Shower vent question in bathroom remodel

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Vinmassaro

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I am currently renovating my master bath and am unsure if I need to add any additional venting for the shower, and where if required. Below is a diagram of how the plumbing is set up. Thank you.
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wwhitney

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If the "vent/drain" is meant to represent vertical pipe (a stack), and all the thin lines are horizontal drains:

Yes, for the IPC the shower is not vented in your diagram. You need to add a wet or dry vent to the shower drain within one pipe diameter of fall from the shower p-trap. So for a 2" drain with exactly 1/4" per foot fall, it can be up to 8' from the p-trap. The IPC allows a dry vent to be before or after the shower drain joins the WC, while a wet vent would have to join the shower drain before (upstream) of the shower/WC joint.

For a dry vent, the vent has to rise at least 45 degrees above level from the point of takeoff until 6" above the flood rim level of the associated fixture(s) (would include the WC if the vent takeoff is downstream of the shower/WC joint).

For a wet vent, you could reroute the lav drain; the vent would still go to the stack, but again rising until at least 6" above the lav flood rim before turning horizontal. Then the lav drain would join the shower drain to wet vent, within the limit previously mentioned.

Cheers, Wayne
 

Vinmassaro

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Hi Wayne, thanks for the reply. I think it will be helpful for me to understand if I post some photos later today so I can get a better idea of what the easiest way to do this would be. One question I'm wondering about is, I never noticed any issue using the shower previously. Under what condition would the lack of shower vent become a problem?
 

Vinmassaro

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Here are a couple photos to show where things are. The shower plumbing (recessed floor for Schluter curbless shower), the toilet, and sink and vent stack. What would be the easiest way to add a vent for the shower?


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wwhitney

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On those holes in the joists for the shower drain, do you have 2" of solid joist remaining above each hole? If it's less, then the joist needs reinforcing, as the hole location does meet the prescriptive limitations.

On venting, the shower drain is the only issue. The WC would be fine if the shower weren't there, as it is being wet vented by the lavs and there is not length limit (for the IPC) on the distance or fall from the closet flange to the vent. I see two options for venting the shower (which would then become the wet vent for the WC, since the WC hits the shower before the lavs):

1) If the wall with the lav stubouts has a wall underneath it, you could send the shower trap arm straight down the joist bay to that wall, use a san-tee to take off a vent there, which rises in the wall and then connects to the existing copper vent at least 6" above the lav flood rim. Then the drain needs to combine with your other drains in the wall below, which means opening up that wall.

2) Within the confines of the bathroom, you could do something like the marked up photo below. I show the u-bend pointing away from the wall with the lav stub outs to maximize space for the run parallel to the wall with the new vent drawn in--this may not be necessary. Then the trap outlet elbow points at the new vent wall at a 45 degree angle, and then hits a 45 to run parallel to it.

If you can easily get under the wall, then an upright combo (or san-tee on its back if space is tight) can be used for the vent takeoff. If you can't easily get under the wall, but can get just next to it, you use a wye that is rolled 45 degree off upright, plus a 60 to turn vertical into the wall (or a san-tee on its back rolled 45 degrees, plus a 45, if space is really tight). Then the vent has to rise in the wall to connect with the existing vent somehow, at least 6" above the lav flood rim. The drain hits a LT90 to connect to your existing run perpendicular to the joists.

Cheers, Wayne

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Vinmassaro

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I'm aware of the improper boring - unfortunately this bathroom was remodeled prior to me owning the home. I can't reinforce/sister the entire length of these joists because this is on a 2nd floor above a finished lower level, so the plumbing is where it is.

Here is are some other photos with the floor removed that show where things are currently placed. You can see I don't have much room based on where the plumbing is because of how the holes in the joists were bored. Can I come off the side of the long piece and run it under the trap and up through the wall? There is actually an unused roof vent pipe (1.5" copper) on this side that would be closer than running plumbing to the other side and connecting into the vent where the lavs are. Thanks!

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wwhitney

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Can I come off the side of the long piece and run it under the trap and up through the wall?
Probably not.

Measuring parallel to the joists, what is the distance from the shower trap inlet both to the face of the wall framing where you'd like the vent, and to the hole in the joist that the shower drain first goes through? And measuring vertically, what is the distance from a level plane that is just above the joists (so the top of the joists if they are all in plane and all level) to the top and bottom of that hole in that joist?

If you used a linear drain that was along one wall, rather than a center drain, then you'd have a much better chance of vent the shower drain up that wall.

It's worth mentioning an option for you to wet vent the shower. Right now, where you have two san-tees for the two lavs, side by side with their inlets pointing away from each other and the drains and vents recombined above and below, you could use one of the drains to wet vent the shower. You'd change the bottom wye to a 45 for the san-tee on the left. Then the san-tee on the right would hit a LT90, and the 1-1/2" drain could need to go through the studs to above the appropriate joist bay. Then a quarter bend to turn down, a LT90 to turn into the joist bay, and a horizontal 2x2x1-1/2 combo to join the shower drain while it is running perpendicular to the joists. You can pick whatever joist bay is convenient, as long as the total fall of the shower drain from the trap outlet to that combo which wet vents the shower is less than one pipe diameter, or 2" for the 2" shower drain.

Cheers, Wayne
 

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Wayne, here are the measurements you asked for and another photo:

11in from center of drain to stud wall
34in from center of drain to first joist hole
Joist hole: 7/8” from top of joist, 3.25” to the bottom of hole

It looks like wet venting option you mentioned would require me to drill more holes through the joists and then remove a portion of the bathroom subfloor and tie it into the 1.5in copper drain.

This bathroom was remodeled once before and the shower was done the same way. We used it for a few years and never noticed an issue. Obviously it is not ideal but I’m curious to know given this, what condition would cause a venting problem. The poorly placed holes that were already drilled leaving me with not a lot of room for the curbless drain is making this difficult. Thank you.


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wwhitney

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It looks like wet venting option you mentioned would require me to drill more holes through the joists and then remove a portion of the bathroom subfloor and tie it into the 1.5in copper drain.
No, I apparently didn't explain it well. I drew it up below, where I extended one of your pictures to show the lavatory connections (and apparently drew it a bit askew). Brown is stud, green is 1.5", blue is your lavatory stack. You just have to go through studs and the bottom plate, no new holes in joists (unless I'm misinterpreting your photos).

Given the dimensions you provided and the existing problematic holes in the joists, I think the wet venting solution would be better than trying to get a dry vent takeoff on the shower trap arm. Also you have a choice of joist bay in which to make the connection, as long as the combo where the lavatory drain joins the shower drain is within 96" of horizontal developed length, and 2" of fall, of the shower p-trap outlet.

Cheers, Wayne

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Vinmassaro

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Thanks Wayne, this is very helpful and I didn't understand it fully the first time. Do you think it's possible that there is already a vent further in, between one of the other studs? I'm wondering if I should cut out a piece of subfloor where the vent stack goes through the floor to see?
 

wwhitney

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No clue.

But if you are replacing subfloor anyway, replacing a slightly larger area isn't much more work, so the cost of the exploratory demo is primarily the demo itself.

Also, it's worth noting that all subfloor should have its face grain (strength axis) oriented perpendicular to the joists. That goes for your depressed subfloor between joists as well.

Cheers, Wayne
 

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@wwhitney
I appreciate your responses. I took some time off this project and went back to it today. I did a little exploration and drilled a small hole in the floor between the joists where the lavs are connected to the copper drain. I used an inspection camera to take a look at things. The shower drain goes across the joists into a long sweep wye and connects to the toilet run. There is a copper vent off the shower run that connects to the copper lav drain. I believe it looks like the below. Will this work or need to be modified? Thanks!

shower_drain-1.jpg
 
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wwhitney

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I didn't review the whole thread, so just in regards to the last drawing, if the following are all true, then the lavs wet vent both the shower and the WC:

- The copper stub of lav drain at the bottom plate hits a LT90 and then the lav drain follows the green path, hitting the shower drain with a horizontal combo
- The PVC wye where the lavs join has a 2" outlet, and the green lav drain is 2".
- The shower trap arm from trap to where the green meets the blue is pitched at least 1/4" per foot, but the total fall is no more than the pipe diameter (2" ?)

If the second point isn't true (you have 1-1/2"), you could open up the subfloor and change the pipe size to 2".

Cheers, Wayne
 

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I didn't review the whole thread, so just in regards to the last drawing, if the following are all true, then the lavs wet vent both the shower and the WC:

- The copper stub of lav drain at the bottom plate hits a LT90 and then the lav drain follows the green path, hitting the shower drain with a horizontal combo
- The PVC wye where the lavs join has a 2" outlet, and the green lav drain is 2".
- The shower trap arm from trap to where the green meets the blue is pitched at least 1/4" per foot, but the total fall is no more than the pipe diameter (2" ?)

If the second point isn't true (you have 1-1/2"), you could open up the subfloor and change the pipe size to 2".

Cheers, Wayne

@wwhitney I finally opened this area up this morning. The 2” copper line that was here is actually cut and capped which I couldn’t tell with my inspection camera. The PVC lav plumbing is all 1-1/2", connects to the 1-1/2" copper pipe with banded fitting, which goes into a copper tee from 1-1/2" to 2". Things are pitched 1/4" per foot with less than 2" fall.

Can I cut and reconnect the shower 2in pvc to the copper, with which PVC fitting and a banded pvc to copper coupling?

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wwhitney

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Looking just at your last post in isolation, yes you could tie back into that copper 2" drain, assuming it's in good condition, and the shower is already vented, or it's close enough (within the vertical fall limit) that the lavs would wet vent the shower.

However, that copper fitting under the wall doesn't look right from what I can see. You need to check if it's a combo or a san-tee on its back. The latter would need changing to a combo. For which the cleanest option, if you can get access, is to cut the copper just downstream of the fitting, and replace the upstream lav and shower drains with new plastic.

Also, since your understanding of what the hidden pipes do has changed a couple times, I suggest pulling up another bay of subfloor (patching a 32" wide strip isn't much harder than patching a 16" strip--remember the face grain direction always goes perpendicular to the joists) so that you can visualize the full WC drain. Then if you diagram exactly what all the bathroom plumbing is doing, and what you want to achieve, I could take another look at everything.

Cheers, Wayne
 

Vinmassaro

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Thanks @wwhitney

Took up another section and pics are below. Also tried to get some closeups going into the wall. I'm not sure what that copper fitting is, it just looks like a straight tee. What would be easiest to cut that out right after the fitting? It's hard to get in there because it's under the wall.

I'm just trying to make sure the shower is properly vented, and in general, make sure the plumbing on the whole is correct before I continue renovating this bathroom.

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wwhitney

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Looking at your photos, there's no view of the vertical copper pipes more than about 4' above the floor. What do they do higher up in the wall? Is there anything draining down into either of them, or is there just an attic above?

Also, I've lost track a bit of how far along you are in your modification. Is the shower p-trap connected all the way to the combo you just uncovered on the WC line? And with no vent takeoff or other drain joining in?

Cheers, Wayne
 

Vinmassaro

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@wwhitney

Sure, here's a few more. There is just an attic above and the shower p-trap goes across the joists and connects to the combo on the WC line from my previous post. Thanks.

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wwhitney

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OK, now I have enough of a picture to comment:

(1) The previous work connecting the plastic WC drain to the cast iron used the wrong fitting. The fitting shown is only for use underground; above ground you need a rubber coupling with a continuous metal shield. If that's connecting 4" cast iron to 3" plastic, you could use Fernco Proflex 3000-43 or Mission Rubber CP-43. That assumes the cast iron outer diameter is the current standard, vs something older and thicker; best to measure the OD.

(2) Just looking at the shower drain for the moment, the drain path is fine if the slope everywhere is at least 1/4" per foot.

(3) For venting the shower, right now you have nothing intentional. The IPC does allow two fixture drains to join together (the WC and shower in your case) and go to a common vent, if the resulting vent location would work for each fixture alone (if the other weren't there). WC fixture drain length before venting is not limited by the IPC.

On the shower, the fixture drain length before venting (trap arm length) is limited by a maximum fall of one pipe diameter of the trap (so 2" in your case). With the minimum 1/4" per foot pitch, that gives a maximum length of 8', if you get exactly the minimum pitch.

Thus given what you have now, say you set up a laser level line around the room. Then you can measure down to the top of that LT 90 right at the trap (the barrel, not the hub), and compare that to what you get measuring down to the end of the 3" plastic WC/shower drain (right before the rubber coupling, that's close enough to the vent stack). If the difference is no more than 1 7/16" (that's 2" minus half the difference in pipe OD between 2" and 3" plastic, which is (3-1/2" - 2 3/8")), then the stack will vent your shower as is. [And if the length of the pipe run between those points is over 8' along the pipe, there's no way that could be true.]

So if that doesn't work out for you, you need to vent your shower drain via one of the methods discussed earlier in the thread (which I haven't reviewed right now).

Switching the shower drain to connect to the lav drain rather than the WC drain will only help you, best case, by about 16" of run (since the lav vent is one joist bay over from the 3" vent stack, so it's closer). And that would require that you change that copper fitting under the wall, plus possibly lift it and the downstream drain up a little (to hit your 2" maximum fall). In other words it only makes sense if the current arrangement has just a little too much fall (like 2-1/4" instead of 2") and that reduction in 16" of run would make the difference.

Cheers, Wayne
 

Vinmassaro

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@wwhitney appreciate the info as always. I measured today and the difference in height from the trap to the rubber coupling using my laser level is approximately 3-5/8". The linear pipe distance is approx 149”. Where does that leave me, am I close enough? If not, is upsizing the toilet pipe to 4in PVC help me? Thanks.
 
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