How to drain a free standing bathtub

Question

I have a freestanding bathtub to be installed on a bathroom with concrete floor that will be tilled.

There were no instructions with the bathtub and the company doesn't really care (Brazil has terrible customer service for some stuff). The drain points straight down and is 40mm in diameter.

I can't use a 90° bend because that would press against the floor because the height will be greater than that of the feet.

I can try to drain directly below, but I'm not sure what is the best course of action. Have a standing pipe just a bit larger than the bathtub drain pipe for the bathtub drain to slide into? Making it some what hard fixed into the floor.

Have a shorter standing pipe (some 30 mm above the floor) the same diameter of the bathtub drain and use a rubber union to join then? More flexible, less chance of some breakage.

Have a dry floor drain (100mm diameter and some 50 mm deep) just below the bathtub drain and make it drain to the shower trap? Greater flexibility on positioning, but will it overflow?

What do you suggest in this scenario?

Answer 1

First & foremost you need a Freestanding Tub Drain Kit, no regular piping will work. These drains are extremely tight 90's & will leave space above the floor.

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Then, you need either a trap in the floor of the drain you have available in the area where you want the tub. If there's no trap & you'd rather not rip up the floor. Then, you can put the tub on a platform for just the tub or for that whole side of the bathroom. This can also allow you to face the tub in your preferred position.

Answer 2

If it where me I would install a narrow drain in the tub with a lint filter in the bottom given you have a wet room. I have seen this in France and it honestly is quite useful. It is virtually impossible to cleanout a pipe well that is stuck in concrete so getting things before it goes down makes sense.