Chosen Solution
I have a Pixel 3 XL a family member broke the screen on, so I bought a donor phone to get the screen and got the phone going and it worked out well (outside of ripping the matched camera on one side, and fingerprint reader but since I was working with a donor device heh), didn’t even have to recalibrate the finger sensor because I reset it and never touched it until I could confirm it works. They didn’t want it back, so free phone (well, outside of needing to buy a parts phone). Is it possible to restore the water resistance reliably on these, or should I consign myself to no water resistance and just seal it well enough to close (but be serviceable) once I replace the battery? The battery I put in was bent in (pulled from the donor) removal a little, but it worked for testing.
Once you open it that’s it. All you can do is to reseat it with tape or glue, then keep it dry. Glue if applied correctly will give a better seal.
Even with an original seal, there really isn’t a 100% waterproof phone, if you search Pixel 3xl back housing seal you will find some with the same shape and size as the original, i woud recommend using a proper seal made for your phone model because doing it by hand with double sided tape will often leave gaps in the corners where dust and liquid can come through. Honestly just closing it well enough with tape or glue you have should be fine if you are the one using it, but like i said, phone are not waterproof.
