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In this instructable I will describe how I built a hot tub for less than $100 NZ ($75ish USD) from an old bulk liquids tank, a gas bottle and some stainless tube and junk that I had laying around.
This tub is cheap and relatively easy to build and is also useful as a plunge pool in hot weather too. Oh and you can cook on the top of it too!
This tub is cheap and relatively easy to build and is also useful as a plunge pool in hot weather too. Oh and you can cook on the top of it too!
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Signing UpStep 1Stuff you will need
Parts:
- 3 metres of 25mm (1in) stainless tube
- 1 old LPG gas bottle (the kind used for barbecue grills)
- 1 bulk liquids storage tank (the 1000litre kind with a steel palletised cage)
- enough old corrugated iron to cover the outside of the tank
- scrap polystyrene packaging
- 1 closed cell foam camping mattress
- a roll of soft narrow gauge binding wire (or equivalent - you could use cable ties at a pinch)
- scrap metal parts for the legs and decoration
- a canoe paddle or something similar
Tools:
- arc welder (and the safety gear to go with it)
- angle grinder with metal cutting and grinding discs
- pipe bender large enough to bend 1 inch stainless tube
- tin snips
- heat gun / paint stripper
- box cutter
- strong pliers with a sharp cutting edge
- the trusty knockometer
- various clamps
- magnetic welding clamps are handy
- hacksaw (omit if you're deft with the angle grinder)
- handsaw/drawsaw or equivalent
- narrow nail punch/set or a strong nail
- cordless drill with a 2 - 3mm bit
- a vivid or permanent marker pen
- a gas axe is an optional extra here if you have one and aren't afraid to use it
- 3 metres of 25mm (1in) stainless tube
- 1 old LPG gas bottle (the kind used for barbecue grills)
- 1 bulk liquids storage tank (the 1000litre kind with a steel palletised cage)
- enough old corrugated iron to cover the outside of the tank
- scrap polystyrene packaging
- 1 closed cell foam camping mattress
- a roll of soft narrow gauge binding wire (or equivalent - you could use cable ties at a pinch)
- scrap metal parts for the legs and decoration
- a canoe paddle or something similar
Tools:
- arc welder (and the safety gear to go with it)
- angle grinder with metal cutting and grinding discs
- pipe bender large enough to bend 1 inch stainless tube
- tin snips
- heat gun / paint stripper
- box cutter
- strong pliers with a sharp cutting edge
- the trusty knockometer
- various clamps
- magnetic welding clamps are handy
- hacksaw (omit if you're deft with the angle grinder)
- handsaw/drawsaw or equivalent
- narrow nail punch/set or a strong nail
- cordless drill with a 2 - 3mm bit
- a vivid or permanent marker pen
- a gas axe is an optional extra here if you have one and aren't afraid to use it
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Aside from this utopian vision, I'm pretty clueless about carrying the project out, as revealed in the following questions for those of you who are handier than me:
1- Someone mentioned concerns about superheating the water if you use a rocket stove, because they burn so hot. Should I be worried about that possibility with the stove I am using? (see picture).
2 - I haven't acquired the bathtub yet, and am trying to decide between fiberglass (I can get an awesomely gaudy giant pink one at a used building supply place for $70) or cast-iron (smallish used ones starting at $200). Aside from price, I think the fiberglass option would have the advantages of being easier to move, easier to cut the outlet hole, and easier to find one that is sufficiently deep. The downside would be that fiberglass is more fragile. Thoughts on how I might mitigate the fragility of fiberglass? Are there other pros and cons I should consider for fiberglass vs. cast iron? Other tub materials I should consider?
3 - If I run the tubing partially through the chimney (assuming I can get the tub high enough for the water to flow properly), will that help capture some of the heat that would otherwise be lost? Is there any reason I shouldn't do that (e.g. the risk of superheating)?
4 - Some non-metal tubing is rated for quite high temperatures. Am I right in thinking that, nonetheless, it would be unwise to use PEX or other non-metal tubing in place of any part of the metal tubing because it could melt? I hope I'm wrong, because PEX is so much easier to work with, I have bunches of it lying around, and would be much easier to configure with respect to connecting to the tub because it is somewhat flexible.
5 - Aside from having additional steel plating welded onto the rather flimsy bottom of the stove, what can I do to prevent it burning out? Would putting a layer of fire brick in the bottom help? Other material?
Thanks in advance for any advice!
I hear alot about not using copper pipe in chloronated water and rather to use 316 stainless steel, it's just the price difference between copper and that grade steel is vast...
so is there anyone that tried copper in chloronated water?
And is their any other alternative tubing to copper and steel.
Another design i was thinking about was maybe using a barrol, fill the barrel with water, heat the barrol to get water to near boiling, have coiled polypipe in the barrol where the pool water will run through, what you guys think?
It's like a nerd trying to find a wife, in the end you have to settle.
I used your basic idea but modified the water heater :D takes approximately 2 hours to heat the entire thing! :D I am also using a pump as the pipes in a radiator are too small to sustain natural circulation in an effective way :D
but how do you keep it clean ? cause the water turns bad really fast !
A "fouth" leg makes it wobble, and it's a pain trying to level a 4 legged stool, table etc.
Stunning projetc Veloboy, well played sir
Just a word of caution to those who don't know about these things. Common sense would tell you that if you emptied the LPG bottle and even triple washed it with detergent and hot water that there couldn't be any gas left in it.
THIS IS NOT SO! With both gasoline tanks and LPG tanks, the steel can and does become impregnated with the fuel and can leach out for MONTHS after it has been emptied and even triple washed with detergent and hot water!
I have two personal friends that fortunately lived through the experience, though not without scars to prove it. In both cases it had been less than ten to fifteen minutes since the last wash and the time they began cutting/ welding. They both woke up in the hospital!
If you must use an LPG tank, it is best if you can do it with the tank FULL of water with an Oxy/Acetylene torch AFTER triple washing. It is dangerous to cut with an electric grinder when it is full of water for what should be obvious reasons.
It can be done safely, but if you don't KNOW what you are doing, it is better to either find a different container (a 10, 15, 30, or 55 gallon drum would work very nicely or an old hot water tank) for your heater or take it to a professional to have them cut it open for you, IF you can find one that is willing to take the risk.
Please feel free to copy and paste the above warning to the beginning of step 8. It could save someone's life. I know of others that were not so fortunate.
Again, Very nice! Awesome artwork!
Thanks for sharing it!
If you fill them with sand though, they cannot get enough oxygen to explode, without the risk of electrocution.
The project looks very interesting and much cheaper than other options on the market.
I would think 1½" - 2" pipes would be better for natural circulation of the hot water. You risk the heater actually boiling, if the circulation is too slow.'
For the heat however I rigged up a
- 500gph bilge pump from a john-boat in our pasture to supply the water to the piping and heaters cores.
- 2 heater cores from a local junkyard ($15)
- 8 feet of flexible copper pipe ($10ish)
- and a large wood burner/heater
The process was that I drilled to holes in the back of the wood burner for the copper pipe to be placed directly in the flames, from there the water was ran up the smoke stack where I had placed the heater cores in-line with the exhaust fumes/air from the fire. (At first I thought that might melt the fins on the heater core but after 2 summers of use no issues)
I had a photo of it posted on collegehumor.com (a friend thought I was truly redneck...) but since have lost it.
Great idea however using the pre-made metal basket. We had to wrap several layers of insulation around the trough to keep the heat in after the fire went out. Otherwise it was spitting boiling water into the tub while the smoke usually rose above us.