Cast concrete soaking tub

[splatgirl]

Hi
I'm planning on forming and casting a Japanese soaking tub (Ofuro) from concrete. The tub will sit on a sturdily reinforced slab on grade concrete floor. Dimensions will be 42x42 by ~36" high and the walls will be ~4" thick. (The slab has insulation, PEX for radiant heat and vapor barrier under it in case that matters).

When my plumbers did the under slab rough-in, they boxed out an area under where the tub will eventually sit, leaving what amounts to a hole in the slab where the trap and drain will presumably be brought up.

Questions:
#1. Can I have the plumber install the trap and drain at the appropriate location/height and then pour around them, filling the hole and forming the floor of my tub, or is there a reason these can't be embedded in concrete?

#2. I assume a regular tub drain and stopper mechanism won't work in this situation. A floor drain and flat rubber stopper are fine as far as I'm concerned, but will this meet code? Is there a better solution?

#3. What about the overflow? Do I have to have one? If so, how to do in concrete?

#4. I was told that it's a bad idea to put valves and fixtures directly in concrete because it makes repair or replacement difficult to impossible, so I've planned to locate the fixture in a framed wall that backs up to one of the tub walls. Is there any better way?

Thanks in advance for any advice!

http://www.woodentubs.com/tubs_ofuro.html

[Terry]

The worst problem with a concrete tub, is heating it. If it were a hot tub, it would be constantly heated and ready to use.

Since this is a tub, you will have a hard time overcoming the solid mass of concrete that will be needed to be brought up to temperature.


http://www.arpbathtubs.com/
This is what I used when I wanted a tub like that.
They make cable waste and overflows that may reach high enough.
or in my case, I bent some some copper rod and extend a PP W&O.
You could also use standard glue type W&O fittings.

[splatgirl]

The house is heated with hydronic radiant. Since I installed the PEX myself, I was able to place extra loops under the tub location to keep things warmer in that area. Since the tub will be continuous with the floor, I anticipate the temperature of the concrete structure will remain at or near that of the underlying slab (~80-85 degrees)...one of the many comfortable benefits of the heat-transfer effect of radiant. Hopefully this will offset the heat loss from the water enough to avoid the need for a separate heater.
Were it not for using radiant, I wouldn't have considered a concrete tub for exactly the reason you mentioned. If it ends up that I still lose all the water heat to the concrete, I'll look into one of those ofuro heaters.

I have looked at the tub pictured previously and would consider it as a last resort. Honestly, I think it's ugly and not in keeping with the look of rest of the room/house.

Thanks for the tips on the overflow.
Any ideas to avoiding having a framed wall just for the fixture? I was thinking about the possiblity of a ceiling mount tub filler like Kohler's Laminar, since then i could locate the valve and handle elsewhere in the room (like deck mounted on an adjoining counter) and avoid the framed wall. Thoughts?

[Terry]

You may want to look into John Bridge's tile forum about waterproofing your tub.

There should be any number of attractive ways of supporting a fixture in your case.

[jimbo]

I also had some questions about whether a concrete tub could be made waterproof, but had no experience; didn't want to even bring it up. I bet the John Bridge folks will have the answer.

[jadnashua]

Kerdi could do it (keep it waterproof), but the drain is a problem; they have a prototype version for a tub, but the only current production drain is for showers. That assumes you are going to tile it. Kerdi will only work with a special thinset in drain; no clamps. Comes in either an abs or pvc version to connect to the line. Kerdi is a waterproof membrane with an attached fleece thatyou thinset in place. Overlap by at least 2", and you've got a guaranteed waterproof layer you then tile over.

[master plumber mark]

I am wondering about the wood and how it

keeps from getting moldy over time,

also how do you keep this clean and tidy looking


In the links,

it is basically something a public bath something
like a common hot tub from what I read.

What does it take to keep this clean after draining the tub??

[hj]

If your tub is like 95% of the ones like it in Phoenix, it will only be a short time before it becomes a decorative planter. Usually after it is used a couple of times and you realize how uncomfortable it is with the vertical sides, square corners, and flat floor. If it not so much a question of repairing the valves if you put them in the concrete, but that it would be illegal to mount them below the rim of the tub.

[Bob's HandyGuy]

Far be it from me to abet someone who thinks Terry's tub is ugly and something that resembles a horse trough is not, HOWEVER..... I've got 60 year old concrete laundry tubs that still hold water. (Wouldn't that type of surface be a bit abrasive, if the concrete were finished rough, or slippery if finished smooth?)

[master plumber mark]

I thought about that abrasive bottom too

I wasnt sure if this "hog trough' had a wood bottom

to it or a concrete bottom.....
-------------------------------------------------------

it certanly isnt going to be a place where

you and your girlfreind are going to frolick for hours in...

skinning up knees, buttox , shoulders ect....



I dont think this concrete box is
going to be very appealing to the opposite sex either,

maybe one time , but never again.....
(unless they like it rough.)

its certanly not going to be a "chick magnet"
if you know what I mean..


Terrys tub is a far , far better choice for my money..