I've built an addition that runs right over the 4 inch waste line to my septic system. I want to tie into it with 1 and 1/2 bathrooms. This image shows what I am thinking of doing. I've owned this hundred year old home for 20 years and have replaced all the old cast plumbing, so I'm comfortable with working with PVC.
My first question:
Am I nuts to do this myself?


I want to make sure everything drains well and is properly vented, and I've done a lot of research. I just don't know if I need all the vents I'm looking at doing. The 3" vent through the roof is already in place, just not connected to anything yet. And I know that the 2" vents are probably oversized but I already have that from another project. So my second question is can I remove any of the connecting vents (A, B, C, D)? I'm thinking B & D are not necessary.

Thanks in advance for the help.
Grace & Peace,
Steve



Edited 2 times.

no, you are not nuts for wanting to do this yourself.
but, you are wise to ask for help.
eliminate vent B.
tie sink 1 and sink 2 into the toilet drain in their respective baths.
keep both sink drains and vents 2 inch.
tie the shower and the washer separately into the black line drain and vent the shower.
ideally the washer drain can go into the vertical black line stack then it will be stack vented. if not then make the laundry trap/vent look like the sink trap/vent.

Ok that makes sense. Thank you again.

Grace & Peace,
Steve

I don't think you are nuts for wanting to take on this project. More like brave and not lazy.

Not too many people can just go from their regular job and then become a plumber and go rough in a bathroom.
But there are those that can and do. These people are on the upper end of the mechanical curve.

For me approaching about 20,000 hours in the trade it still makes me a bit uneasy to say yes I can rough
in a bathroom for you to code, leak free and problem free without a lot of sacrifice, blood, sweat and tears.
and still be friends at the end. haha. Plumbing can be a real challenge but the rewards are awesome like a
nice new modern bathroom. Good luck to you on your project.

NP16 , i started plumbing in the 60's and opened my own business in the early 70's.
don't even know how many hours i have put in ???
my only regrets are my knees and back have seen better days.

quote; For me approaching about 20,000 hours in the trade it still makes me a bit uneasy to say yes I can rough
in a bathroom for you to code, leak free and problem free

I hope that is hyperbole, because that would be about 10 years, and unless you were only trained to do sewers or service work, you had better be able to do it.

Thanks for the encouragement. Like I said the house is 100 years old and had all brass supply lines (and I think the original guy got paid by the foot) and Cast/steel waste lines. I have in the 20 years I've owned the home replaced all the existing plumbing, stripped out all the old plaster and rewired the whole house (old knob & tube). Sometimes I think I'm a General Contractor.

Packy, I am curious to learn from one of your recommendations which is to eliminate vent B.

Since both sinks and both WCs are stack vented, what would be the advantage to eliminate vent B and keeping A & C, versus keeping B and eliminate vents A & Cs as long as the sinks'trap arms are shorter than code required max? Isn't that configuration very similar to one bathroom with his & her sinks, and one WC plus one bidet? Is it mostly because there are two separate bathrooms hence each bath group need it's own dedicated vent?

sink 1 and sink 2 can not vent thru B. that would put the trap higher than the vent.
there is always a possibility that any fixtures upstream from the toilets can syphon the toilets when they drain.
so, wet vent the toilets thru the sinks and eliminate that possibility. also B becomes redundant as each toilet is now wet vented.
cabeesh ???

Yes I got it. Didn't catch the sinks are tying in low.

However, I assume ABC is a wall, so if sinks A and B drains do not run vertically down, but instead run horizontal towards B and tie into B via a double fixture fitting or two stacked sanitary tees, then B can stay and A and C will be unnecessary?

you still have toilet 1 flushing past toilet 2.
[www.plbg.com]

Sink. at 7', is too far from "B" for a "dirty arm".

hj I thought a 2" drain at 1/4" per foot can barely make it at 8' technically? I do agree it's not good practice to push the boundary.

packy, I got it now the best approach is to keep vents A & C, get rid of B.

To do it the way I was thinking, the two WC will have to be connected via a double fixture fitting (or back to back fitting) which is a hard to find fitting and difficult to snake without the snake bouncing across to the other side. Not to mention I will need to use long dirty arms, and in general, if the wall is standard 2X4, running 2" sink trap arms means cutting out most of the meat from the studs from both directions. Bottom line, bad idea. Thank you.

yeah, 2 inch at 1/4 inch pitch is 8 inches.. BUT there has to be air ontop of the water.

here, they do NOT use the 'theoretical" length. It is 42" for 1 1/2", 60" for 2", and 10' for 3".