Locating shower drain under slab

[Jim S]

Hello,

Still doing the same bath remodel on our first floor slab. I have a hole open in the slab so I can run the drain from the shower before I close it up. I don't have the shower pan yet. So when the pan comes, I plan on fitting it in the space and seeing where the drain pipe will have to come up through (it's in the middle). Then somehow I have to connect all of the PVC drain pipe pieces and have it come up in the EXACT right spot so that it lines up with the shower pan, then place the pan in position and connect it all up.

My question is how will I get all the joints exactly right so that it comes up at the right spot? If I'm off even 1/4" I'm guessing it won't connect to the drain on the pan. Even if I mark the location somehow it would be hard to do. I won't be able to move the pan much at all since it is captured by three walls and not much room to move.

What I thought might work is to use one or two fernco couplings in the drain piping to give me some adjustability. First off, would this be acceptable? I'd rather not but I don't see any other way. Any ideas?

thanks

 

[Jim S]

Ok well maybe I answered my own question. After some googling I found this great video:

Sounds like a great idea. Make a locating template with cardboard or even 1/4" plywood and use that.

 

[Sponsor]

 

[Michael Young]

Hello,

Still doing the same bath remodel on our first floor slab. I have a hole open in the slab so I can run the drain from the shower before I close it up. I don't have the shower pan yet. So when the pan comes, I plan on fitting it in the space and seeing where the drain pipe will have to come up through (it's in the middle). Then somehow I have to connect all of the PVC drain pipe pieces and have it come up in the EXACT right spot so that it lines up with the shower pan, then place the pan in position and connect it all up.

My question is how will I get all the joints exactly right so that it comes up at the right spot? If I'm off even 1/4" I'm guessing it won't connect to the drain on the pan. Even if I mark the location somehow it would be hard to do. I won't be able to move the pan much at all since it is captured by three walls and not much room to move.

What I thought might work is to use one or two fernco couplings in the drain piping to give me some adjustability. First off, would this be acceptable? I'd rather not but I don't see any other way. Any ideas?

thanks

First, dry measure. mark the perfect center. make marks on the concrete about 3-feet. you want to make a BIG X on the concrete to mark the perfect center. Break the concrete for your mark at perfect center (now your mark is gone - which is why I told you to mark the concrete about 3-feet from center in all directions. You're going to break a hole in the floor and you're going to swing that trap and the riser aiming for dead-center.

when you're done, you'll have a trap and the riser will be sitting at dead center.

now dry fit your drain and take a measurement from the concrete floor to the inside of the drain fittings. Measure three times before you cut.

now you can cut and glue the shower drain onto the riser so it lands at te perfect height

slide your shower stall into position. now putty up the top side of your drain and screw that sucker down.

don't be afraid to measure and re-measure and ask your friend to measure. Good measurements helps this job significantly.

"If I'm off even 1/4" I'm guessing it won't connect to the drain on the pan"

...your pipe will have a little tiny bit of give. so you should be able to push it a little left or right to make it all fit up. You got this!

 

[Jadnashua]

You want your riser to be plumb, which makes it more important getting everything centered properly.

Also note that many of the shower receptors may need to be bedded in mortar to prevent them from flexing and to help ensure that they are perfectly level.

Keep in mind that you cannot reliably dry fit the drain pipe...the sockets are tapered, and you can't get the pipe fully inserted until you add the cement which literally melts the surfaces and lets it properly bottom out. If you just dry fit, your end position WILL be incorrect. Careful measurement with the socket depth should get you very, very close, though. When you backfill the hole, that will help to hold things where you want them to be.

 

[Terry]

I'm with Michael, use a tape measure and make your marks. I have never used cardboard to mark anything. Maybe it helps some people.

That's a pretty large ring for a construction worker to have on the job site. I gave up rings years ago. I don't want to lose any fingers.

I take two measurements, from the long side and from the short side. I install the trap to be centered to that. Michael mentions marking to the side. Yes, for sure. It makes it easier to eyeball the thing.
After the trap is in place, you can drop the pan down make make you vertical measurements. Pull the pan back up and make up that last joint to the trap. Now you're ready to drop it for real. You may need (want) something under the pan depending on how if feels.