Aligning shower drain around joist

[MikeCO]

I need to move this shower drain over to the red circle to align with a prefab shower base. The exact center of where the drain needs to go is 1" off of the joist. At the wye in the bottom of the picture, there is ~3/4" between the top of the pipe and the bottom of the joist.

My plan was to cut the line between the wye and the p-trap and put in a copper/PVC coupling. Then, extend the line under the other joist (I think I should be okay with getting enough rise under the joist if I have 3/4" to work with) and put the p-trap on the same side of the joist as the drain.

One other problem I think I'll have is that if I use 2" pipe here (the existing copper pipe is a bit over 2" OD), since I only have 1" of space next to the joist, it's not going to be exactly aligned where it needs to be since the OD of the PVC will be 2.3" or so.

Given this, it seems like I could either:

• Switch from the copper to 1.5" PVC which would have a smaller OD and could come up exactly in the right spot
  
  
• Use 2" PVC and an offset drain
  

Any thoughts on the best way to do this?

 

[Jadnashua]

If this is being inspected, you cannot use a 1.5" drain on it when you already have 2" lines unless your inspector is really accommodating. You could box out that area and then be able to put the drain where you wanted.

One of the pros may have some other ideas. That's one of the hassles with prefabbed pans...there's not much leeway about where the drain must be unless you can move the walls to the whole thing. Had you considered doing a tiled shower? Then, you can move the drain where you need it within reason.

 

[Sponsor]

 

[Jeff H Young]

Well you cant really head the joist out with sheet metal there. Id have to see the shower pan the od of the drain is going to get in the way of joist . Never heard of a custom fiberglas pan but you might check. Everything I do Is hot mop or 90 percent hot mop. Trust me Ican make the plumbing work but the structure will be compromised

 

[MikeCO]

Thanks for the input. Does anyone have any thoughts on using an offset drain? Here are links to the shower & shower pan spec (pan measurements on page 5 of the 2nd PDF - Model VG06039):
https://www.wayfair.com/home-improv...-included-vgu3162.html?piid=28304965,28304967
https://secure.img1-fg.wfcdn.com/docresources/0/140/1400497.pdf

 

[Jeff H Young]

the 6039 puts the drain right on the joist? If it clears joist then use it. Mostly if customer wants an offset drain (never heard it called that) then thats what we use . Sometimes having the drain other than dead center makes it better as your not stepping on it. If you find something you like get it . The joist is a problem other than just a little cutting you dont want to hack into it.

 

[Terry]

I would move the drain location by either getting a custom pan or a pan in place.

 

[Jadnashua]

If you wanted to go with a tiled shower base, at least a few companies will make the base for you that is custom for your space. I think one is Laticrete. It's made of high density foam that you then cover with a waterproof, tileable membrane. To use their system, you should use that on the walls as well. It costs the same as their 'standard' sizes and takes only a little time (well, who knows today!?).

 

[Jeff H Young]

Several options no need repeating let us know which way you go and good luck on project hope options are satisfying and not something you dont like!

 

[MikeCO]

Thanks all, getting the shower soon so will be able to see in practice how it all fits out. I hear the points on the custom shower, the reality is that for cost/simplicity reasons with the curved shower model, is that it is much easier to use the prefab (outside of this drain issue). Right now, am leaning towards using an offset drain like this which should have enough space to get past the joist, with potentially just a bit of chiseling on part of the top of the joist: https://www.oatey.com/products/oatey103-series-offset-shower-drain-receptor-base-1301469814.

 

[Jadnashua]

FWIW, when you remove some from the top or bottom of the joist, you effectively make that joist the equivalent of the remaining depth. The two parts of the joist that are the most effective at supplying support are the top and bottom. When you try to bend it with an applied weight, the bottom stretches, and the top compresses. That only works when they're intact. The middle is mostly there to keep the top and bottom in place...picture an I-beam, or a truss that can have lots of open space in the middle. That's why code only allows holes in certain places in a joist, and then, only up to certain diameters and not within a certain distance from the end where it may have to deal with compression to a beam or support wall.

 

[Jeff H Young]

Thanks all, getting the shower soon so will be able to see in practice how it all fits out. I hear the points on the custom shower, the reality is that for cost/simplicity reasons with the curved shower model, is that it is much easier to use the prefab (outside of this drain issue). Right now, am leaning towards using an offset drain like this which should have enough space to get past the joist, with potentially just a bit of chiseling on part of the top of the joist: https://www.oatey.com/products/oatey103-series-offset-shower-drain-receptor-base-1301469814.

Ok well your good to go. you could notch the bottom of the studs where they meet the pan and shove it back a bit 1/2 inch or so easily . Id make a hole in cieling below and hook it up from below. Otherwise you have to set trap exact and the tail piece going up and then quickly glue it all up and throw pan in place.

 

[MikeCO]

Ok well your good to go. you could notch the bottom of the studs where they meet the pan and shove it back a bit 1/2 inch or so easily . Id make a hole in cieling below and hook it up from below. Otherwise you have to set trap exact and the tail piece going up and then quickly glue it all up and throw pan in place.

Curious on this one, since I was thinking through this as well. What would prevent me from dry fitting to figure out the right rotation of the offset drain, and then cementing the bottom part of the drain to the tail piece in the right orientation before installing the pan + top of the drain that screws in? Seems like that could help prevent having to do everything perfect with setting the pan and glueing all at once.

 

[Jeff H Young]

Curious on this one, since I was thinking through this as well. What would prevent me from dry fitting to figure out the right rotation of the offset drain, and then cementing the bottom part of the drain to the tail piece in the right orientation before installing the pan + top of the drain that screws in? Seems like that could help prevent having to do everything perfect with setting the pan and glueing all at once.

usualy there is a big nut on bottom but this one screws in from top like a tub so your idea will work

 

[MikeCO]

Following up with a few pictures - I cut off the copper pipe and added a shielded coupling. Dry fitting, it looks like it will work okay since I'm adding a 3/4" subfloor + a 1/2" wood underlayment. One question I have - as you can see from the second picture, when it's in position, the flat part of the drain rests directly on the joist. Is that going to cause issues with rubbing? Do I need to chisel a bit from the joist to avoid this? The shower pan is going to have mortar underneath it so not expecting it to flex much but not sure if it's an issue if the PVC drain is directly in contact with the joist wood.

 

[Jadnashua]

You REALLY want the riser to be perfectly plumb, or the drain won't be level in the shower. That can make for a really ugly cosmetic effect, and will cause the drainage to be weird if it has to go around the drain to the low side to actually get in.

Keep in mind that dry fitting PVC (or ABS) fittings means the final position will be off. In most cases, you cannot insert the pipe into the fitting all of the way until the cement melts the plastic. The socket is slightly tapered, and the bottom is smaller than the dry pipe so it won't fit, or if you do wedge it in there, you may not be able to get it out again easily. Depending on the diameter and the particular fitting, that can make as much as an inch (less with smaller diameters) between dry fitting and actually solvent welded together. It can ruin your day if location is critical...you need to measure carefully, and cut accurately for it all to work.

 

[Jeff H Young]

You REALLY want the riser to be perfectly plumb, or the drain won't be level in the shower. That can make for a really ugly cosmetic effect, and will cause the drainage to be weird if it has to go around the drain to the low side to actually get in.

Keep in mind that dry fitting PVC (or ABS) fittings means the final position will be off. In most cases, you cannot insert the pipe into the fitting all of the way until the cement melts the plastic. The socket is slightly tapered, and the bottom is smaller than the dry pipe so it won't fit, or if you do wedge it in there, you may not be able to get it out again easily. Depending on the diameter and the particular fitting, that can make as much as an inch (less with smaller diameters) between dry fitting and actually solvent welded together. It can ruin your day if location is critical...you need to measure carefully, and cut accurately for it all to work.

Real good points he should be ware of Jadnashua. Might need to just nick a bit of that joist to get it plumb and level. It looks like trap is 1 1/2 " ? it will work ok but not what inspectors want. but a few adjustments and youll be good. And of cource dry fit is never exactly the same but close

 

[MikeCO]

Thanks for the tips here - will definitely make sure I'm measuring and gluing as I go and keeping the riser plumb & level. Thankfully it's a short section I can redo if things aren't lining up for me. It is a 2-inch P trap, it must just look different in the photo.

 

[wwhitney]

If you need to put a 1/2" chamfer on the top edge of the joist, that would be no problem. Plenty of graded lumber comes with that much wane on it.

Cheers, Wayne

 

[Jeff H Young]

Great your good to go! dont be afraid to knock the corner off the joist just dont go crazy

 

[Jadnashua]

FWIW, most of the strength on a joist is on the top which is in compression and the bottom which is in tension...cutting into either side effectively makes the joist the equivalent of the end, resulting depth. The middle just holds the top and bottom in place for the most part. That's why you can put holes in the middle but aren't supposed to do anything to the top or bottom.