Introduction: My Red-neck Wood-fired Hot Tub!
Second Prize in the
3rd Annual Make It Stick Contest
This is a tub I built for my wife after she hurt her back at work and needed somewhere to soak and relieve tension. Our indoor tub is small and didn't work well enough for her to get any benefits of the hot water or the bath spa.
Because we have a limited budget, no truck to transport a real hot-tub, and no one to help me move such a beast, I decided building my own would be the next best thing.
I took as many pictures as I could, but the camera broke shortly after starting this and trying to salvage what few pics my phone could get, I came up with a few to get the general idea! If you have questions or comments, please leave them for me, and I'll answer them as best I can!
Step 1: Step 1. Gather Materials/ What You Will Need:
1.A stock tank- This is a 4' diameter 2' deep round stock tank I found used for $50. (You can use the plastic ones too as they are cheaper if new and easier to cut.)
2.A Chiminea/outdoor fireplace. (we had one already but they sell for around $40 new for a medium to small one at garden centers.)
3.A Bathtub Spa/Jacuzzi -
4.Two ¾ inch PVC faucets/spigots.
5.Two ¾ Male PVC adapters.
6.Four or five ¾ inch O-Rings/Washers.
8.JB Water Weld (for Occasional Leaks)
9.Garden Hose ½ or 5/8 inch – about 20 feet.
10.20' copper tubing (I used type L – about $25 at home improvement stores.)
11.5 to 7-¾ inch hose clamps
12.1 or 2 female hose ends.
13.Fountain Pump (I got mine at a discount store for $10 but as long as it has a 2' lift it should be fine)
14.A Piece of Plywood big enough to cover your tank (You can use other things too if you have them)
15.1 roll of electrical tape.
16. 5 or 6 pool-noodles for padding and/or insulation.(optional!)
1.Drill with 1 inch bit or hole bit.
2.Flat head screwdriver
Step 2: Step 2: Clean Out Your Stock Tank- Check for Leaks
Step 2: Clean out your Stock Tank- Check for leaks
No matter where you buy your stock tank you need to fill it up and check for leaks, as well as clean it. These are usually stored outside and also can have things left over from the factory on them. Checking for leaks is important because you don't want any and even a brand new tank can have one or two – albeit rarely.
Once the tank is full, and if you find a leak, mark it somehow. I usually just put a piece of tape or ark it with a sharpie if I find one. Once you've found any leaks, its time to clean.
As far as cleaning goes, I use a mild dish detergent and a scrub brush. I start draining the tank and wash as the water goes down, until I am at the floor.
Once you are done washing the tank, rinse it out. You can stand it up and just spray it with a hose if you like.
Don't forget to wash the outside as well as it gets junk on it too!
Once washed, go back to any leaks and patch them using the JB Water Weld – or whatever you like to use for water proofing. (I like the water weld because it is cheap, it works, bonds to plastic and metal and cures in an hour.)
Step 3: Step 3: Paint Your Tank
Step 3: Paint your Tank
You can skip this step if you like, but if you are using a used galvanized metal stock tank, I do recommend it. While they are resistant to rust they are not impervious. Also, painting the tank will give any suction cups on your pump or bath-spa a better hold on the bottom of the tank.
I simply used cheap black spray paint I had around the garage to cover my tank. I ran out of black, so I finished it with gold. I did two coats on the inside where there was some rust already and one on the outside where it was pretty clean and won't be in contact with water very much.
When painting with spray paint be careful to stay outside the tank and srpay from a distance. I didn't and not only got a killer headache- but I got paint all over me and my beard came out black like I'd been huffing the stuff! (Very awkward when picking up my son from pre-school!)
If you are using a round tank like I did, I stood the tank on it's side over a tarp and sprayed one area at a time, then rolled the tank to expose more area. If you spray in light coats and move constantly, you won't get drips and you won't get paint rubbed off when you roll it as it will dry fairly quickly.
Step 4: Step 4. Installing the Spigots/faucets
I had the brass faucet I used sitting around but for the other faucet I decided to go with a cheaper PVC model. I chose this because the pressure on it would be negligible & the cost was much less than brass or other faucets at the hardware store.
My tank came with a drain plug I removed with a pair of channel lock pliers. Install one o-ring washer on the faucet then insert it in the hole. Attach another washer on the inside and then put on the bolt/adapter. Tighten it snugly, but don't over-tighten as PVC will break quickly!
The next hole I had to make I chose to install about 8 inches below the rim. To make the hole I used my drill and a ¼ inch bit to make a hole. Next I used the 1 inch hole bit and inserted the center into the pre-drilled hole to make my faucet opening.
(note: don't do like I did and tear through this. Let the bit etch a line in the metal if you have one and then drill again from the inside. Then break out the rest of the hole gently with pliers. I tore through it and managed to make a jagged hole that had one side that tore the metal. - More water-weld for that!)
Once the hole is complete, make sure you can insert your faucet fully. A little tightness is ok, but too much (as well as too big a hole) can cause leaks.
Again, put the washer on the faucet, insert it in the hole, then another washer on the faucet, screw on the adapter!
Voila, you now have two faucets on your tank – which will provide you with hot water!
(Note, as you can see in the pictures - if you look closely- , I had to modify my top faucet because the tear I made was too large and cuased a constant leak! What I did to patch it was cut up a used mouse-pad to fit over the faucet, then screwed that down. Leak stopped and problem solved!)
Step 5: Step Five: Making Your Heating Element
Working with the copper tubing is hard, but if you have a chiminea like I do, then you can pretty much keep most of the coil intact as it comes out of the box from the store, only bending the ends out to attach your hose.
Like I said, working with copper is hard, but go slow and don't over exert your strength and you should be just fine. To bend the copper I simply did it by hand, workin slowing and making small bends to avoid kinking or collapsing the tube.
For smaller openings in small chimineas, you can bend the coil into a smaller circle, or into a spiral.
If you have an outdoor fireplace, you can expand the coil with few problems to either fit around the a fire screen, hang it from the inside top of it, or place it directly around the burn area for maximum exposure.
IMPORTANT: make sure your ends are clear of the area where you will be burning be about 5 to 6 inches! This is usually enough to make sure the hose doesn't melt!
To make my heating element a little better, I bend the coil down to a diameter of about 10 inches. Then I lead one end up and out of the top of the chiminea to hang it from the top and center the coil in the burn chamber. It increased the ability to collect heat, and I Also could put wood inside it to burn and get a better return on smaller amounts of wood!
Step 6: Step 6: Attaching Your Hoses
(At this point you can fill your tub from a regular hose or wait until you are completed with everything, but I found it helpful to make sure there were no leaks when I could turn on the faucet and see right then and it saved time later.)
This next part has a few options to try and I had a lot of trial and error here. If you have leaks, then keep trying things until they stop.
First, grab your hose and bend it in half. Using a sharp knife, cut out a 2 foot section in the middle of the hose. This section will eventually attach to your pump.
If you have a complete hose, you are in luck. If not you need to use two female garden hose ends and attach them to one end of each length of long hose you have left.
Personally I hate the clamps on the ones as they come from the hardware store so I use ¾ inch hose clamps to tighten mine up and make them leak-proof. Once this is done, then move to the other ends of your hoses.
I use teflon tape on each spigot and on the end of the copper pipes to help cut down on water leaks and fill any irregular gaps caused by the clamps and hose on the copper tubing.
Attach one hose end to each side of your copper coil, using the ¾ inch hose clamps. Tighten them down, but be careful not to collapse the copper tubing!
Once your hoses are attached, then end one end of the copper coil downwards a bit, and one end up. The downward end is your cold water hose, the upper one is the hot water hose.
Attach your female hose ends to your faucets on the side of the tub. Cold water to the lower faucet, hot water to the higher faucet. I use the Teflon tape and channel lock pliers to ensure a good leak-proof fit.
Step 7: Step 7. Attaching the Pump
(NOTE: Many fountian pumps are NOT rated to work in higher water temperatures- mine said 90 degrees- so check that out before trying this. My own pump was something I had for a few years and it chugs like a champ in the higher water temps so I used it instead of throwing it or giving it away. You can find spa pumps or pool pumps used if you check around and it might be wiser to try those.)
(SECOND NOTE: I will get to the thermosyphon effect in a moment, so please be patient.)
To make the pump work well with maximum flow I suggest placing the chiminea on a lower area away from the tub, or make sure that your copper tubing is not higher than your top faucet.
Most fountain pumps I have seen come with a long tube to make the fountain spray over the top of the water. I simple detached the small snap ring on the bottom of mine and then attached one end of the 2 foot hose to it using a ¾ inch hose clamp. If your tube doesn't have the detachable snap ring you can attach the hose to the top of the tube, or cut it off with a hacksaw wherever you like, as long as you have enough room to clamp on your hose.
Next, to fit the pump to the inside of the adapter for the lower faucet, I built up the end of the hose with electrical tape. I simply rolled it around and around until I could get a good fit without the pressure blowing it back out.
I wouldn't suggest trying to clamp this or attach it permanently as you can then take the pump out with more ease in case you need to. I take it out quite often once my water temp is reached to keep that temp level and depend on the small about of thermosyphoning I get to keep the temp up.
I've read about thermosyphon heaters and I think they are a wonderful idea. I tried it, and it didn't work very well because I am using simple garden hose and the diameter of the hose is too restrictive. I do get a thermosyphon effect when I remove the pump, but it is so weak that it takes about 8 hours of burning to get the water up to a decent temperature. Instead I went with the pump assist method to speed this up, and I depend on the small thermosyphon effect to keep that temp pretty level once I get the water hot enough.
BEFORE GETTING INTO THE TUB I PULL THE PUMP OUT OF THE WATER USING THE CORD!
THIS PREVENTS ANY ACCIDENTAL ELECTROCUTION FROM A FAILURE OF THE PUMP INSULATION!
I DON'T THINK IT IS A LARGE RISK, BUT THIS IS WATER AND ELECTRICITY SO BE SAFE- PULL THE PUMP, AND ENJOY!
Step 8: Step 8: Building a Cover
To build a cover for your hot tub, I found the easiest method to get one to fit was to turn the empty tank over my piece of plywood and trace the outline around the outer edge of the tub.
I then cut out the wood with my jig saw. Once that was done I had my cover.
You will probably notice the cover doesn't go entirely over the tub. That's my fault because all I had was one sheet of plywood at the time and I use that notch to keep the hose for the bath spa in as well as the cord for the pump.
When cutting the decking for the tub, I recycled one of the round pieces for the missing edge and it gives me a good handle to grap to remove the cover.
To protect the plywood I used and old tarp (already with tears and holes) and cut it out to fit over the edge. I then stapled the cover down on the other side. For the interior I used some insulating bubble wrap with one foil side and glued it down over most of the tarp edges!
You can make a two piece cover if you like by simply sawing your over in half and attaching hinges to it, but I chose to keep mine simple since it wasn't that large.
Step 9: Step 9: Heating the Tub
To heat the tub two things have to be done first to avoid problems.
1.Turn on the pump, attach the hose to the adapter inside the bottom faucet of the tub, open both faucets, and make sure all air is removed from the line.
I let mine run about 4 minutes the first time and made sure I had a good stream of water coming out of the opened faucet on the top.
2.Before starting any fire, make sure you are getting a good flow of water through your copper coil an all hoses are well away from the chiminea or fire-pit! The water will take the heat from the copper tubing and will keep the ends of the hoses from melting.
The next step is build a fire in your chiminea/fire-pit AFTER you have water flowing.
Once the fire is good and hot, let the pump do the work and make sure you have you cover on the tub to retain that added heat. My tub takes about 3 hours to heat to 104 dregrees F. - which is the recommended safe temperature for hot-tubs.
After you have reached your target temperature, I would suggest removing the pump for two reasons:
One, if you even have coals or a small fire, this will keep the water from getting too hot; and Two, you will get a small thermosyphon effect that will help maintain your water temperature.
At this point you can stop and enjoy a hot soak in what is basically a version of a Japanese Soaking Tub. I prefer bubbles in mine
so I continue...
Step 10: Step 10. Adding Bubbles
To add bubbles we use a bathrub spa/jacuzzi to the bottom of the tank.
If you have a large tank and more than one person, you might consider running two of them.
(NOTE: when you set up the Spa make sure that the Spa is placed at a Height ABOVE the highest level of the water!!!!
I can't stress this enough because when you turn the spa off, water will move up the air-pipe and may cause a short, electrocution, or may break the spa motor. Placing the Spa above the water level is a good way to prevent this from happening.)
I have the hard plastic pad with suction cups on the bottom that I put down in the tank. For the tank I am using one spa is enough for two people.
The model spa I have is very powerful and you have to sit on the pad to keep it from floating up, but the jets of air it makes are awesome to feel!
If you add bubbles, you will get a drop in the temp of your Tub so you can keep that in mind when heating it and shoot for a couple degrees over 104 F.
That's basically all there is to this Red-Neck Wood-Fired Hot-Tub! I hose to add some options that you might find helpful in the next step!
Step 11: Step 11. Optional Additions
In making this I had several other options I Chose to add after completion.
The first of these is I added insulation to the outside and bottom of the tank to hold in the heat.
I used insulating bubble wrap and attached it to the outside with Liquid nails and some spray adhesive. For the bottom I cut a large circle and the tub simply sits on this in case I want to do something like add a water-bed heater later.
Next I built a surround for the Tub using deck wood I got for free. It took a little finagling and I finally managed to get it all covered.
I did keep the corner with the spigots accessible by screwing the wood to a triangle of 1/4" plywood. and I simply lay it down over the corner since no one uses it.
(I still have to paint my wood to protect it from the water and the elements, but at this time it's working fine!)
Before I covered the corners I did get some old blown in insulation for free as well. This stuff I put inside old plastic grocery bags and then stuffed in the corners and the sides. This doesn't help with heating the tub up, but after using the tub one day, the water remains at 90 degrees F the next day so it cuts down on re-heating time!
Fourth, I insulated the water hoses and also put in some head rests using “pool noodles” that they sell at the dollar store. My favorite store has these with a hole in the center and I would be able to add them by cutting up one side and slipping them over the hose or the edge of the tub.
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