Drain, waste, and vent

[grover]

Drain, waste, and vent.  I'm not quite to that point yet but that doesn't stop me from worrying about it.  I am building on a crawl space and my waste line to my septic tank exits the house foundation on the left side and about 3-4 feet from the back corner which is where my bathroom is.  Going across the back of the house from left to right is bath with shower, toilet, sink.  The kitchen sink is next to the bath and has the last drain.  I have a utility room which sits just on the other side of the bathroom wall and toward the front of the house.  I thought I would just keep the main 3" drain line running parallel to the back wall and maintain that 3-4 foot distance from the back wall.  I don't have a problem with hooking the drain lines into that but I'm having trouble trying to figure out how to run my vents.  You can't run a horizontal vent under the floor so how will that work?  I've looked through Google images and most just show a main vent stack that the toilet drains into which would run in the back wall but I can't figure out how that would hook into my drain.  My entrance to the crawl space is on the back wall around about where the bathroom sink is if that matters.  It's probably simple but I can't picture it.

[Redoverfarm]

Is it possible to run the vent up through that partition between the bathroom and utility room.  Ideally partitions are the best place to run vent lines up through.   If it doesn't fall quite on top of your main you could use some 22's or 45's to bring it to your main.  Since your main is under the footing it seems you would have enough room to lower it some to make that odd angle work.     Of course without seeing what you have it is difficult to give a good answer or suggestion.

[grover]

Yes, I know.  Hard to explain and hard to draw in 3D.  Do you know the max distance that toilet drain can run before hitting the drain/vent stack?  Toilet is on the other side of the bath from the wall you mentioned.  In fact everything drains on the other side of the bath (outside wall)...except for the washer.

[MushCreek]

DWV was the single-most frustrating part of my build! It's really hard to get information. I have three different plumbing books, and they all differ on this. I even tried to get help on-line, and was stonewalled at every turn.

What I finally learned is that vents aren't there to vent the actual device that they are close to; they are there to protect the trap water from other devices in use. If you flush a toilet near a sink without a vent, for example, the rushing water creates a vacuum, and can suck the water out of the sink trap. The water in the trap keeps sewer gas out of the house, so you don't want this to happen! Basically, there has to be a vent between the device and the rest of the system.

If you look it up, or use a book, you will find charts stating how far a device can be from a vent, based upon the drain size. These range from 3' to 10', depending upon the pipe size and the local plumbing code. I wound up having a vent for each device, as it gets even more complicated using common vents and other tricks. One useful product is a Studer valve. or Air Admittance Valve. AAV's can be used in most areas, and are commonly used for things such as a sink in an island, where there is no other way to vent it. Most devices are on or near a wall where you can run the vent up to the attic. All of these vents can then be connected to one or more roof vents. Once you are 6" or more above the device flood level, the vents can be run horizontally.

You still need to have a main or stack vent from that main line. You'll need a 6" 'wet wall' to have enough room to get that to the attic. I can't really visualize what you are dealing with without at least a floor plan.

[Redoverfarm]

Just a word of caution when using Studor valves.  They require air to work so if it is enclosed into a air tight area such as a wall they will not work properly.  Sort of like trying to suck air out of a bottle.

[zion-diy]

not sure if what I did was kosher, but I simply placed my vent pipe where the septic line exits my house and heads for the tank. (to the right of tree in the pic) Has worked just fine since 2005 no odors or problems of any sort.




here is a blueprint of the layout.

[Davegmc]

I'm currently installing my DWV system. I'd hate to even hazard a guess how many hours I've spent researching this. The best little guide I've found describing all the rules is from the City of Camarillo, CA.

http://www.ci.camarillo.ca.us/docs/Drainage%20Piping.pdf

The best book I've found is Plumbing a House by Hemp.

Also if you go to Dave and Lisa's build in the owner-builder projects forum, he documented his DWV learning curve, very helpful
http://countryplans.com/smf/index.php?topic=3854.0

Dave