I'm still in the concept part of planning a project and there are a few things I need to know about for my bathroom. First I'll explain a bit about the house - the floor of the house is going to be about 4 ft below grade, so basically half the walls and floor will be poured like a basement but with all the plumbing and radiant heating system in the slab. Most of the floors will either be tiled or left as concrete. There will be insulation completely under and around the entire foundation. I'd like a custom concrete tub built into the bathroom. My questions are:

Should the tub be poured with the foundation, shortly after the foundation, or well after the foundation has cured(60 days)? Would the tub cement be different than the foundation cement?

If I want radiant heating in the tub the same as the floor(assuming this is possible with the radiant heating system) can I just leave the loops of tubing for the tub sticking out of the slab and incorperate them when the tub is poured?

Will I need any sort of water proofing or membane inside of the tub? Like say pouring the outside/base then adding a membane connected to the drain and bringing it up over the edge of the outside then just tiling over it when the whole thing is finished; and pouring and forming the inside of the tub separately? Does this idea have any flaws? I understand the tub would be insanely thick-that's OK. It should probably match the 2 1/2ft walls anyway.

What sort of plumbing should be used that will be OK being permanantly embedded in the concrete? That wouldn't leech chemicals into the water?

Thanks.

There is actually a science and a method to using concrete for plumbing fixtures and I've seen just as many failures as I've seen successes.

You might want to consider contacting Jon at Dogpaw design in Seattle for a few pointers before going too far on this project.

I've installed a number of his pieces over the years and never once had a problem with any of his fixtures.