Shower Drain Offset

[NorthTexas]

Is my configuration for offsetting my new shower drain ok and Code compliant ?

As you can see, the offset is ~ 4".

This is in a post-tension concrete slab. I can't put the p-trap directly under the drain because there is a beam right there. I have chopped out as much concrete as I can right there.

It's a new Kerdi drain with the riser connected to a 45, connected to a short piece of straight pipe, connected to a street 45, connected into the inlet of the p-trap.

I want to make sure this is ok before I glue it all up - thank you very much for your help !

 

[wwhitney]

Along as the street 45 is going into a proper 2" p-trap, your arrangement is acceptable.

Cheers, Wayne

 

[Sponsor]

 

[NorthTexas]

Thank you Wayne.

I assume it is a proper p-trap, it's one I simply bought at HD. My drawing maybe didn't look perfect of it ?

Here is actual setup as I have it sitting in the slab hole.

Good to go ?

 

[wwhitney]

Once you glue it up, sure. : - )

Cheers, Wayne

 

[NorthTexas]

How do you get the p-trap level given the drain line pipe has a 2% slope on it at the end there ?

Do you level the trap:

1. By not quite setting the hub of the weir all the way onto the drain line pipe = bottom of it all the way on but the top not quite on all the way, so the bottom of the weir (the bottom of the street end) is level and thus the p-trap can be set level ?

2. Not quite setting the hub of the p-trap all the way onto the street side of the weir like above to get the trap level ?

My thinking is if the p-trap is level, then the top of my plumbing run is level for my shower drain tail and thus the drain is level.

Thanks so much.

 

[wwhitney]

How do you get the p-trap level given the drain line pipe has a 2% slope on it at the end there ?

There's enough adjustability/slop in the connections that you should be able to get it very close.

Your free end of pipe sticking out of the soil is fixed unless you want to remove alot of soil and likely concrete. So I'd suggest sticking a torpedo level on the inside bottom of the pipe to confirm it is at least pitched away from the hole, and if it is, accept it as fixed. Then I'd suggest just working on the two pieces of the p-trap to start, and find a configuration where the inlet hub on the u-bend is very close to level both ways. That's good enough, mark the positions, glue it up, and double check level while you can still make minor corrections.

Then as you add your 45s and intermediate piece of pipe, similarly check top of the top 45 hub for level. That's more important than the inlet of the u-bend, but you have even more points of adjustment to get there.

Cheers, Wayne

 

[NorthTexas]

So I'd suggest sticking a torpedo level on the inside bottom of the pipe to confirm it is at least pitched away from the hole, and if it is, accept it as fixed.

Thanks Wayne - yes I did just as you said and it is pitched away from the hole.

I'd suggest just working on the two pieces of the p-trap to start, and find a configuration where the inlet hub on the u-bend is very close to level both ways.

Agree - but do I manipulate the hub of the weir and have the street end of the weir straight into the outlet side of the trap u-bend; or manipulate the hub of the outlet of the trap u-bend (meaning the hub end of the weir is fully seated onto the drain like pipe end) ?

 

[wwhitney]

but do I manipulate the hub of the weir and have the street end of the weir straight into the outlet side of the trap u-bend; or manipulate the hub of the outlet of the trap u-bend (meaning the hub end of the weir is fully seated onto the drain like pipe end) ?

The weir is a point on the inside of the trap elbow, where if you slowly filled up the trap from the inlet side, water would first crest over and start spilling down the horizontal drain pipe going into the soil. So I think you mean trap elbow instead of weir.

All joints should be fully seated (well, if you end up with an internal gap of 1/8" or less, not worth redoing the joint)--you can't actually do that via a dry fit, as the plastic is an interference fit and depends on the solvent cement to soften both materials to fully seat the pipe/spigot end into the hub. While soft you can tweak that joint a tiny amount.

So if the trap outlet elbow is exactly 90 degrees (I've never checked it, could it be 91 degrees to help with the slope?), and if the u-bend has its two hub ends in exactly parallel planes, and if the joints were all perfectly coaxial, you are right that any slope on the trap arm would show up as an out-of-level condition on the u-bend inlet hub. But those are not all exactly true, and so you can get the u-bend inlet hub more level than that idealization would suggest. Even if the u-bend inlet hub is sloped 1% some way, you can fix that with your double 45 offset and the final result will work fine.

So dry fit the two pieces of the trap the best you can (deep enough so that everything is close to coaxial, but not so deep that you can't pull it apart again) and mark the orientations. Note how it is out of level on the u-bend inlet hub (if it all) and push/pull on the assembly in the proper place location to improve that. Glue it up, put your level on the u-bend inlet hub again, and if it is out of level the same way, push/pull on the assembly a bit as the glue hardens to improve the final result.

For the case of a planar p-trap, what you'd expect from the idealized model is that the far edge of the u-bend inlet hub would be a bit higher than the the downstream edge, and so pushing down on that far edge a bit would help reduce that discrepancy. While if you found any out-level-ness side to side, you'd rotate the trap elbow on the trap arm pipe to fix that. The geometry will be a bit different as your trap is not planar, but I'd guess something similar to be true--if in your picture the pipe is exiting the hole at 1 o'clock, you may need to push down a little on the trap inlet hub at around the 7 o'clock position. And/or push down a little on the trap elbow.

Cheers, Wayne

 

[NorthTexas]

Thanks so much Wayne.

This is what I was trying to ask.

 

[wwhitney]

Both, as required.

If the elbow is a true 90, and if the two hubs on the u-bend are in parallel (perhaps identical) planes, then the only way to can get to level on the right is by slightly cocking some of the joints. Easier to get a little bit of deviation out of two joints than get all the deviation out of one joint.

Basically, your concern is valid on a theoretical level but tends not to be an issue on a practical level.

Cheers, Wayne

 

[NorthTexas]

Haha, that's funny - "valid on a theoretical level but tends not to be an issue on a practical level" - story of my life as a PhD !

 

[NorthTexas]

Made up a little template and dry fit all the pieces - look ok ?

 

[wwhitney]

Made up a little template and dry fit all the pieces - look ok ?

What your pictures show looks fine.

Note that when you glue up your joints, they are all going to slide in farther than your dry fit. So starting at the existing pipe, your outlet elbow is going to slide farther on. That's going to move everything towards the pipe a little. Then the u-bend will slide up farther than it is; that shouldn't change the location of anything upstream of it. If you want the last pipe to appear in the middle of your cardboard template, you'll want to redo your dry fit at this point; I bet the distance between the two 45 fittings is going to grow.

If you have a critical length, then a good way to get close is to take the dry fit, measure the exposed pipe between the hubs, add to that length the depth of each socket (should be 3/4" for a 2" joint), and then subtract maybe 1/8" to allow for variation in how deeply the pipe seats, based on your end prep, how hard you push it together, etc. Even better is to do a test glue up with some extra pieces of the same size--just measure the length of a scrap of pipe, glue on two fittings with hubs of the same depth as you are using, and measure the exposed length of pipe in the final result.

Cheers, Wayne

 

[Reach4]

Your template may be doing what is described in

but if it is not, you might gain from watching that video.

 

[NorthTexas]

Ok, glued the p-trap elbow in place and will let that set up overnight and then add the p-trap tomorrow. I put my little 3" level on the bottom of the street side and it is level across the left to right sides, so it's not cockeyed.

 

[NorthTexas]

Can't see anything Reach4 - is there supposed to be a video or link there ? Thanks.

 

[Reach4]

Can't see anything Reach4 - is there supposed to be a video or link there ? Thanks.

Yes. I think you have something turned off. Try taking the ZZZ off of ZZZhttps://youtu.be/-PDNxJG4Rtk

 

[NorthTexas]

Thanks Reach4.

LOL - that's the video where I got the idea for the template last night. My slab is already busted out so I put down the piece of cardboard this morning and then put my shower tray over it, marked the drain hole, cut it out and taped it down on the floor in place.

 

[NorthTexas]

Just put the p-trap in - it's pretty much level each way and centered right on my template lines. I'll let it set up for a couple of hours and get back at this afternoon. Thank you all for your help so far, I really appreciate it !

 

[NorthTexas]

How thick should the covering layer of actual concrete (is that called a "cap" ?) be after refilling the plumbing hole with all the dirt I took out of the hole in the slab ?

Do I just add back the dirt in layers, and if so, how thick should each layer be, and compact each layer up to level from answer to question above ?

Thank you.