I am building a bathroom on a slab and need to setup the waste lines before the concrete pour. I have enclosed a diagram showing the fixture placements, waste line size and distance to the main. First I would like to know if the 4" main line which runs across the room and vents to the roof can act as the vent for the toilet, sink and shower. From what I understand the washing machine and kitchen sink are too far from the main line for it to act as the vent so I would connect them directly to the roof vent. Any comments as to sizing, distance and placement would be greatly appreciated.

or
[s20.postimg.cc]

1. A sewer is NOT a "vent"
2. You cannot connect to the main line without first venting the fixture.

the way you have it drawn, you will need 5 separate vents.
3 lines with no vents and 2 lines appear to be vented below the slab (not to code)..
vents must be located higher than the trap it is venting.
you can vent into the 4 inch stack but you must tie in 6 inches above the overflow of the highest fixture it serves.

Your plumbing project really could benefit from a 30-60-90 triangle and a good isometric drawing. Horizontal runs will be lines at 30 degrees. Vertical line is vertical pipe. If you can draw it you can build it. Sizing is done by adding fixture units and then consulting a chart for drainage and venting pipe sizes.



Edited 1 times.

I did my best to update the drawing showing only the bathroom pieces. The sewer line vents to the roof and my three fixtures tie into that same sewer line vent (at least 6" above lav).



[s20.postimg.cc]

I have two questions regarding my second diagram.

1) does the sewer line need its own vent or can it be capped off after the shower and the fixtures get vented as shown?
2) Can the toilet vent be used as a wet vent for the lav drain?

I have a blank slate as I have not even dug the trenches yet. This will all be set under a slab so I would like to perfect it beforehand. Any tweaks or suggestions would be greatly appreciated.


[s20.postimg.cc]



Edited 1 times.

Your Shower vent needs to be rolled up on a 45 degree angle and then come up in the nearest wall to satisfy code in So Calif. Check with your Inspector.

your latest diagram shows the lav drain connects to the vertical riser part of the toilet drain?

If you wish to wet vent the toilet via the lav drain you should connect the lav drain to the horizontal toilet pipe with a wye fitting.

The shower as shown is a horizontal dry vent. If ever your main line backs up into the shower pipe and shower vent, once the pipe is cleared the debris may not clear from the vent branch as nothing is washing/rinsing that vent pipe. You may want to roll the vent connection up a bit, or try to design a wet vent system with all three fixtures, but the main pipe being in the middle causes complication in that it may necessitate a "round about loop".

I am not a pro so my comments may be off.

see if this makes sense..

pipe toilet straight to tank.
pull off vent for toilet and tie both shower and lav into it.
lav can be 5 feet away from vent and shower can be 6 feet away.
my code calls for a full size vent so the vent and its extension thru the roof would need to be 3 inch.

Thank you for posting the image. I uploaded my version of the drawing for the bathroom and added in the washing machine and kitchen sink. I wanted to ask two questions.

1) Am I ok with my connection placement that ties one drain to the other? I plan on using combo wye & 1/8.

2) other than the toilet leading out to the septic I was planning on using 2" pvc for the rest of the below grade piping. Is there any issue increasing to 3" pipe? My reasoning for the change is that it should allow me a slightly further distance from the trap to the vent. I read the max for 3" pipe is 12' from trap to vent. Does that number hold up for my sink, washer and shower or is it shorter?



[s20.postimg.cc]



Edited 3 times.