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Help with new drain/vent/waste system

1536 Views 13 Replies 5 Participants Last post by  MushCreek
I'm currently building my own house (HEAVY into DIY!) and have a few DVW questions. Mostly, I'm having trouble trying to figure out where to put clean-outs. According to the books, you should have one on the high end of every horizontal run. That will be a lot of clean-outs! What about areas where it's hard to fit one in? I have a 3" run draining two toilets that I would like to run through the floor joists. The problem comes with the clean-out. They call for 18" of clearance for a 3" clean-out, but the joists are only 16" apart. Can I drill a hole in the next joist for access? Theoretically, it's more than 18" clearance, but you'd have to bend the snake up between the joists. I'm not sure if an inspector would buy that. The only other option for this run would be to drop the 3" run below the joists- something I'd rather not do with an eye to finishing the basement someday.

The next issue is 3 fixtures in close proximity- a washing machine standpipe, a lavatory, and a shower. According to the charts, that's too much for a 2" drain. Should I combine them into a single 3" pipe, or run two separate 2" pipes?

Lastly- Does it matter whether a vent is 'upstream' or 'downstream' of a fixture? For example, I want to put the vent for a toilet in the wall behind it. This is 15" downstream, towards the main drain. It would be nearly impossible to place it upstream of the toilet. I don't think it matters, but can't find any reference to this.

Any help on these questions would be most appreciated. This all looked easy at first, but is quickly becoming complex. Our local inspectors aren't very helpful (or strict) but I want it to function well. Thanks!
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Which code are working under?
Here's some UPC rules-
Clean outs at the base of stacks
Clean outs after 135 degrees(90 & 45) on horizontal runs
Horizontal runs under 5ft- clean outs not needed except sinks & urinals
**Except the bldg drain and its horizontal branches- a cleanout is not required above the floor level of the lowest floor of the building
An approved cleanout is needed where the building drain exits the building

A cleanout may be extended in height by using approved drainage fittings- in your example, bring 3" up through the floor for the cleanout. But you probably don't need that clean out anyways. If you do- you can use the toilet vent if piped properly
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Here's a sketch of the area in question. The horizontal section of 3" is the one that could run through the joists, if I can fit it in. The branch going up in the pic services the washer standpipe, the lavatory, and the shower. I transitioned to 3", as 2" is not enough for the three fixtures (I don't think). The vent locations shown are laid out to fit interior walls. I can run a vent up an exterior wall, but the house is ICF, which means cutting a channel in the foam. 'WC' is a toilet, 'V' is a vent. The little arrows show proposed clean-outs.The funky 45 degree angles on the left are to work around a wall, and is under the stairwell. The main line with the two toilets would run through the joists or just under them, then drop down about 5', with the elbow having a 2" outlet for a vent, and then transition back to horizontal through the 45 degree angle, and then back in line with the main stack through another 45. I don't think I'll have enough space in the joists anyway, as I have the 3" branch coming in, which also has to have enough drop. The main 3" is about 12' long, and the 3" branch is about 8' long.

I would love to give you some help. But I don't know what code you work with and I have a hard time understanding your drawing. Per UPC- you're all messed up. Very little of your venting is correct. I suggest reading up on venting or as suggested, hire some qualified help
I don't know IRC, I believe there are some plumbers here that do though.
What I can tell you per my code is that vents belong on the branch or fixture trap arm- not the building drain. Perhaps a IRC guy will chime in
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