my joist in the basement. Also, I have a drop ceiling that's hung about 2 1/2" inch's from the joists. Thus, I'd like the drain for my shower to come down through the floor, go horizontal 8" to the joist (16 o.c.) and then put the union trap under the joist. This makes it into the next bay where I can turn, put the vent in and drop down running 2" to the toilet with a clean out on the end.


Any other words of wisdom are greatly appreciated as well!

 

I could not view the file you uploaded, and would need to see the drawing to understand your intentions. The shower drain needs to drop vertically into the trap. A running trap further down the line is not permitted.

 

Here is his drawing as a JPEG:

 

Thanks Reach.

The water closet needs to be vented within the allowed trap to vent distance, regardless of whether the vent is wet or dry. Think about a 2" pipe at 1/4" per foot pitch. If you exceed the allowed distance, the vent can be broken, and the liquid trap will be effected.

 

Is a running trap that is less than 24" away permitted?

Section 890.410 Fixture Traps/Continuous Waste

b) Distance of Trap to Fixture. The developed length from the fixture outlet to the trap weir shall not exceed 24 inches, except that an interceptor used as a trap shall be located as close as possible to the fixture. The maximum developed length from the fixture outlet to the inlet of the interceptor shall not exceed 5 feet. (See Appendix D.Illustration B.) The standpipe inlet for an automatic clothes washer shall not exceed 48 inches above the weir of a trap.​

Here's an updated illustration (jpg). The water closet is long sweep + 2'4" from vent . So I should be within the allowed distance. Correct?

Thanks for the help!

 

The running trap would not fly here, but we are not under the same plumbing code. I would avoid it regardless, because the buildup in even 2" of horizontal drain before the trap is eventually going to make for a stinky smelling shower.

 

Understandable. Can I do a vertical offset with 2x 45s similar to the picture below, but with a short run of pipe between? Full thread on offset 45s.

 

This would be a common method of jogging a trap over to get clearance around a joist or other framing.