The Reverse Hot Tub / Luxury Ice Bath

In this instructable I'm going to show you how I made a Reverse Hot Tub aka an Ice Bath.

There's been a lot of people that have built ice baths or reverse hot tubs using just a chest freezer but it just looks like a freezer. I wanted to make a luxury reverse hot tub. Something you'll be happy to sit in everyday.

The first thing you gonna need is a freezer!

People give away the craziest things. I found this one for free online. You just have to have a little patience.

Did it work? Yeah it works awesome but it didn't have a lid. That didn't matter as we were going to to make this thing look not like a freezer and build our own lid too.

I modified the interior because I did not want it to look like a freezer.

Because my freezer wasn't even on all sides the first job is to make sure that all the sides are even. I did this by fixing metal coping around the edges and built up the side with some wood. The metal coping was cut using an angle grinder and fixed in position using some pop rivets.

The excess coping was cut off so all sides were now even. Any air gaps were filled with expandable foam. Once this had cured the access was then cut off.

We have to seal it because the freezer is not a pool and it's not designed to hold water.

To seal the freezer I used water proof silicone. Ensuring all corners and gaps were completely filled.

Remember the freezer is going to get very cold and the Silicone will shrink. So you need to make sure that you use it liberally, otherwise the freezer will leak.

Just like a normal pool you need to circulate the water. This prevents bacteria build-up. Along with filtering of the water. In addition it also limits the amount of water freezing inside. As moving water is harder to freeze.

The first thing you need to do, is to work out where your refrigerant pipes are NOT. If you cut a pipe and let out the gas. Its game over for your project.
I was extremely lucky. Barely missing a refrigerant pipe as I drilled the hole in the floor for the pump suction. There is no sure way to know where all the refrigerant pipes are. A trick I learnt after, was to run the freezer and spray misted water around. You’ll begin to see what freezes. Indicating there is a refrigerant pipe there. You must also be careful of the condenser. Most chest freezers have the condenser in the outside walls. You can check this by running your hand along the outside walls to feel for heat. Where there is heat there is the condenser.

I drilled the suction and discharge holes at opposite ends to ensure the best circulation.

Your suction pipe is the most important. It's important because this pipe is mounted in the bottom and can not leak.
Because I drilled my hole so close to the refrigerant pipe I had to move the hole slightly and a place a new bottom 1 mm aluminum plate. As you can see in the picture. I used bathroom fittings as all the PVC pipe fit perfectly together with these fittings. I insulated the pipes using pipe insulation to insure minimal cooling losses. Any gaps were completely filled up with foam to ensure there was no possibility of condensation build up.

The Pump its self was just a cheap above ground pool pump which I mounted next to the compressor. This would later be hidden by the stair I built later.

For the top coping we are going to mitre some 1,5" by 62 impregnated timber at 45 degrees to make a perfect frame

Mitering wood can be difficult especially if you don't have a accurate saw. So when you eventually get it right it's important to rock out to celebrate.

Once you're happy with your miters use it a biscuit cutter to insure they line-up and screw together using a pocket hole jig

I will show you how I fastened it down in a later step.

For me the most important thing is that this does not look like a freezer. So cladding and making this little step, to me, makes this feel luxurious.

I made no formal drawings. Just this ridiculous doodle.

Because the condenser is on the outer wall of the freezer we need to leave a small air gap so the heat can be expelled. I used 1” x 2“ listing, then screwed the cladding to this. I ensured a 10 mm gaps between each board and left a 1-inch gap at the top. The stair was constructed with 2x4's With the stair built high enough to house the circulation pump and allow access to the compressor and thermostat approximately. The aim was the stair could be removed to get access to the circulation pump and the compressor if need be.

Feel free to use your artistic interpretation here. Do what works for you but always consider the engineering side.

Before fastening the top coping we need to ensure there is a seal underneath. I used a thin foam mat on the under side. It was a little like a yoga mat. I stapled it down with a 10 mm overhang. This is what the lid will seal against and this will stop the cold air from escaping.

To fasten the top coping drill down through the top coping into the vertical listings that the cladding is screwed to. Insert a blind nut or whatever they're called. Then use a M6 100mm Allen head screw to tighten the top coping and ensure the seal is tight.

This was probably the most challenging part. Doing all the mathematics to make sure this was going to work. I built a prototype to ensure the concepts worked then cracked on. The idea is that the lid hinges in on itself so that the outside cladding looks nice when you're sitting inside and you are not staring at ugly insulation.

I recessed the hinges into the center join then built a framework using 1" x 2" listing around this. Once I was happy with the framework and it functioned as it should. I insulated the top part using 50 mm polystyrene and sealed the top using a waterproof underlay. I used asphalt glue on the underside of each board on the top. To ensure that the water did not sit underneath the cladding and cause problems in the future.

To control the temperature I used a thermostat which was programmable to set the desired temperature.

I am not an electrician so please do not do this yourself if you are not sure. I wired in the thermostat after the power switch. The thermostat will close the switch to the compressor and circulation pump when the temperature rises above the set temperature. The compressor and pump will run until it reaches the set temperature and then the thermostat will open the switch stopping compressor and the pump.

Because there is water involved be sure to completely seal any electrical components so that no one gets hurt.

Again I am not an electrician so please be sure to check with a professional before attempting anything like this.

The last step is to fill it up with water and enjoy.

Be sure to check for leaks and that it's functioning properly before jumping in. I would highly recommend switching it off before jumping in.

I also dosed the water with chlorine to ensure it stayed as clean as possible for as long as possible. One thing to note is... Chlorine reacts with the aluminum. So be sure if your freezer is lined with aluminium to control the pH level carefully to avoid corrosion.

Now it's time to freeze your balls off and enjoy the therapeutic benefits of of ice bathing

Thanks for reading :)