Hi, Great website. I am a newie here seeking some help on a proposed DWV sys. For a small cabin I am in the process of building. The septic sys. Is already installed as is a 4" vertical vent stack. My design is a basic drawing of what I had in mind. All branch fixture drain lines will be no longer than 48" to the main waste drain line. The distance from the vent stack to each branch fixture is:
LAV. ~32"
WC ~78"
TUB ~84"
KIT. SINK ~96"

Will this layout fly, if so then I'll figure out the traps & fitting types, etc. Any ideas, comments, suggestions would be greatly appreciate. Sonny

OK! The lav can tie direct to the vent stack with a sanitary tee provided there's nothing draining above it. The tub will have to have a wye or combination wye and eighth bend rolled up on a 45 degree angle just after the tub trap for a vent. This vent to run through the roof or revent back to the vent stack at least 6" over the rim of the lavatory. Your toilet's OK. The kitchen will have its own vent and can tie back to the tub vent or revent back to the vent stack. Does this answer your question? Regards, Tom

Hi. Thanks for the quick reply. I tried to send a drawing with my post but I see it appears it did not go through. Must have done something wrong. I'll try again. Thanks. Sonny

Hope this drawing get through. Might explain my DWV sys. A little better. Sonny

Works for me. Check to see if the toilet vent's necessary or if the wet vent by the lavatory will be OK. Some areas do not allow wet vents. I would increase the sink drain, vent and stubout to 2". Next year I believe code's going to a three inch branch for kitchen sinks.due to disposals and the amount of garbage they produce so if you plan on a disposal now's the time to set up for the change. If not I would still go to 2 inch. Good luck, Tom

Thank you Speedball 1 for your help, much appreciated! On my original message I gave the wrong messurement for the Kit. Sink, its not 96" (that distance was from the tub). It's almost 15' from the stack to the kit. Sink. Will that be a problem? Other than maybe not needing a WC vent, are there any other ways to simifity this installation? Would a AAV be an option for the kit. Sink instead of running a 8' vent pipe to connect up to the tub vent?Sonny

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Would a AAV be an option for the kit. Sink instead of running a 8' vent pipe to connect up to the tub vent?

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If a permit will be pulled, check your local codes. If the work won't be imspected then justinstall the AAV where it can be serviced.

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On my original message I gave the wrong messurement for the Kit. Sink, its not 96" (that distance was from the tub). It's almost 15' from the stack to the kit. Sink. Will that be a problem?

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No problem as long as the sink's vented. Good luck, tom

Hi again. Since posting my original question I have been reviewing many of the plumbing questions from this site pertaining to DWV sys. Design. Very informative stuff! I came across a particularly interesting query posted Feb. 13-08 by CPOTTS454. His 1st. Floor DWV layout looks pretty much to what I had planned, except my plan (option#1) has a re-vent. I don't want to cut corners, but could my DWC layout #2 plan work as I got it laid out, thus elminating the re-vent and saving a lot of work running a vent line along a exterior wall. I would have a 2" drain for the lav., tub and kit. sink. The WC would be a 3" drain. The kit. Sink, I would vent with a AAV unit. I suppose this would be considered a wet vent/waste sys. One concern I would have with the AAV, is that it would be the closest fixture to the septic tank (~10' away). Any thoughts on this? Thanks again for all you help. Sonny

Hi. I am posting another request for some of you plumber experts out there. Could you please check out my previous queries concerning possible options for my DWV sys. I am wondering if option #2 of the previous query would work? Thanks. Sonny

Hi sonny:

Sorry Sonny, you need to add that vent back at the tub drain line... and I would not install AAV at the tub. Run the vent. Then you should be all set.

The AAV within 10 feet of septic should not be an issue.

If this helped, please RATE THIS ANSWER.. Thank you... Mark.

Good morning Sonny, Mark's correct! In drawing # 2 you are discharging a major fixture,( your toilet) past a unvented minor one ,(your tub) and that's a no-no. Vent the tub. The WC will be wet vented by the lavatory vent,(the extra vent off the lav in #1 iand #2 is not necessary) I don't approve of installing a AAV unless you absolutely can't run a regular vent. The reason being that AAVs are mechanical and anything with moving parts can fail. You vented the kitchen sink at first. What changed? Regards, Tom

Thanks guys, appreicate all your help! Ok, here's what I plan on doing.
* Run a 2" re-vent line from the kit. sink to the vertical vent stack
* Tie-in the tub/shower to the above re-vent line.
* No additional vent line for WC and Lav.
* Connect all branch fixtures to the main waste/drain line using wye fittings.

Question:
1. Should all branch fixture lines be connected to the horizontal waste/drain line on a eighth bend rolled up on a 45 degree angle?

2. Should the tub/shower vent be located on the 2" branch line between the P trap and the main horizontal drain line? Sonny

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Question:
1. Should all branch fixture lines be connected to the horizontal waste/drain line on a eighth bend rolled up on a 45 degree angle?

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Not by any code book I ever read. I think you may be confusing a dry vent coming off the main. You must roll up a fitting above the centerline to take off a dry vent. You tie to the main using a wye or a combo,(wye and eighth bend).to connect a branch.

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2. Should the tub/shower vent be located on the 2" branch line between the P trap and the main horizontal drain line?

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Yes. It goes like this. Tub drain, trap, vent and the main. The vent will always install downstream from the trap. Good luck, Tom

Good morning! On my last query, I am not sure I understand the answer to question #1. I am a little confused on how to connect my branch drains, particularly the WC to the main waste line. Let me rephase my original question.

* How should the individual branch fixture drains be connected to the main waste horizontal line as it pertains to my drawing? Do I connect on the side or from the top? Does it matter? Thanks. Onny

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Originally Posted by pvsonny

Good morning! On my last query, I am not sure I understand the answer to question #1. I am a little confused on how to connect my branch drains, particularly the WC to the main waste line. Let me rephase my original question.

* How should the individual branch fixture drains be connected to the main waste horizontal line as it pertains to my drawing? Do I connect on the side or from the top? Does it matter? Thanks. Onny

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1. Should all branch fixture lines be connected to the horizontal waste/drain line on a eighth bend rolled up on a 45 degree angle?

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NO!! You tie to the main using a wye or a combo,(wye and eighth bend).. And these fittings are connected flat with 1/4 inch to the foot to the foot slope at the branch of the fitting being used. The only time you must roll up a fitting above the centerline would be to take off a dry vent.

Rergards, Tom

Thanks Tom. A plumber I am not, so I do much appreciate all your help! Sonny