Stall shower above slab

[smithy]

I am currently remodeling a 50's ranch house in Savannah, Ga. Part of this is converting a 1/2 bath into a full bath by adding a stall shower. I have an idea how I would like to run the shower plumbing and would like some feedback on whether or not it would work and ask a few questions. Here's the synopsis:

I have a slab foundation with no drain provisions at this location so I need to tie into another drain. The drain stub up for the washing machine is on the other side of the wall and I was considering tying into it.

Will this work? Do I need a trap for this drain or will the trap for the existing drain work for both? That drain ties directly into the main stack with a trap about a foot away.

Also, I am planning on installing the shower pan on an elevated platform in order to create space above the slab for the drain. I've seen this done and it is a little awkward but seems necessary in order to get enough slope for the drain.

The water supply is a little bit easier since I will be able to tie into the supply lines for the vanity sink on the adjacent wall.

Oh, one last thing. All of my pipe is of the galvanized variety except for some of the new PVC I added to run a drain in the kitch.

Thanks in advance for the feedback. Sorry for the wordy thread.

[Gary Swart]

Putting a shower stall on a platform is considered to be quite tacky. You should consider that you will have to live with this for as long as you live in the house. All drains must have there own trap, so yes, the shower must have on. Also it must be vented. The drain must be 2" and have a 1/4" per foot slope. This means cutting a hole in the slab to accomodate the trap. The shower drain has to be centered on the stall.