How to Build a Japanese Hot Water Soaking Tub

Upgrade your water heater so you are able to run hotter water. Seek a professional opinion, if you plan to install the tub atop your flooring and have concerns about whether it can support the weight. Even a small model built to hold from 120 to 230 gallons can add thousands of pounds when filled.

Identify an area inside or outside your home that has plumbing and electrical sources so you can avoid the expense of moving either or both. Select an area that abuts a wall to anchor the installation. Call your insurance agent to make certain your homeowner’s policy indemnifies you against water damage and liability from a hot tub.

Cut a hole in the floor or deck that approximates the size of your proposed Japanese soak tub dimensions, if you are not installing it on a concrete slab. A typical Japanese soak tub measuring 42 inches square by 42 inches tall should comfortably accommodate one bather immersing himself to his chin. Install a floor drain, interfacing it with your plumbing system. Anchor the water pipe(s) supplying the hot water to the wall.

Frame the walls and floor of your Japanese hot water tub, using five sections of pre-cut, ¾-inch melamine panels screwed together to create the outer shell that forms the bottom of the concrete mold. Buttress the sections with lumber braces. Make a smaller melamine cube based on the width of the tub walls to serve as the interior mold. Use plumbing strap to support a grid of lumber to prevent the mold bottom from sitting atop plumbing pipes.

Pour enough premixed concrete into the bottom of the melamine frame to form the tub’s base. Center and lower the small melamine frame unit atop the cement and fill the area between the walls to create the tub’s sides. Insert a section of PVC pipe into the frame near the top of the tub so it acts as an overflow mechanism, if the water threatens to breach the tub.

Cure the cement according to directions on the cement mix. Remove the lumber braces and melamine framework once the concrete has hardened. Attach hot and cold fixtures to the pipes. If you can locate a faucet unit designed with an Asian influence, it will look right at home. Lower a bench into the tub. Test the unit to ensure everything works.