Shower pan install plumbing questions

[rippie]

I can't say enough about how not having the subfloor template has factored into doubt about many aspects of this work. I realize as I go to dry fit my shower pan to subfloor, I am not sure of the correct placement of materials. If I had a template with proper hole size, I could more easily figure it out. As it is, I cut the hole for the shower drain to match the size of the hole in the pan. I did not take into account for the gasket and securing nut for the drain. I figured the p-trap should remain flush with the bottom of the ply.
My intuition is that I need a bigger hole to allow for the gasket/nut to directly secure the drain to pan. Then the pan could sit flush and the p trap would attach to the threads of the drain that protrude beneath the floor. Just want to make sure before I do any cutting. Right?

[Del Gurney]

I replaced my drain in the shower as part of a under carriage refit. Only because it was a little pitted and it seemed like a good time to do it (considering the pain of dropping the alu-sheet metal.
A couple things. The new drain should come with instructions. If you are using an old one then I would cut a hole in a sample piece to make sure before I destroyed the new pan.
The p-trap (as you said) must be as high as possible....the top of mine is flush with the sub-floor.
One other thing.....I introduced some high density foam pieces between the pan and sub-floor so the pan does not flex when I'm standing in there. Heavy people can crack the plastic. Good luck

[rippie]

Del-
My pan has a corrugated-like support piece adhered to the bottom. Do you mean you placed foam inside the ridges for extra support? Not sure what you mean about cutting a sample piece? A sample of subfloor to check the fit? And I am using the old drain. My main question is should my subfloor hole be the diameter of the drain lip/gasket (see picture).
Did you do any other work while you were in there? I will be finishing up soon(hopefully), but going back in for a grey tank addition later.

[rippie]

Well I have slept on it and not really closer to figuring it out.
The drain lip (above shower pan) and the p-trap diameters are the same. So I feel I should not cut the hole to that diameter, because I will lose that opposing tension that would help secure the pan to the floor. But there is still the gasket/nut that secure the drain to the pan. The only solution I see is routing out the subfloor hole at the top to make room for the gasket and nut. I feel like I am missing something. I am just being cautious because I don't want to have to try to add back to the floor if I make a mistake cutting.

[Minno]

Rippie,

The drain nut should NOT try to secure the shower pan to the sub-floor. Doing that is asking for the shower pan to crack while driving down the road, and for it leak a lot around the drain.

The pan should be secured to the sub-floor using caulk/sealant designed for installing tub and shower enclosures. 100% silicone would be a good choice for gluing the shower pan to the floor. The drain nut should be tight to the bottom of the shower pan itself. The top part of the drain should sit on top of the shower pan. Most shower pans have an indentation where the drain sits, allowing the top of the drain to sit level with the rest of the shower floor. This allows water to drain completely out of the shower. Use plumber's putty under the top lip of the drain so it seals the upper part of the drain to the shower pan. The rubber gasket goes underneath the shower pan, and is held in place with the nut. Tightly snugly, but do not overtighten. The goal is too squeeze most of the plumber's putty out, but not all of it. Plus, you don't want to crack the shower pan. Once tight, the drain should feel secure to the pan, without any side to side movement. The hole through the pan should be just big enough for the drain to fit through.

Off the bottom of the drain, you should have either a really short piece of threaded pipe that will connect the drain to the p-trap, or the p-trap can be directly connected to the drain threads. The p-trap may sit below the sub-floor, which is ok. This means you need to enlarge the hole in your sub-floor enough to allow the fitting on the p-trap to fit. That probably means enlarging the hole by another 1/2" or so.

But, where is the drain pipe located? Is it also under the sub-floor? Or is it sitting in top of the sub-floor?

Chris

[Del Gurney]

Chris is right. Chris's last question is something I had not considered as I was only replacing the drain (not a major refit like you).
All I know is you want a good flow with out right angles etc. The distance from the drain to the top of the tank will not be much..the bottom of my p-trap is only 1" above the top of the tank.
When the tank backs up...so does the shower pan...that when it is past time to dump the tank.
As for support of the pan: I only had access to see a little bit through the sub-floor cut out for the drain. So I just inserted high density foam "by feel" with a flash light and a mirror.
Get'r done
Cheers.

[rippie]

Thanks Del and Chris. These were very informative responses. So I completed the install. I decided to cut the hole in the subfloor big enough for the locknut to fit in, but small enough for the lip of the p-trap to make contact to the sub from below. I left the gasket above the nut for a little cushioning above the subfloor. As for drain lines, I reused the old ones. These grey lines merge to one and join the tee below the black. My black tank is above floor and I have had it back up from overfill
I also completed repairs to a broken abs elbow and plumbed to my gate valve. I tested it all today as it took me some time to complete pex to the point I could turn on water. Unfortunately, I had a drip. The elbow downstream from the one I had just repaired had a hairline crack. So now I will need to repair it. The worst part is that it looks to me that I will have to repair a few neighbors that are closely connected. The 22 1/2 on the left buts up to another 22 1/2. Then they but right up to that wye. No space for a coupling anywhere. I have now done a few abs repairs, but is there any way around replacing all the other stuff? I kinda feel that a fernco connector thrown in the mix here would do good to relieve stress on these elbows as I have had to repair two elbows upstream from this one. I may post this issue as a new post if no response. Any expert shortcuts?
Ok. Not sure what is happening here, but my photo got rotated a quarter turn counterclockwise. This keeps happening and I don't know the reason or the fix. It is normal on my phone and even the initial thumbnail once downloaded is properly positioned. But then it appears in the post sideways. And I don't know how to correct it from there. Another thread topic, I guess.

[Minno]

Rippie, they do make a drill attachment that will let you drill the pipe stub out of a female fitting, but with those fittings so close to the wall, you'd have to remove them all in order to drill them out. ABS fittings and couplings are pretty cheap, so I'd remove both 22 1/2's and the wye and replace them all.

No answer for you picture rotation problem. One of the moderators can problably help with that.

Chris

[rippie]

Chris- good news to report and something that will most likely be helpful to some. Due to your mention of a cut out drill attachment(thanks, by the way), I decided I would consider it. Called HD. In stock about 10 bucks. So I looked for a you tube on it. Found one, but the guy also showed another technique where you score the inner ring of the pipe remnant you want removed from the hub of the fitting you are trying to reuse. Then you chisel between the two all the way around. I used a dremel type tool to score in a cross. Then I removed each section one by one with a rubber mallet and thin flathead. Had it out in minutes. I used a grinder to remove the broken elbow to allow me to get to the good one. I was able to remove the rest of the vent stack due to a fernco abt 6 inches above floor. So this little technique saves me from having to replace another elbow and that tee. I ordered the elbow, 10 ft of 1 1/2 ABS, & some ABS glue. Unfortunately I have to wait til Tuesday to repair. Aaand, once again, picture tilted, but hard to tell on this one.