Shop bathroom plumbing question

[westbrooklawn]

I know from previous posts that there is a lot of "building" expertise on this forum, so I'm looking for advice. I'm planning on adding a utility sink and 1/2 bath in my metal shop building. Use would be minimal. Configuration would be all plumbing on outside wall, with utility sink on middle of wall, then about 5 feet to the right would be 5'x5' half bath with small vanity sink and then toilet. I want to avoid digging up too much of the concrete slab for DWV. My idea is to cut out about a 24"x6" hole where the toilet drain would be, install 3" toilet drain which would run below slab level towards outside wall , and then run a 3" vent stack from the toilet drain pipe up through a new framed 2x6 wall directly behind the toilet. Both the utility sink and the vanity sink would then drain into the 3" stack with all plumbing running above floor grade within the 2x6 wall. I would most likely use studor vents on the two sinks, and would like to use a 3" air admittance valve on the 3 " vent stack also to avoid having to run it up through my metal roof. I know that residential code calls for at least one main vent stack piped to open air... but in my proposed shop application I think it would work fine. Thoughts... comments... advice? Keep in mind that I am not talking about permits and inspections for this project. Thanks.

 

[Scooby074]

Your setup is very similar to what i have in my barn. It works excellent. Probably flushes better than the house!! (Might have something to do with the old style high flow toilet thats installed )

I have no stack, really. Just a single Air admittance valve on about a 4' tall "stack" 1.5 sink drain I know its not code\, but it works really well. Matter of fact i have a washing machine that dumps into the sink, and the sink level never rises above 2" or so when the machine dumps.

Sink and washing machine are on the end of about a 6-8' run of 1.5", sloped and mounted on the inside of an external wall. I always meant to frame a little knee wall to cover it, but never got around to it.

Everything is above the slab, except the main drain out from the toilet out to the tank. I had to chip up around a 1'-2' square to mount the toilet flange, then tunnelled from the outside (about 4-5'), under the slab to meet up with the elbow from the closet flange. The only concrete i had to pour was what was in the 1'-2' square around the flange.

 

[westbrooklawn]

Jason,

Thanks for the response... it sounds like your setup is identical to what I am trying to do, except I will only have to tunnel in about 2' from the outside.

 

[MarkV]

I am not a plumber but I am around a lot of remodels. Your set up sounds fine, my only question would be the 3" vent stack. You can down size that to 2" and be fine.

MarkV

 

[Ed1C]

I agree, 2 inch vent should be fine. Here is pic of the set up in my barn - obviously before the concrete was poured. The box to the side is for a small shower stall, but shares to the toilet drain. The sink is further down.

You can also see the toilet drain to vent stack is a little shorter than the usual 12 inch rough in. I used a 10 inch rough in as they do make toilets with this shorter distance now. American Standard and other brands offer them in 10, 12, or 14 inch rough in. I just mention this as it might reduce your concrete busting job just a little.

 

[CinderSchnauzer]

In your "man cave" in addition to the toilet, if you can find room, consider a urinal. Doesn't need one of those fancy pressure flush valves. A ball valve works fine. Hot water is nice - 10 gal electric. If shop not heated a baseboard heater with thermostat will take the chill off, if freezing in the winter is a concern.

 

[westbrooklawn]

Ed - Thanks for the picture. The only difference in my proposed setup is that the utility sink and bathroom sink would drain into the vertical stack (behind the toilet) at a location above the floor level as opposed to below slab like your setup. Hindsight tells me I should have planned this ahead of time and roughed the plumbing in before the slab was poored... but then we all know what they say about hindsight!

CinderSchnauzer - I have thought long and hard about installing a urinal, but just can't spare the room. One thing I will definitely go with is a "chair height" toilet... I love them in my new house. It just doesn't make sense to have to get up from a seated position where your knees are higher than your butt!

 

[Ed1C]

One thing I will definitely go with is a "chair height" toilet... I love them in my new house. It just doesn't make sense to have to get up from a seated position where your knees are higher than your butt!

Even if you really don't need it now, someday we all will. Right height or ADA is the only way to go

 

[hitekcountry]

There are toilets the have the drain toward the back so you don't need to mess with the floor. They are a bit pricey though. I don't remember how much, It's been awhile since I checked.

 

[valley]

You can cut the floor with a dimond wheel, just wide enough to run your ABS then the floor is easy to concrete. I've done a lot of them with the vaves you are talking about, Never on the 3". I might rather vent out the wall just below the eve with a 90 degree ABS pointing down outside the wall on a job that will not be inspected. I think i understood you to say you are away from the outside wall where you would build your tree? In that case you need only a 6" wide by 16" slot in the floor to the new wall the rest of the trench will be undet the wall you will build to the outside wall. Good luck with the project.
Just reread your post, everything is on the outside wall. you just need a 6" slot in the floor through to the outside and your tree is above the floor.