Washington - DWV Layout Questions (UPC Code)

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NoCastIron

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Going through this because the bid we got from any local plumbers was over twice what we were expecting, so I'm buckling down and taking this on myself. I have no concerns over the actual work but want to ensure I've laid everything out properly.
  • Current DWV is all cast iron. I'm planning to replace with PVC. No particular reason for PVC over ABS, I just see PVC used by many and it's more readily available around here at big box stores
  • This branch is for a single guest bathroom sink and a single toilet
  • The drawing has 2" and 1 1/2" written for the sink branch (vent and drain); I plan to use 1 1/2" as I understand that's what is required by UPC and there is no need for 2"
  • IMPORTANT: I didn't draw this, but the current vent is directly above the sink vent line (opposite of what the drawing shows, don't ask why I drew it that way). If the incoming vent from the roof is 2" I'm guessing I can use a 2" x 1 1/2" x 2" sanitary tee so that the incoming vent is 2", the vent straight down to the sink is 1.5", and the vent going right towards the toilet is 2"?
  • I believe main line is a 3" cast iron but I need to verify
nocastiron-01.jpg


Appreciate any insight! I believe I have everything correct but want to ensure I do before proceeding
 
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wwhitney

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Looks good to me. A couple comments:

- For the 3x2x3 san-tee you need (which you show via a bushing in a 3" san-tee), you could use a low heel inlet quarter bend. That's basically the same as a san-tee.

- If you made the lav drain and vent 2", then you have the option to omit the WC vent and wet vent it via the lav. In which case it would probably be preferable to roll your 3" combo to horizontal (or use a horizontal wye instead), with the closet bend outlet pointing straight into it.

Cheers, Wayne
 

NoCastIron

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Thanks, Wayne, appreciate it!

The feedback on the low heel inlet quarter bend is good, saves me having to glue up one extra connection when using the bushing.

The wet vent option I didn’t do, partly because I’m not a plumber and it’s easier to understand a dry vent versus the nuances of a wet vent, and primarily due to the floor structure below this. About 6” to the right of the closet flange is a 4x8 support beam running on the Z-axis of this picture and the plumbing has to drop below that before it can go meet the main line out of the house (also running on the Z-axis)

edit: this doesn’t mean I couldn’t do away with the direct vent for the toilet portion and replace the sanitary tee with a 90, but I figure it’s worth a bit of extra effort to have a dedicated vent for the toilet just to ensure no issues. We have a Toto Ultramax II which as I understand is quite a quick flush
 
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