Feedback on DIY plumbing plans for new Master Bathroom

[Beau G]

Hi everyone,

New forum member and DIY'er here with no formal plumbing training. I'm up to my eyeballs with renovations of our home in Santa Barbara, CA and the next project up is an addition that will become our new master bathroom. I'm hoping to save some $ and gain some new skills by designing and installing the plumbing system for this new bathroom. I've done a lot of research online (plumbing codes, forums, YouTube, etc.) and have attempted to layout a DWV plan for this project. We are governed by the 2019 California Plumbing code, which is based on the 2018 UPC and I've done my best to adhere to these requirements. I'm hoping that some seasoned plumbers here can review my work to confirm I've got a viable plan and offer any feedback for optimization.

Floor plans and some plumbing diagrams are attached.

Thanks in advance!
-Beau

 

[wwhitney]

A few comments:

- CA is now on the 2022 CPC which is based on the 2021 UPC.

- Running drain lines directly under walls is not necessarily a plus, although passing under a wall is a plus for a dry vent takeoff.

- The 1-1/2" tub trap arm is limited to 42" under the UPC. If you need more length, you can use a 2" trap and 2" trap arm, then it can go 60". Note that if you use any slip joist connections in the tub waste and overflow, they need to remain accessible; if you want to seal everything behind drywall, use glue joint connections.

- The cross where the two lavs join should be a 2x1.5x1.5x1.5 double fixture fitting. A cleanout below that fitting is a good idea, as it can be hard to snake through a double fixture fitting and end up going down rather than across to the other lav.

- Your plan is OK for dry venting everything, but you do show some fittings that don't exist. Namely at the WC, shower and tub vent takeoffs, you effectively show a combo with "combo" side entry for the vent takeoff. [Vent takeoffs have to be of a drainage pattern, so those fittings with a straight side inlet can't be used.]

So you'll need to move your vent takeoffs to before or after the "tee" connectivity of the horizontal combo. And for the case of the shower, it has to be before (towards the shower); for the tub and the WC, the combo is just used for a cleanout, so it can be after. Each vent takeoff also needs to be within one pipe diameter of fall from the trap outlet.

- You could reduce the dry vent takeoffs by using some wet venting. An obvious minor tweak to the routing would be to dry vent the shower with a 2" dry vent, and then use it to wet vent the WC. That way the WC line doesn't have to run perpendicular to the joists at all.

- The tub drain after the vent only needs to be 2", not 3", so you could economize there. That 3" "main line" is running perpendicular to your joists, so it would either need to be below the joists, or you'd need 2x12 joists to comply with the prescriptive rules for holes in joists (make 1/3 joist depth, with 2" clear vertically from top and bottom of joist), and then you'd still be limited to 14' of run through the joists (based on the highest joist hole being 2" from the top, the lowest being 2" from the bottom, and an 11.25" height for a 2x12).

- You could also dry vent the tub with a 2" dry vent, use its drain to wet vent the shower (send the shower drain parallel to the joists rather than perpendicular), then use the combined drain (can still be 2") to wet vent the WC. The restriction is that the WC vent has to be within 6' of pipe run (measured along the axis of each piece of pipe) from the closet flange, so the left-right on the page tub drain might need to move closer to the WC, not clear.

Cheers, Wayne

 

[Sponsor]

 

[Beau G]

A few comments:

- CA is now on the 2022 CPC which is based on the 2021 UPC.

- Running drain lines directly under walls is not necessarily a plus, although passing under a wall is a plus for a dry vent takeoff.

- The 1-1/2" tub trap arm is limited to 42" under the UPC. If you need more length, you can use a 2" trap and 2" trap arm, then it can go 60". Note that if you use any slip joist connections in the tub waste and overflow, they need to remain accessible; if you want to seal everything behind drywall, use glue joint connections.

- The cross where the two lavs join should be a 2x1.5x1.5x1.5 double fixture fitting. A cleanout below that fitting is a good idea, as it can be hard to snake through a double fixture fitting and end up going down rather than across to the other lav.

- Your plan is OK for dry venting everything, but you do show some fittings that don't exist. Namely at the WC, shower and tub vent takeoffs, you effectively show a combo with "combo" side entry for the vent takeoff. [Vent takeoffs have to be of a drainage pattern, so those fittings with a straight side inlet can't be used.]

So you'll need to move your vent takeoffs to before or after the "tee" connectivity of the horizontal combo. And for the case of the shower, it has to be before (towards the shower); for the tub and the WC, the combo is just used for a cleanout, so it can be after. Each vent takeoff also needs to be within one pipe diameter of fall from the trap outlet.

- You could reduce the dry vent takeoffs by using some wet venting. An obvious minor tweak to the routing would be to dry vent the shower with a 2" dry vent, and then use it to wet vent the WC. That way the WC line doesn't have to run perpendicular to the joists at all.

- The tub drain after the vent only needs to be 2", not 3", so you could economize there. That 3" "main line" is running perpendicular to your joists, so it would either need to be below the joists, or you'd need 2x12 joists to comply with the prescriptive rules for holes in joists (make 1/3 joist depth, with 2" clear vertically from top and bottom of joist), and then you'd still be limited to 14' of run through the joists (based on the highest joist hole being 2" from the top, the lowest being 2" from the bottom, and an 11.25" height for a 2x12).

- You could also dry vent the tub with a 2" dry vent, use its drain to wet vent the shower (send the shower drain parallel to the joists rather than perpendicular), then use the combined drain (can still be 2") to wet vent the WC. The restriction is that the WC vent has to be within 6' of pipe run (measured along the axis of each piece of pipe) from the closet flange, so the left-right on the page tub drain might need to move closer to the WC, not clear.

Cheers, Wayne

Wayne,

Thank you so much for the detailed advice. I'll digest some of this and update my plans accordingly.

To your point on notching joists, this bathroom is at the FAR opposite end of the house from where the main waste line exits the home, so I'll definitely need to gain some elevation by the time I hit this bathroom. Thankfully, a framer buddy had some engineered I-joists laying around that I plan to use for this project. They are 12" tall with 1-1/2" thick lumber at top and bottom with approx. 9" of engineered plywood to play with in between. I'll need to look up hole/notching imitations but I'd guess that I should have more wiggle room than solid lumber joists. Transitioning from the home's solid joists (and over/through the foundation wall) to the addition's I-joists may be a challenge.

Thanks again,
Beau

 

[Jeff H Young]

As a last or near last resort a new 3 inch line could run to other side of house and tie into main drain on the far end if the existing was too high and had fast fall on the upper end.
Beau did you apply for building permit in 2022 or 23 ? Just trying to understand how or why you would be 2019 cpc to determine the plumbing code we are using not that it changes any of this work but for me for other jobs
A minor detail here on Truss joists might be a little taller than the 11.5 std joists if the floor height is important to match

 

[Beau G]

As a last or near last resort a new 3 inch line could run to other side of house and tie into main drain on the far end if the existing was too high and had fast fall on the upper end.
Beau did you apply for building permit in 2022 or 23 ? Just trying to understand how or why you would be 2019 cpc to determine the plumbing code we are using not that it changes any of this work but for me for other jobs
A minor detail here on Truss joists might be a little taller than the 11.5 std joists if the floor height is important to match

Hi Jeff,

Thanks for the ideas to manage elevation change. I haven’t yet applied for a building permit, so the codes that I was referencing were just what I found online. I must be looking at outdated information. Regardless, I don’t think(?) there are any meaningful changes that will impact my design here.

On the truss joists, I actually already have them on hand. From what I recall, they are just a hair under 12”.

Thanks,
Beau

 

[Jeff H Young]

I dont know of codes changes affecting you Im just never sure when they change , . Ive had a rescent discussion elsewhere in regards to which plumbing code we are following All I know is how I read it, and have some other opinions I might just call my city inspector but havent
As for the joist height Im not a framer but I think you want your foundation wall 3/8 lower on the addition, than the conventionaly framed portion of cource you gotta think about the sheeting thickness I suppose

 

[Beau G]

A few comments:

- CA is now on the 2022 CPC which is based on the 2021 UPC.

- Running drain lines directly under walls is not necessarily a plus, although passing under a wall is a plus for a dry vent takeoff.

- The 1-1/2" tub trap arm is limited to 42" under the UPC. If you need more length, you can use a 2" trap and 2" trap arm, then it can go 60". Note that if you use any slip joist connections in the tub waste and overflow, they need to remain accessible; if you want to seal everything behind drywall, use glue joint connections.

- The cross where the two lavs join should be a 2x1.5x1.5x1.5 double fixture fitting. A cleanout below that fitting is a good idea, as it can be hard to snake through a double fixture fitting and end up going down rather than across to the other lav.

- Your plan is OK for dry venting everything, but you do show some fittings that don't exist. Namely at the WC, shower and tub vent takeoffs, you effectively show a combo with "combo" side entry for the vent takeoff. [Vent takeoffs have to be of a drainage pattern, so those fittings with a straight side inlet can't be used.]

So you'll need to move your vent takeoffs to before or after the "tee" connectivity of the horizontal combo. And for the case of the shower, it has to be before (towards the shower); for the tub and the WC, the combo is just used for a cleanout, so it can be after. Each vent takeoff also needs to be within one pipe diameter of fall from the trap outlet.

- You could reduce the dry vent takeoffs by using some wet venting. An obvious minor tweak to the routing would be to dry vent the shower with a 2" dry vent, and then use it to wet vent the WC. That way the WC line doesn't have to run perpendicular to the joists at all.

- The tub drain after the vent only needs to be 2", not 3", so you could economize there. That 3" "main line" is running perpendicular to your joists, so it would either need to be below the joists, or you'd need 2x12 joists to comply with the prescriptive rules for holes in joists (make 1/3 joist depth, with 2" clear vertically from top and bottom of joist), and then you'd still be limited to 14' of run through the joists (based on the highest joist hole being 2" from the top, the lowest being 2" from the bottom, and an 11.25" height for a 2x12).

- You could also dry vent the tub with a 2" dry vent, use its drain to wet vent the shower (send the shower drain parallel to the joists rather than perpendicular), then use the combined drain (can still be 2") to wet vent the WC. The restriction is that the WC vent has to be within 6' of pipe run (measured along the axis of each piece of pipe) from the closet flange, so the left-right on the page tub drain might need to move closer to the WC, not clear.

Cheers, Wayne

Wayne,

I made some adjustments based on your feedback. Updated plans are attached.

Changes include:
- Offset the vents from the horizontal drain "tees" (can you confirm if I interpreted your guidance on the shower vent location correctly?)
- Called out fitting on double lav "cross" and added a cleanout to drain below trap
- Took your advice of went venting the WC using the 2" dry vent for the shower (again, can you confirm I've interpreted this correctly?)
- Downsized the "Main 3" branch line" to 2" upstream of the WC drain. Your post mentioned downsizing this drain "after the tub vent". Does the "main drain" and cleanout upstream of the tub vent need to be 3" to accommodate a full size cleanout?

I may consider wet venting both the WC and shower through a 2" tub vent, however, I'll need to make some more precise pipe length estimates. I don't know if I can get that vent within 6' of the closet flange for the WC. I may hold off on that optimization for now.
Lastly, is there any concerns with tying the 1.5" lav vent into the 2" shower/WC vent in the attic and having a single 2" roof penetration? Or even tying in the tub vent too for a single roof penetration? I'm looking to minimize holes in the roof and potential leak points.

Again, I greatly appreciate your help here!

Beau

 

[wwhitney]

1) Yes, the shower vent location is good. Note that when determining the tub trap arm length, it extends all the way to the vent takeoff.

2) Yes, the WC wet vent is good. Note that the 6' length limit is from the closet flange to the wye or combo where the 2" shower drain joins the 3" WC line.

3) No, you can't upsize the clean-out stub. I referred to "after the tub vent" just because the sizing rules for tubs drains are a little weird: you can use 1-1/2" for the trap arm (up to the vent), but after the vent any horizontal drain carrying the tub has to be 2". So upstream of the vent takeoff you could have all 1-1/2", although with the 2" cleanout having the short section of 2" drain makes sense.

4) On wet venting everything via the tub, that "main line" can move towards the WC. Then the tub vent takeoff occurs before the tub drain turns ninety degrees, and the shower trap arm goes perpendicular to the "main line" to join it before the WC joins the "main line".

5) You can combine all the dry vent takeoffs into a single new 2" roof penetration. This assumes your existing roof penetrations already comply with the "minimum aggregate vent area through the roof" rule in UPC 904.1. That requires the equivalent area of a 3" vent for most houses with up to 5 WCs, and the equivalent area of a 4" vent for houses with 6 or more WCs. 3" area equivalent would be one 3" vent through the roof, or (2) 2" vents plus a (1) 1.5" vent.

Cheers, Wayne

 

[Beau G]

1) Yes, the shower vent location is good. Note that when determining the tub trap arm length, it extends all the way to the vent takeoff.

2) Yes, the WC wet vent is good. Note that the 6' length limit is from the closet flange to the wye or combo where the 2" shower drain joins the 3" WC line.

3) No, you can't upsize the clean-out stub. I referred to "after the tub vent" just because the sizing rules for tubs drains are a little weird: you can use 1-1/2" for the trap arm (up to the vent), but after the vent any horizontal drain carrying the tub has to be 2". So upstream of the vent takeoff you could have all 1-1/2", although with the 2" cleanout having the short section of 2" drain makes sense.

4) On wet venting everything via the tub, that "main line" can move towards the WC. Then the tub vent takeoff occurs before the tub drain turns ninety degrees, and the shower trap arm goes perpendicular to the "main line" to join it before the WC joins the "main line".

5) You can combine all the dry vent takeoffs into a single new 2" roof penetration. This assumes your existing roof penetrations already comply with the "minimum aggregate vent area through the roof" rule in UPC 904.1. That requires the equivalent area of a 3" vent for most houses with up to 5 WCs, and the equivalent area of a 4" vent for houses with 6 or more WCs. 3" area equivalent would be one 3" vent through the roof, or (2) 2" vents plus a (1) 1.5" vent.

Cheers, Wayne

Wayne,

Again, tremendously helpful guidance here. Thank you. I've got plans version 3 (w/ WC wet vented through shower vent) and version 4 (with WC and shower wet vented through tub vent) attached. I'm still not sure if I can meet the maximum trap-to-vent distances for version 4, but I'll continue to explore. Regardless, I think I understand the concept and can decide between Ver 3 and 4 after some more detailed planning and measuring.

One change I made in version 4 was to upsize the "main drain" to 3" between the WC trap arm "combo" and the tub vent, according to a CA plumbing code reference I found for wet venting, "The wet vent shall be not less than 2 inches (50 mm) in diameter for 4 drainage fixture units (dfu) or less, and not less than 3 inches (80 mm) in diameter for 5 dfu or more." I'll have 6 DFU between the shower (dual heads) and WC, so I believe I'll need a 3" wet vent. Can you confirm if the dry portion of the vent can still be 2"?

I'll still need to verify that I can meet the aggregate venting requirements, but that's a simple enough change to accommodate if needed.

Please let me know if you see any other lingering issues in these Ver 3 and Ver 4 plans.

Thanks,
Beau

 

[wwhitney]

One change I made in version 4 was to upsize the "main drain" to 3" between the WC trap arm "combo" and the tub vent, according to a CA plumbing code reference I found for wet venting, "The wet vent shall be not less than 2 inches (50 mm) in diameter for 4 drainage fixture units (dfu) or less, and not less than 3 inches (80 mm) in diameter for 5 dfu or more." I'll have 6 DFU between the shower (dual heads) and WC, so I believe I'll need a 3" wet vent. Can you confirm if the dry portion of the vent can still be 2"?

On the last question, certainly.

As to the multiple showerheads, it is true that the California Plumbing Code assigns an additional DFU for each shower head beyond the first, so a 2 showerhead shower is 3 DFUs. So as a tub is 2 DFUS, that makes 5 DFUs together, and the wet vent would need to be 3". Good catch, I was assuming only one showerhead. But the increase in size to 3" would only apply to the portion of the wet vent carrying 3 DFUs, i.e. starting where the shower joins.

However, the California Green Building Code requires that each showerhead use at most 1.8 gpm, and that with multiple showerheads, either you use one shower valve that limits the total flow to 1.8 gpm, or if you use multiple shower valves, they are plumbed so that only one can be used at a time.

Chapter 4: Residential Mandatory Measures, California Green Building Code 2022 | UpCodes

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So I would suggest the shower still counts as a single showerhead and can be considered 2 DFUs, leaving you with only 4 DFUs and a 2" wet vent still suffices.

Both Ver3 and Ver4 look good.

Cheers, Wayne

 

[Jeff H Young]

I was thinking of version 4 with a change you need to provide a 3 inch clean out at the end Id extend past the tub vent . of cource the clean out has accesability requirements, The best way (if convieniant ) in my opinion is to extend to outside the building. cleanouts in crawlspace have to be withen so many feet of access hatch or opening. Cleanouts usually only get called by experianced inspectors most combo inspectors wont know or care if they did but its kinda major to have to correct
BTW, Beau , pretty unlikely the venting is that screwed up that adding a 2 inch vent wouldnt be sufficient . definately walk around the house and look thats pretty easy to check, Also take a close look at that 72 " inch note on your drawing regarding length to closet flange from the vent take off and how that is measured to be sure you comply.


Looking good!