Shower P Trap

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originaltwotone

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Here is from the backside of picture #2 with a 2'' and 1.5'' P-Trap resting on the drywall. So it seems I'm going to have to rip out the sink drain and raise it in order to get the 3'' line high enough for the shower PTrap to work. I think I might have to go 1.5 ptrap because when I raise the 3'' pipe I have to leave enough room for the sink drain to have proper slope.
But even if I get this done, based on my limited research and knowledge and as mentioned, I'm worried about proper venting.

I can't believe this passed inspection when the house was built.
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wwhitney

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FWIW, if the 3x3x2 san-tee (that needs replacing) where the lav and the tub join is carrying only 1 or 2 lavs and one tub, there's no need to upsize to 3" at that point. You could replace it with a 2" combo, and run 2" to the shower drain. The combined lav/tub/shower drain does need to be 3".

Also, what is the elevation above the drywall of the center line of where the sink drain comes into the joist bay. And how far parallel to the joists from there to the shower drain location?

Cheers, Wayne
 

John Gayewski

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I think i would bend the rules and turn the trap at a 45.

Or change it all to 2"and raise it.
 

originaltwotone

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First off I wanted to that you all for the help. Its hard to trust a 'pro' when you read so many horro stories of supposedly professionals doing it wrong.

It's 4'' to the centerline of the sink drainline from the drywall. When you look at the second picture, my concern is that at that height it's for a 1.5 in trap.

Wayne if I'm understanding you correctly this is your recommendation:
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Jeff H Young

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Here is from the backside of picture #2 with a 2'' and 1.5'' P-Trap resting on the drywall. So it seems I'm going to have to rip out the sink drain and raise it in order to get the 3'' line high enough for the shower PTrap to work. I think I might have to go 1.5 ptrap because when I raise the 3'' pipe I have to leave enough room for the sink drain to have proper slope.
But even if I get this done, based on my limited research and knowledge and as mentioned, I'm worried about proper venting.

I can't believe this passed inspection when the house was built.
View attachment 90985
View attachment 90986
it was built this way in a place with codes and inspections ? Id be concerned about what we dont see as well
 

wwhitney

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It's 4'' to the centerline of the sink drainline from the drywall.
That's going to be a problem, as the elevation difference between the centerline of a 2" trap outlet and the bottom of the u-bend is almost 6". That means that the trap weir is at least 5" above the drywall ceiling. While your 2" sink drain (it needs to be 2") is at 5" on the top inside. Which almost works if there were no fall in between the two locations, but the drain has to fall at 1/4" per foot. How far is it along the joist bay between where the sink drain comes in and where the shower drain come down?

I had suggested that the 3" line doesn't need to start until the fitting where the shower joins the lav/tub, but actually, starting it where the lav joins the tub as you currently have (with the wrong fitting) effectively gives you an extra 1/2". Also, you could cut a whole in the drywall and cover it with an access panel, that would give you another 1/2". Lastly there's a low profile solvent weld 2" p-trap that saves you 1/4".

You could also raise where the sink drain comes into the joist bay (and everywhere upstream). If the center line is at 4", the joist looks like a 2x10 or 2x12, so your maximum hole size is 3" or 3.75". So if you have a 2-1/2" hole now, you should be able to enlarge it at least 1/2" and gain a 1/2" that way.

Worst case, the IPC does allow a shower on a 1-1/2" drain line, and so if you switch to a 1-1/2" trap, that would save you 1".

Cheers, Wayne
 

wwhitney

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I don't follow the comment "raised up for p-trap 45 down to clear toilet supply". If you're talking about a drop between the shower trap and the wye where the sinks/tub join, that's not allowed and is part of the problem with the current config. Also, upsizing the shower trap arm to 3" doesn't help you in you any way. And the tub would now need a 2" trap with careful attention to slope for the 7' long tub trap arm.

If you are willing to redo the sink drains, why not split them? The left side (in the drawing) sink can stay as is. The right side sink can take the direct cross joist route towards the shower location, so that it can arrive with greater elevation to permit wet venting the shower.

Cheers, Wayne
 

originaltwotone

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Wayne- thanks for your patience. I'm shocked any of this passed inspection. I doubt my sink drains are at a proper slope as it is.
I have 9'' joist. As far as I've been able to research, you shouldn't drill holes within the top/bottom 2'' of joists. That means the pipe center line starts at 6'' with 2 1/4'' drop (9') that puts it even lower than it is now 3 3/4''. That was the reason I thought to move it to where the 3'' line is lower.
I have to raise the 3'' line for the shower, but it has to drop for the supply and toilet. If I redid the entire 3'' pipe at the height required for the shower trap, the 3' 90 for the toilet would stick up thru the floor.


img20230220_17550813.jpg
 

wwhitney

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As to the question in the last picture, no that drop is fine. Your earlier picture made it look like the drop was going to occur between the shower trap and the wye to shower, which isn't OK.

Cheers, Wayne
 

originaltwotone

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As to the question in the last picture, no that drop is fine. Your earlier picture made it look like the drop was going to occur between the shower trap and the wye to shower, which isn't OK.

Cheers, Wayne
So with that do you agree that my only choice is to move the sink drain to the right and send the tub there as well as long as I can get the slope correct?
 

wwhitney

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I agree that if a 2" drain goes through 8' worth of joists (I'm assuming you might get 6" at either end within the joist bay), then the center line has to drop 2" while doing that. And then if it goes another 8' (turning the corner plus the 7') it has to drop another 2". Since the highest the center line could be when the sink drain goes through the first joist is 5-3/4" above the the bottom of the joist (9" less half a 2-1/2" hole less 2" of wood above the hole), the center line would be at only 1-3/4" to 2" above the bottom of the joist at the time you hit the shower drain. Which doesn't work.

BTW, that's another reason they may have upsized to 3" earlier than expected, as a 3" line is allowed under the IPC to only slope at 1/8" per foot. Which would save you one inch of fall within the upper (on the page) joist bay.

I agree the right (on the page) sink drain would need to go straight towards the shower to have any hope of wet venting the shower. I think the left sink drain could stay on its current routing and hit the tub, rather than extending the tub trap arm.

Even so, you're going to be fighting for elevation if the joists are 9" tall. If the right sink drain stays 2", then after the 8' of joists you end up with its center line 3-3/4" above the bottom of the joist. While your 2" shower trap outlet is at 6" above the bottom of the joist, more than the maximum 2" difference allowed. [And changing the sink drain to 1-1/2", which the IPC allows for a single sink wet vent, doesn't help you, as what really matters is the top of the pipe, which is constrained the same way by the maximum height of the first hole in the first joist it goes through.]

So you might still have to drop the trap into the drywall. Or use a 1-1/2" shower trap (saves you about 1" IIRC). Or figure out how to dry vent the shower.

Cheers, Wayne
 

originaltwotone

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First I want to thank everyone again for their help. Some things came up and the project had to be put on hold, but I had decided to dry vent the shower through the shower wall into the attic and connect to the main stack vent which I assumed was up in the attic.
Well of course, nothing in this project has gone to plan.

Here is a picture of how the venting is in the bathroom. The question is, would the proposed red vent line be ok.

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wwhitney

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I have not reviewed the rest of the thread, but a dry vent has to come off the trap arm vertically and stay vertical until at least 6" above the fixture flood rim. So the red line can't be a dry vent, as it is horizontal below the floor.

Cheers, Wayne
 

originaltwotone

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I have not reviewed the rest of the thread, but a dry vent has to come off the trap arm vertically and stay vertical until at least 6" above the fixture flood rim. So the red line can't be a dry vent, as it is horizontal below the floor.

Cheers, Wayne
Wayne- I figured as much.
Does the Main stack vent function as the shower vent trhough the 3'' drain? It's 48'' from the p-trap
 

wwhitney

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Given that the DWV is not what you were expecting, I will continue to not review the earlier part of this thread. But I think it's worth looking at the big picture at this point. So:

Can you either draw a floor plan showing the fixtures layouts and all the horizontal DWV (with the vertical sections shown as circles), or else mark up the picture in the last drawing with all the existing DWV and the proposed locations of all the fixtures in the final configuration?

As to the last question, the 3" drain in question is the WC fixture drain? With no vents before the stack? Is anything draining down that stack from above?

Cheers, Wayne
 

originaltwotone

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Wanye, thanks for your patience.
I'm not trying to move any fixtures, I just had a gut feeling when I took apart to find the leak, it wasn't done right to begin with.
I had a few estimates done, all in the 3k+ range and not one mentions correcting the venting.
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wwhitney

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Given that nothing is moving, I need to go back and review the whole thread, but my initial reaction to your drawing is

(a) there's no venting problem, the 3" horizontal drain is a wet vent for your shower, so you can just connect to it with a 3x3x2 wye (or 3x2x3 wye) and your shower is vented (maximum 2" fall from trap outlet to wye)
(b) the only dry vent you need is the one at the sink that goes through the roof; that horizontal red dry vent from the top of the stack is not required, as everything entering the stack is already (wet) vented.
(c) I should have asked for the floor plan at the beginning of the thread. : - )

Will respond more definitely later.

Cheers, Wayne
 

wwhitney

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OK, I had a chance to review the whole thread. Some of my comments from yesterday were not quite on the mark.

In the first round of discussions, the issues were that (a) wet venting the shower is fine looking at the plan view, but is hard or impossible giving the vertical space available. In that you have 9" joists, and the horizontal drain is traveling 16' through the joists before reaching the shower, so the horizontal drain is going to be too low for the shower trap to comply with the trap weir rule while not sticking through the drywall below. And (b) the tub/sink drain connection was using a san-tee on its side rather than a combo.

Part (b) is fairly straightforward, you just need to redo that connection. This assumes that the tub trap arm from the trap to that san-tee on its side doesn't fall more than one pipe diameter, or 1-1/2" if you have a 1-1/2" trap. And the tub trap should all be solvent weld, no unions or slip joints, unless you have an access panel to get to those unions or slip joints.

As to (a) you said you were going to dry vent the shower, but in yesterday's post the issue is how to run that dry vent. The red line doesn't work. Is the yellow line actually present, or something you propose to add? It's not required to be added, and it doesn't directly help you vent the shower. That is, since the shower would be joining the 2 sinks and the tub coming from upstream, and also hit the WC downstream, all before hitting the stack, putting a vent on the stack doesn't work for venting the shower. Too many fixtures involved (common venting is limited to 2 fixtures).

Now if you can run the shower drain separate from the sink/tub/WC, at a higher elevation, and you hit the stack with a separate san-tee above where the sink/tub/WC hits the stack, and the stack has a vent off the top that follows the yellow line, that works to dry vent the shower. I'm a little unclear if the elevations would allow that to work. A variation on this is to have the shower and the WC join and go to the vented stack as the highest fixtures connected, and then bring the tub/sinks into the stack lower.

Another option would be run the shower drain separately to the wall with the stack, but if you don't have room to stack san-tees on the stack, the shower trap arm could hit its own san-tee to the side, with the dry vent rising up to join the yellow line, and the drain dropping down to join the stack lower in the wall below via a wye.

You could also run a dry vent up the shower valve wall and then across what is currently an opening that goes to the ceiling by enclosing the top of that opening. Assuming I am interpreting correctly that the left side wall of the corner with the tall blue level leaning in it is in plane with the shower valve wall, which maybe it is not.

Lastly, you'd have to carefully check the elevations, but it might be possible to wet vent the shower by splitting the sink drains as in the drawing below. [I.e. the separate left hand sink drain would follow a route close to the red vent line in your picture from yesterday.] Green = 1.5", Blue = 2", Red = 3" and I am just showing minimum sizes. Each sink is dry vented by a 1.5" vent denoted by the circle; those vents can combine at a height at least 6" above the sinks. Then each sink drain can run through the floor framing as a 1.5" wet vent (although on the left you could reuse the 2" run you have). The right hand sink drain might end up high enough in the joist bay to allow wet venting the shower trap. It would be close--if the floor is level, and the hole through the first joist is 2" (clear) down from the top of the joists, the sink center line is about 6" above the ceiling at that point. After 8' of run, that's 4" above the ceiling. If you use a low profile shower trap, it might work out, or you might be shy 1/2" of elevation.

Cheers, Wayne


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originaltwotone

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Thanks for taking so much time to help me out.
Yes the yellow vent is already there.
The shower wall and linen closet are not in plane- so that's out.

I think my best option is the separate sink drains you proposed. I kept my drawing simple, but the the vent coming of the stack is already a bunch of elbows(see pic below), no way I'm adding anything there. What you don't see in the picture is the toilet supply line just behind the camera that is 1/2 between the floor and top of the 3'' drain- so that would require reroutiing to allow the shower to head over to the stack, even then, don't see how I'd connect it to the stack with what's there.

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