How to build a Rocket Stove Water Heater!!

It would’ve been way better if you just made it like this instead of that. Next time try changing that piece to this piece and it’ll be much better, trust me

The round one used less wood and didn’t use a pump. One could argue that it was most efficient.

I was a pipe welder and an insulator. Wrap that in a removable blanket. It will be way more efficient

In boilers, there is the phrase "Hot to hot, cold to cold". This refers to the optimum flow direction of water relative to combustion gasses. The coldest water should enter the stack and the hot water (or steam) should be withdrawn from a place alongside the fire. This makes sense, we can measure boiler effectiveness by exhaust gas temperature -- the cooler the exhaust, the more efficient the boiler. Obviously, cold water entering the stack will remove more heat from the gases than hot water will. The technical term is "counterflow circulation".

One thing I noticed after building several wood burning water heater is when you put the copper coil inside the stove it will get charred on the outside skin of the coil in turn insulating the water from the heat enough to be frustrating as the water can escape the heat enough to stay Luke warm! When using propane burner inside with inside coil the results were much better as it doesn't accumulate the black crust when using wood!

If you add a plain loose metal sheet into the flue, it'll help with efficiency. The metal sheet/plate heats up, and radiates the energy from the gasses in the middle of the flow onto the the coils. Might not be a ton, but I've heard that gas water heaters do that to get a few more percent efficiency. Also, if you're using a pump, you might do cross-flow on the coils. Cold water into the top and warm water out of the bottom. The thermal gradient is more efficient that way. Kind of interesting - the same principle is used in some fish gills - the unoxygenated blood is fed into the last gills first, where the water has already had some of the oxygen pulled out. The result is that the fish can "breathe" a lot more efficiently and even to lower concentrations of oxygen where they might not survive otherwise.

Nice builds!! I probably would have used a pump on both to get a fair comparison. great for a small hot tub or clawfoot bathtub with a view!

+1 for weighing the wood for the test.

Patrick just nonchalantly called us all weak 😂

I'm so glad to find this video to test which is more efficient. I knew the square one with a built-in coil inside would heat up faster. That was my first initial guess before you started the stoves. I would pass it on to my friends who want to heat up the outdoor tub. This would do it! Thanks!

From the Pacific Northwest, Can't wait to have Hot water to take a shower while camping this year. My family thanks you, without any idea how hot H2O came to camp this summer!!! lol

Some pipe wrap on the outlet (hot) hose would help retain some of that heat. Those open hoses are acting like radiators. In fact, leave enough copper to run all the way to the storage tank, and wrap that. Honestly, I'm waiting for the video where you get the water hot enough the hose melts. Great videos man, thank you!

Excellent workmanship , simplicity of design, and 100% on functionality in off-the-grid living.

"He's strong... and blows good" You got the job

I would DEFINITELY have shoved the hose from my air compressor into the pipe to clear the sand XD That sounds like fun lol. Such a cool project!

I’ve seen a number of rocket stoves come out in the last few years and my biggest thought has been application. Appreciate the idea.

I have always wondered why people put the inlet and outlet of the bucket of a thermosiphon at different levels. You could put both at the bottom or send the hot water into the bottom of the bucket. As long as the hot water coming out of the rocket stove continues upwards it will cycle. The pressure in the whole system is the same as it acts as one column of water.

Awesome build, here are some suggestions for a version 3.0: - smaller copper pipe diameter, but a way longer pipe, may help with faster heating, since smaller volume of water inside per surface area of coil touching the stove wall. Ideally the copper would be wound all the way up the chimney, to maximize surface contact and therefore heat exchange. In a theoretical perfectly efficient system, this would mean that the stove exhaust gases and the water exiting the coil would be at the same temperature. - Some kind of heat transfer substance (similar to thermal paste between computer chips and heat sinks) between the copper coil and the stove wall would be great, since the contact of the round tubing on the flat wall is basically minimized by the geometry of the round tube (only tangentially touching). Building an additional outer wall around the copper tubing and filling it up with fine sand (or maybe even filling it with lead?) should work. This will increase warm-up time for the stove itself, because it's just more mass to heat up, but should increase overall efficiency. - square copper tubing may also work, since it would increase contact surface with the stove wall.

Kudos to you sir, for working so well with that 'tricky to work', but neat looking round tubing. Bravo! 🔥🚀

Can also wrap the copper tubing around a section of pipe a hair smaller than the pipe in your finished rocket stove. The copper will then have a tighter fit around your permanent stove.