Shower p-trap vent location and slope

[Sailor]

I'm remodeling my master bathroom and going with a Kerdi channel drain and larger shower extending to where we used to have a sink. I tied the new drain where the sink drain used to be.

I'm wondering whether the vent should have been connected closer to the p-trap.
This is the first time I do this, does it look right to you?

Things to note:

1. I used 2x 22.5 degree elbows to slope the first feet, then sloped the rest slightly to the sanitary tee and vent elbow (can see better on the second picture, capped to stop odors overnight).
2. Permanently capped the old vent pipe from previous shower location on the right side.

Thanks in advance for any advice!

 

[Sailor]

NO pictures here

Sylvan, thanks for letting me know, it's odd because I can see the pics in my post.
I've attached the same pics to this message, hope it works now.

 

[Sponsor]

 

[Sylvan]

Yikes .. way to many fittings

Looks like you could have used 2- 45 deg fittings (1.4142) 45 deg offset

Heck of a line to snake

 

[Reach4]

Looks like the shower trap arm does not stay horizontal until vented.

 

[Sailor]

Looks like the shower trap arm does not stay horizontal until vented.

You're correct, I thought the line should be sloped 2% until the sanitary Tee.
Should it be horizontal from the p-trap to the where it vents?

 

[Reach4]

You're correct, I thought the line should be sloped 2% until the sanitary Tee.
Should it be horizontal from the p-trap to the where it vents?

2% is considered horizontal for this purpose. In drain and vent lines, there is no horizontal pipe in the mathematical sense.

Cross brace would have to be moved so that trap can drop and that 22.5 shortly after the trap could be removed.

 

[Sailor]

Yikes .. way to many fittings

Looks like you could have used 2- 45 deg fittings (1.4142) 45 deg offset

Heck of a line to snake

Sylvan, thanks for the feedback. I can go back and fix it, but can't change to location of the Sanitary Tee and vent. And the P-trap also need to be exactly where it is to receive the long 72" channel drain.

When you say 2- 45 deg fittings, you mean horizontally, cutting through the joist at 45 deg?
OR 2- 45 deg fittings vertically instead of the 2- 22.5 that I used? In this case what difference would it make?

 

[wwhitney]

Here's what you need to do:

In plan (ignoring altitude), you want p-trap --> outlet at 45 degrees to the joist --> drill the joist at a 45 degree angle -> "horizontal" pipe through to a single 45 degree fitting lined up with the sanitary tee --> "horizontal" pipe to the sanitary tee.

Vertically, you want to do all of the above at a 2% slope. So say the pipe from the joist to the sanitary tee is 4' long measured at the pipe center line. Then you want the pipe going through the joist to be 1" higher than the inlet of the sanitary tee. That determines your p-trap height, looks like you'll be lowering it by removing the block below it.

Note that your hole through the joist needs to be 2" clear from the top and bottom, but it looks like that restriction won't conflict with the above.

Cheers, Wayne

 

[James Henry]

It will not drain properly the way you have it. Would not pass inspection. Take Wayne's advice.

 

[Sailor]

Here's what you need to do:

In plan (ignoring altitude), you want p-trap --> outlet at 45 degrees to the joist --> drill the joist at a 45 degree angle -> "horizontal" pipe through to a single 45 degree fitting lined up with the sanitary tee --> "horizontal" pipe to the sanitary tee.

Vertically, you want to do all of the above at a 2% slope. So say the pipe from the joist to the sanitary tee is 4' long measured at the pipe center line. Then you want the pipe going through the joist to be 1" higher than the inlet of the sanitary tee. That determines your p-trap height, looks like you'll be lowering it by removing the block below it.

Note that your hole through the joist needs to be 2" clear from the top and bottom, but it looks like that restriction won't conflict with the above.

Cheers, Wayne

Wayne,
Makes perfect sense, many thanks for the detailed description.
Will redo as you described.
Cheers!

 

[Sailor]

Here's what you need to do:

In plan (ignoring altitude), you want p-trap --> outlet at 45 degrees to the joist --> drill the joist at a 45 degree angle -> "horizontal" pipe through to a single 45 degree fitting lined up with the sanitary tee --> "horizontal" pipe to the sanitary tee.

Vertically, you want to do all of the above at a 2% slope. So say the pipe from the joist to the sanitary tee is 4' long measured at the pipe center line. Then you want the pipe going through the joist to be 1" higher than the inlet of the sanitary tee. That determines your p-trap height, looks like you'll be lowering it by removing the block below it.

Note that your hole through the joist needs to be 2" clear from the top and bottom, but it looks like that restriction won't conflict with the above.

Cheers, Wayne

I took everything apart today and managed to save the sanitary tee after a couple hours grinding down and removing the street elbow I had in there, see pic.

But it seems I have another problem; sanitary tee seems to be too low?
The verticle difference from sanitary tee to the trap weir is 2-1/2" with the trap resting on the sheetrock, and the total pipe length to sanitary tee is only 32" long, so to comply with the 2% drop that should be just short of an inch.

Could I use 2x 45 degree elbows at the sanitary tee just to raise its outlet height? Or to the trap outlet to bring it down? I'm afraid to use a bunch of fittings all over again!

 

[wwhitney]

So, you are off 1/2". The 2% slope is the minimum, the other rule for the trap arm is the one about the trap weir, so it would be fine to fall 2" (no more) over that 32". [The trap weir rule says, in effect, that in your last picture, a level rod raised up as high possible in the san-tee opening should fit into the trap opening.]

The proper solution is to raise the sanitary tee. Also, it would be better to jog the vent into the wall with two 45s, or at least a (street) medium 90 followed by a long turn 90 (traveling upstream), although I'm not clear on whether the IPC actually requires that (the UPC would).

How level are your floor joists? Any chance 32" away they've sagged 1/2"? Or have sagged 1/4" and you could invade the drywall 1/4"?

You might be able to find a low profile trap that is a 1/4" or 1/2" shorter, that would help.

If your shower has heads flowing less than 5.7 GPM in total, the IPC would allow a 1-1/2" trap, which should fit, but that seems less desirable than a 2" trap.

Those are the only options I can think of.

Cheers, Wayne

 

[James Henry]

You cannot put a vertical jog in any drain before the vent except floor drains. it is called " breaking the vent". Cut the drain stack below and couple in a new line then put the santee where it works. It's the same reason why you can't use a combo in the vertical position.

 

[Sailor]

So, you are off 1/2". The 2% slope is the minimum, the other rule for the trap arm is the one about the trap weir, so it would be fine to fall 2" (no more) over that 32". [The trap weir rule says, in effect, that in your last picture, a level rod raised up as high possible in the san-tee opening should fit into the trap opening.]

The proper solution is to raise the sanitary tee. Also, it would be better to jog the vent into the wall with two 45s, or at least a (street) medium 90 followed by a long turn 90 (traveling upstream), although I'm not clear on whether the IPC actually requires that (the UPC would).

How level are your floor joists? Any chance 32" away they've sagged 1/2"? Or have sagged 1/4" and you could invade the drywall 1/4"?

You might be able to find a low profile trap that is a 1/4" or 1/2" shorter, that would help.

If your shower has heads flowing less than 5.7 GPM in total, the IPC would allow a 1-1/2" trap, which should fit, but that seems less desirable than a 2" trap.

Those are the only options I can think of.

Cheers, Wayne

Good points Wayne, thanks.
I measured the elevation gap 32" away from san-tee to find only 1/8" sag, so no luck there.
I'll install two independent showers using the previous sink water lines and previous shower lines, so I expect high flow when wife and I are in the shower
I'll do the proper solution (raise the san-tee) later today and send you pictures before I glue everything together.
Cheers!
Vinny

 

[Sailor]

You cannot put a vertical jog in any drain before the vent except floor drains. it is called " breaking the vent". Cut the drain stack below and couple in a new line then put the santee where it works. It's the same reason why you can't use a combo in the vertical position.

Thanks James, I'll do exactly that later today and post pictures.

 

[Sailor]

Hey Wayne, James, all,
Just wanted to show you what I've done and thank you for your help!
All dry fitted now with 2% slope and single 45 degree between santee and trap outlet at 45 degrees.
I managed to remove the glued santee and place a coupling beneath a new santee to raise it about 1-1/2".
As for the vent, the best I could fit below the recessed subfloor was two medium 90s (one street and one normal). I had to cut part of the subfloor support which I will cover with metal plate. Shower tray at that location is another 2" thick plus tile.
I'll glue everything tomorrow so if you can think of anything pls let me know.
Thanks again for all the assistance!

 

[wwhitney]

Looks good, I don't see anything amiss with the plumbing.

For a shower tray, it's important that the substrate be dead level in both dimensions. Is that what you have with your combination of joist tops and inter joist subfloor pieces?

Likewise, if you use the metal strap, you'll want to recess it slightly in the wood supports so it doesn't make a bulge in the subfloor there.

Cheers, Wayne

 

[Sailor]

Looks good, I don't see anything amiss with the plumbing.

For a shower tray, it's important that the substrate be dead level in both dimensions. Is that what you have with your combination of joist tops and inter joist subfloor pieces?

Likewise, if you use the metal strap, you'll want to recess it slightly in the wood supports so it doesn't make a bulge in the subfloor there.

Cheers, Wayne

Yes it is dead level in both directions, but only after I planed some joists with electric planer in some places almost 1/4" and chiseled the ends, others didn't need any work, really a critical step!
Cheers.