2" trap for a shower in a 2x8 floor joist

[jwarr]

Hey all, I've seen a few discussions on fitting a 2" trap for a shower in the vertical space for a 2x8 floor joists. I've seen a few solutions and wanted to see if anyone sees an issue with this. Take a look at the pics but essentially it is 3 90s and 2 45s so that there is enough clearance to lay subfloor without the drain pipe being peeking above the floor joist. Conceptually I think it works since the highest point of the "trap" is lower then where it starts to slope down to drain, therefore keeping water in the trap. Only thing it is draining is a shower. Thanks in advance!

 

[wwhitney]

So Charlotte's catalog says the center line to center line height of the outlet of a 2" trap (relative to the lowest part of the U-bend) is 4-3/4". Add 2-3/8" for the OD of a 2" pipe, and then 3/16" because the outlet is a hub (hubs have 2-3/4" OD, so the radius is 3/16" more). That makes 7-5/16", which I guess just fails to fit in a 7-1/4" joist bay.

That perhaps explains why the catalog also shows a low-profile 2" trap, where the outlet is 3/16" lower. That makes the total height 7-1/8", which should fit in a 2x8 joist bay. Charlotte part 710, could be hard to source.

Here's a place carrying Lasco D706-021, and the Lasco DWV catalog says it has a center-to-center height of 4-1/2":

You are being redirected...

Dimensional Catalogs | LASCO Fittings

www.lascofittings.com

Of course, for this to work, you need to be able to make the vent connection (wet or dry) in the same joist bay as the shower trap. Because the trap arm can fall at most 2", your trap outlet will be almost at the top of the joist bay, and any holes in the joist have to be at least 2" from the top or bottom.

Cheers, Wayne

 

[Sponsor]

 

[jwarr]

So Charlotte's catalog says the center line to center line height of the outlet of a 2" trap (relative to the lowest part of the U-bend) is 4-3/4". Add 2-3/8" for the OD of a 2" pipe, and then 3/16" because the outlet is a hub (hubs have 2-3/4" OD, so the radius is 3/16" more). That makes 7-5/16", which I guess just fails to fit in a 7-1/4" joist bay.

That perhaps explains why the catalog also shows a low-profile 2" trap, where the outlet is 3/16" lower. That makes the total height 7-1/8", which should fit in a 2x8 joist bay. Charlotte part 710, could be hard to source.

Here's a place carrying Lasco D706-021, and the Lasco DWV catalog says it has a center-to-center height of 4-1/2":

You are being redirected...

Dimensional Catalogs | LASCO Fittings

www.lascofittings.com

Of course, for this to work, you need to be able to make the vent connection (wet or dry) in the same joist bay as the shower trap. Because the trap arm can fall at most 2", your trap outlet will be almost at the top of the joist bay, and any holes in the joist have to be at least 2" from the top or bottom.

Cheers, Wayne

Hey Wayne, thanks for the response!

Yes, what you have is what I have used in the past. Unfortunately I've been trying to find it and it has been out of stock locally.

As far as the vent connection, it'll be located in the wall shared with the shower, so no issue there. This drain is running parallel to the joists until it heads south to the basement so I don't have to bore through any joists.

Barring being able to find the low profile trap you cited, any reasons not to leave it like it's built? Functional I think it is the same, just laying at about a 40 degree angle.

 

[wwhitney]

I'm not going to say that your collection of fittings definitely isn't code compliant, but I am going to say that there is at least some doubt. So given that a proper p-trap is available for your situation, I wouldn't ever use anything else.

I suggest looking harder for the low profile 2" p-trap. Or if the interference is just 1/16" at the outlet hub or a normal p trap, relieve the backside of the subfloor just at the outlet hub.

Cheers, Wayne

 

[jwarr]

I'm not going to say that your collection of fittings definitely isn't code compliant, but I am going to say that there is at least some doubt. So given that a proper p-trap is available for your situation, I wouldn't ever use anything else.

I suggest looking harder for the low profile 2" p-trap. Or if the interference is just 1/16" at the outlet hub or a normal p trap, relieve the backside of the subfloor just at the outlet hub.

Cheers, Wayne

Sounds good, I appreciate the feedback! I agree with you, I'll expand my search radius and see what I can find. I'd rather be on the safe side. Thanks Wayne!!

 

[PitaJim]

i am have the same problem .what did you end up doing ?