3 piece shower drain base slightly unlevel-due to subfloor

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Carpentersville, IL. Kane County
I've lurked around for several years on this site finding answers to a lot of my questions here. This site, and you people are an amazing resource; thanks in advance for any advice you can provide. This will be my first post.

I have read several posts already about out of level shower drains. But most of those posts seemed to be focused on the plumbing itself needing a modification. In my situation, I have plenty of play in the shower drainage piping (PVC). But my drain base is supposed to be screwed to the floor. My floor is not level at the drain location so I'm weighing my options...

I'm building my first shower. I've got a solid, but uneven subfloor. The original subfloor is 3/4" thick, ~2" wide tongue and groove planks. Throughout the entire house I've screwed down any loose planks and added a layer of 3/4" tongue and groove plywood on top of the planks. This leaves me with a uniform height throughout the house and an overall 1.5" of thickness. The floor is solid.

The house is over a crawlspace and is about 24' from front to back. Running down the center, the interior ends of the floor joists are supported by a large beam. My shower will be positioned over the beam, with my drain just slightly offset from it. This beam's location creates a situation where to the left of the drain, the floor breaks slightly down and to the left, to the right of the drain, it does the opposite and breaks down and to the right. It is also slightly unlevel from front to back-dropping slightly from the curb to the back wall.

I am using the pre pitch system by goof proof. It comes with long plastic wedges that you place on the subfloor with the thin ends closest to the drain and the thicker ends resting at the walls. The wedges have the appropriate preslope angle built in and are affixed to the floor before the first mortar bed goes in. The wedges are basically just an aid to assist you in screening the correct preslope into the first mortar bed.

I have found the highest spot within the shower footprint. I went around the wall and marked where each wedge would rest. At each location I placed a piece of wood with a thickness that would give me a level surface if I laid my level across the wood scrap and the highest point within the shower (these pieces range from 1/8" to 5/16" thick). This ensures that the bottom of my wedges will all be at the same height and will ensure that my preslope ends up correct. As far as the preslope itself, the uneven floor is not that important now that my wedges are all sitting on a flat plane.

But my problem is the shower drain itself. It is glued to the ptrap riser already. The base is made by oatey and is intended to be held down by 4 screws. When I screw it down to my uneven subfloor of course it ends up out of level. I don't believe the piping itself needs a modification because I have enough play to get it to read level all around when it isn't screwed down.

I would appreciate any tips or tricks beyond the following 2 thoughts that I have in my head now...

1) when screwed down, my spirit level reads up to about 1/4 bubble out in some directions. Is it possible that this is acceptable as is?

2) I've considered using a self leveling cement in about a 1' square around the drain. I could lay down a square of plumbers putty, build a square form, temporarily lift the drain about 3/4", lay a snake of plumbers putty around the hole in the subfloor, and then try to apply the self leveling cement inside the form. After it dried, I am picturing that my drain would have a level surface to be screwed to. Then I could install my preslope and make sure to tightly pack under the lip of the drain. Then I could install my liner and my final mortar bed.

What amount of out of level is acceptable for the drain to function properly? I plan to redgard the top mortar bed anyways.

If it seems like I am too far out of level to proceed without making a correction, is the self leveled a good choice? I've never used it before and in such a small area I would be counting on it to flow to level, rather than needing to be tooled into position especially under the flange of the drain. Are there other options?

If the picture shows up properly, you will see my level bubble barely crossing the lines. When I screw it down, it gets a little worse and actually crosses the line clearly.

Thank you guys!


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