I'm building a barn with a bathroom in the front left hand corner of the building. The septic tank will be on the left side of the building also. A floor drain shower will be in the corner, followed by a sink and the toilet(all on the left wall) To the right of the shower on the front wall I want to place the washing machine drain. I need advice on how to do the under slab DWV layout. Thanks in advance for your help.

Tell you what TjP1:

I am off to work now... but will try to get back to this later tonight. Check back then.

Tom (speedball) may also pop in to get you started. I will see what I can come up with tonight. Chat then... MARK

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I'm building a barn with a bathroom in the front left hand corner of the building. The septic tank will be on the left side of the building also. A floor drain shower will be in the corner, followed by a sink and the the toilet(all on the left wall) To the right of the shower on the front wall I want to place the washing machine drain. I need advice on how to do the under slab DWV layout. Thanks in advance for your help.
OK! I'll stand infoe Massplumber until he gets back to you.
Most bathroom groups are roughed in like this. Make your toilet main at least 3" and everything else 2" althow you may drop the lavatory drain to 1 1/2" but I would still keep the vent at 2".
Toilet runs its own line to the septic tank. The Lavatory connects to toilet drain and runs a vent off the top the stubout tee.
The toilet wet vents through the lavatory vent and the shower connects to the lavatory drain and is wet vented by it although a floor drain does not need to be vented it's a good idea to wet vent it anyhow. Your washer will connect to the toilet drain under the slab and come out of the slab with a sanitary tee. The branch of the tee will tie into a trap with a 36" stand pipe and the run of the tee will go up as a vent and tie back to the lavatory vent and then out the roof. More questions? I'm as close as a click. Regards, Tom