Access to slip fittings

Hey, great site Terry. Found you over at the JB tile forum.

I'm a tile setter being asked to permanently cover over access to some plumbing fittings that concern me. It's the p-trap, drain, & overflow for a large fiberglass tub where they used all slip fittings, no cement. This is all the thin white plastic that are the same as under a bathroom sink, not sched-40.
I thought finger-tighten fittings or thin-wall fittings would need access to them because I see them leak so often? Is there anything in the UPC or is it just in the IAPMO installation standards (which this city doesn't subscribe to)? Thanks!

- Tom Hulse
Hulse Tile & Stone

slip fittings

They leak under sinks because they can move. Behind a tub they are rigid, so they do not leak and they do not need access.

Thanks hj. IAPMO Installation Standards IS5-314.1 seems like it says they need access, but do I understand right that most cities don't subscribe to all the Installation Standards section, so access would be recommended but not required?
This is for a fiberglass extra large 2-person tub that is raised up off the floor. The manufacturer's support system is good at the two ends of the tub, but the middle is unsupported where the drain is. I wouldn't say it has no movement there, especially filling up & then draining a zillion gallons of water. The 2 end "feet" are correctly supported with a little mortar.
Thanks for your time.

It depends on the city or inspector.

Most codes have changed to require glue joints on tubs.
However, there are still some that let you use slip joint on the large tubs.

Thanks for the response Terry.
Looks like I'll be spending next week on a tile job in your hometown.
Keep up the good work, I love your site.
- Tom