Answering this question leaves a lot of unknowns; 1) Is this in the basement, in the floor, under concrete, or, going to be. 2) Is this on a main level, above a basement (Not a crawl space!). And 10 more questions! There is some planning, but, could be trying to answer 25 different scenario's, as much supplied info. will help. For a short answer to keep it simple, the answer is, yes, you can!
Everything the same as when only setting up one, however the drain farthest away from where the two meed the drain line must be slightly higher (1/4 inch high per foot of distance to the other drain (or more)and you will have two vent pipes (one from each) that can be tied together and sent out through the roof. Also don't forget you need two traps (one for each right under the drains).
1/4 inch per foot.
Probably the wrong size flange. Is the flange a toilet collar? If so the pipe is probably 4 inch.
One eighth inch drop per foot of run.
Wouldn't recommend it as things may back up in the drain line. 4" line is the norm ... you want to get rid of waste, not keep it around longer.
1-1/2 inch drain for above grade and 2 inch drain for below grade. Most UPC-based codes (IAPMO) require 2 inch above and below grade.
A shower drain is 1 1/2 or 2 inch and a toilet needs to be either 3 or 4 inch.
Possibly a caulked joint ( lead and oakum )
A fernco or rubber fitting. This made of rubber and had hose clamps on it. You should ask for assistance at a hardware or plumbing shop for a 2" Plastic X 2" Copper Fernco or rubber coupling.
Absolutely NOT you 2" minimum
You can use the existing floor drain lines most likely you will have to cut the drain line or add to it to line up with the hole in the shower. tubs have drains on one end while most showers have it in the middle. You can buy a 30" by five foot base from Mustee. Nice product, comes in left or right hand drain.
Everything the same as when only setting up one, however the drain farthest away from where the two meed the drain line must be slightly higher (1/4 inch high per foot of distance to the other drain (or more)and you will have two vent pipes (one from each) that can be tied together and sent out through the roof. Also don't forget you need two traps (one for each right under the drains).
How to Install Mortar Shower Pan Membrane LinerOnce you've framed the shower stall, it is time to install the pan liner and cement backer board to create a water tight seal.Remove the drain cap and tape over the drain to keep mortar and other debris from entering the drain. Put down a layer of felt paper to help prevent moisture from wicking down through to the subfloor. Place a layer of metal lathe over the felt paper. Trowel in a layer of mortar that it has a one quarter inch slope towards the drain. Once the mortar dries, place a layer of felt paper along the walls of the shower stall. Attach cement board with the rough side out along the top half of the walls. Install the shower stall membrane in the bottom of the shower so that it overlaps in the corners, covers the shower curb and is approximately six inches up the side of the walls. Cut out holes for the drain, the drain bolts and the weep holes. Seal the underside of the membrane near the drain with silicone. Nail the membrane that covers the curb only on the outside. Attach the remaining cement board leaving one inch clearance from the bottom. Caulk all seems. Place some pebbles near the weep holes to protect the openings. Trowel in a layer of mortar that has a one quarter inch slope towards the drain. Mortar the curb. Remove the tape from the drain.
Use kettle hot water or plunge the drain with a basin plunger or use a 2 inch spring wire to loosen waste inside the pipe
36 x 36 inch is considered standard for shower stalls.
A 50mm (2 inch) shower waste trap.
There is a main drain that runs from the basement through the roof where it is the vent for the system. If you look at the layout of the house, the upstairs bath is most likely over the downstairs one or the kitchen. If you look on the roof, you will see a 4 inch pipe coming through the roof that should be over the upstairs bath. The sink and shower drain into that and then to the basement and out of the house. Most likely the main stack is in the wall behind the toilet.