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Old 11-18-2010, 01:17 PM   #1
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Plumbing - DWV - Layout Diagram

First, thanks in advance to all that read this post and provide any input.

Well, renovation of plumbing is in progress and I wanted to ask for some advise from those that are much more experienced.

I've attached a diagram for a new plumbing layout of the DWV system. Currently it is all Cast Iron (CI) or galvanized pipe, but will be 90% replaced with ABS PVC.

House is in WA state, so UPC is the code guidelines.

Of course, code is a concern, but since all of these changes are primarily direct-replacement of existing piping, my belief is that new code compliance not a requirement, just a recommendation. However, I would like to hear anything not in compliance and any suggestions for improvements.

I've had no major problems, except for 1 leak, but I think it's time the exiting piping is replaced, and possibly tightened up (better hidden between floor joists and along/inside walls). Furthermore, the kitchen drain was not done incorrectly (piped into cleanout) and needs to be corrected (shown corrected in diagram).

So, first - any issues/concerns with the diagram?

Next, here's a few questions:

a) Can 1 & 2 be combined into a "1/4 Bend". I believe this would be shorted in depth (and fewer connections)?
b) Repeated questions from (a) for bends 7 & 8 ? 15 & 16 ?
c) Can the top air vents be combined within the attic space, creating only a single roof penetration ? What would be the minimum/max/recommended size of the combined pipe penetration?
d) How much would the size from question c change with the addition of a single attic AAV ?
e) Any critical distances that I need to be aware of?
f) Could 10 be swapped for a Double Sanitary Tee (removing 9 & 14) in order to shorten vertical distances ?

Again, Thanks for your time.
Attached Files
File Type: pdf Untitled.pdf (57.0 KB, 620 views)


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Old 11-18-2010, 04:52 PM   #2
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A) It can be a long sweep 1/4 bend, but not a normal 1/4 bend.
B) Unless impossible keep 2" running all the way to your kitchen sink. Then use a bushing fitting to reduce to 1.5" on your sanitary T.
C)yes they can, keep a 1/4" pitch on it going up. You can probably stick with 2" for your vent, but to be safe make it 3", and change #12 to a 3" Combo.
D) Don't know that answer
E) I don't see anything on your diagram that would make you concerned about venting problems. Horizontal runs for waste can only be so far with different pipes, but it looks like you have that covered.
F) Double san. Tee's are not always a good idea when you have to snake your system. That being said I would get rid of #10 and put in 2 3x2 combination wyes.


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Old 11-18-2010, 08:47 PM   #3
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A few things that I want to point out. Some of the items are code and some are personal preference. I use the UPC also but it varies a little according to areas.
1. You have a horizontal wet vent on top of the tub. (pipe between points 2 & 3) Not allowed here, plus minimum size wet vent is 2" so your vertical lav line should be 2"
2. use long sweep 90s instead of 2 45s though both are leagal
3. bathtub/shower units may be 1.5" but shower only must be 2"
4. Fitting #5 must be a sanitary tee
5. Kitchen sink needs a clean out
6. Kit sink can vent on 1.5"
I can't use AAV so I can't help you there.
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Old 11-18-2010, 09:06 PM   #4
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looks pretty good, other than the things already said. keep in mind code is not a huge deal on existing work, but as soon as you cut it all out it must be done properly. don't just follow the old stuff. combining vents in the attic is not a big deal, as long as 1/3 or less of the vent is horizontal. if it's more than that, upsize to the next size up to fix it, and grade it back toward the fixture at 1/4" per foot. don't use the aav, washington doesn't allow them and plus you're already in the attic how hard is it to push it out the roof?
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Old 11-19-2010, 09:07 PM   #5
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one thing is (although not too certain with your area, i am from jersey) in my area youneed at leat one 3" vent going through roof. again not too sure about your area
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advise , diagram , dwv , upc

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