Tips for Replacing Shower Pans
When the shower pan is sitting on the ground, any side that touch the wall there's an one 0.5" lip that flare upwards to stop leaking into the wall and to mount the shower pan to the studs. On the wall if its tiles you're taking out the first row from the bottom.
Mark 2" along the pinnacle of the shower pan, cut it away and unscrew the mounting bolts from the studs. If you can not disassemble the old drain from the pan, drill a 1" hole by the drain, use the jig saw and cut round the drain. Pry the pan up from the floor and take it out.
Looking at the drain if you've a slap floor you must have a dry well for the drain line, if you have got a crawl space you have to go under, dig out some of the dust and cut the drain line to fit a coupling on the new extension without the new shower pan drain touching it when its installed if the drain line is solid iron you could have to chop the shower drain with the jig saw on both side (splitting it in 2) to take it off the line.
Before putting the tub down, extend the drain up pipe if you cut it. Measure from the distance from the floor to the apex of the shower pan drain then take away 0.5" and cut the drain line.
It's always better to try fit all of the connection before last glue down or tightening. Mix up some cement mortar mix and spread it 6" around the fringe of the drain's dry well. You only need perhaps 2" thick ring of mortar cement. Step and push the shower pan down till it sit flat on the floor. Within the shower drain there's suspect to have a rubber seal between the drain and the drain pipe, tighten the seal in with the seal's nut. Now you can mount the shower pan to the wall with screws, patch the dry wall back, reinstall tiles.
