Adding Shower to 1/2 Bath - drain and venting

[NewGuy]

I am adding a shower to a half bathroom. I want to use an existing sink branch for the shower branch. The vent and drain are 2" but I would like to use 1-1/2" for the first 3' (to the vent connection) of the shower drain if possible to reduce the hole size in the 2x4 (non-load bearing but supports cabinets). I am moving the existing sink the other side of the room and connecting near the washing machine on the opposite side of the wall. The bathroom is very small so this is the only possible layout to meet clearance codes. I have attached a rough sketch of the drain system. The only changes from existing are the small sink addition and shower addition (which is currently a sink drain). I have two options for reconfiguring the shower drain as shown in the drawing. Will this work? I was planning on using use sanitary tees/elbows for horizontal to vertical connections and long sweep for vertical to horizontal connections. Is a long sweep required for a dry vent (see top shower option in drawing)? Can I use 1-1/2" for the shower drain? I appreciate any help you can offer. Also this is a single story house partial slab/partial crawl space and the drains are all above grade in this part of the house (slope 1/4" per foot) except where the three drains drop through the slab and come out through the foundation wall in to a crawl space (the 45 degree double tee is located in the crawl space next to the foundation wall). The current drain system works perfect in the house so I don't want to do something to mess it up.

Thanks,

 

[Cacher_Chick]

If you move to Canada, the 1-1/2" shower drain will be permitted, but in the U.S., it is only good for a tub. 2" for the shower with a 1-1/2" vent. Anything below concrete should be 2" or larger.
The vent take-off must be done with a wye and 1/8th bend or a combo. The vertical "vent" directly to the right of the water closet serves no purpose and can be eliminated. The drain from the sinks could take a more direct route than it does. Add clean-outs on the vertical shower vent, laundry, and sink drains. While the sink drain is fine, it could arm over to connect above the washer sani-tee instead of going through the floor.

 

[Sponsor]

 

[Terry]

The shower will be a 2" drain, and you can run five feet between the shower and the vent.

The drawing looks pretty good. I prefer to use two 3" x 3" wyes, and not the double wye. Reason being, is that it's very hard to glue that in position and make sure it's not tilted down on one side. Using two fittings that allows for getting proper grade there.
At best with a horizontal double wye, it's going to be "flat".

As also mentioned, the shower could be used to wet vent the toilet if the vent is 2".

 

[NewGuy]

The shower will be a 2" drain, and you can run five feet between the shower and the vent.

The drawing looks pretty good. I prefer to use two 3" x 3" wyes, and not the double wye. Reason being, is that it's very hard to glue that in position and make sure it's not tilted down on one side. Using two fittings that allows for getting proper grade there.
At best with a horizontal double wye, it's going to be "flat".

As also mentioned, the shower could be used to wet vent the toilet if the vent is 2".

Thanks for the help everyone. One last question. The lowest I can get the bottom of the shower drain pipe is about 1.5" above the slab at the vent and 2.25" at the drain. I have an 8' ceiling. I can notch out for the p trap. I plan on using a one piece molded pan so no 2 stage drain is needed. Will the step be too high and will I be able to meet the 6'8" height code? Any options?

 

[Cacher_Chick]

I am not understanding your comment as the height of the trap under the shower will determine how high you can start the trap arm. From there you have to ensure that your tie-in to the drainage system is low enough to get at least 1/4" per foot of pitch. The vent take-off must rise vertically off the trap arm via a wye and 1/8th bend or a combo fitting.


The entire trap, drain, and vent take-off must be below the floor

 

[NewGuy]

I am not understanding your comment as the height of the trap under the shower will determine how high you can start the trap arm. From there you have to ensure that your tie-in to the drainage system is low enough to get at least 1/4" per foot of pitch. The vent take-off must rise vertically off the trap arm via a wye and 1/8th bend or a combo fitting.


The entire trap, drain, and vent take-off must be below the floor

In order to get the 1\4" per foot, the drain pipe will be above the slab 2-3 inches. I was planning on raising the floor for the shower about 10-12" for just the shower to accommodate the drain system. This will create a step up in to the shower. Because of the way the drain pipes go through the foundation, it would be near impossible to get it below grade without major demolition to the foundation and major wall.

 

[Cacher_Chick]

I would look at having the footing core drilled to put the connection on the outside if that resolves the issue. Raised showers scream "hack job" in my opinion, and are not good for resale.

 

[NewGuy]

I think I can limit the rise to 4 to 5 inches above the existing floor by notching out the p trap location. It' s not ideal but makes it possible to add the shower without major reconstruction. I do have a couple more questions. Can you drain a sink in to a stack above a clean out? Does the sink vent need a clean out if the horizontal drain is only a couple inches long (Remove the p trap under sink to clean out)?

 

[Terry]

Notching floor joists is a big no-no.
You need 2" above, and 2" below the hole in the joist. That's to maintain the structure.
You drain a sink either above or below a cleanout. Fixtures within five feet of a cleanout don't need one unless it's a kitchen sink line.

 

[NewGuy]

Notching floor joists is a big no-no.
You need 2" above, and 2" below the hole in the joist. That's to maintain the structure.
You drain a sink either above or below a cleanout. Fixtures within five feet of a cleanout don't need one unless it's a kitchen sink line.

Sorry for the confusuon. I would be notching out the concrete slab. I should have said cut out a hole where the p trap can extend below existing grade. I have a clean out on the washer vent and will add one on the shower even though it is probably overkill.