Rocket Stove Heater / Furnace Above Ground Pool

If you have the time scan get all the materials you need basically for free, yea you can make it work.

It is also not without risk of causing damage to your pool if the return water gets too hot.

Getting enough heat out of something like that to make a meaningful dent in your pool temp will take a lot of effort and you will spend most of your time feeding wood into the stove. Even a large 400kBTU off the shelf gas heater will take most of the day to raise your pool temp 5 degrees. That means burning a lot of wood in a short amount of time to get performance like that.

I would strongly consider solar panels if you plan on spending any money on this kind of project.

The cheapest and easiest thing to do first is to use a solar bubble cover to reduce heat loss overnight. A thin, cheap 8 mil solar cover will slow down a lot of heat lost to evaporation.

Heating with wood is great, we've got 2 wood stoves. And wood makes a lot of BTUs. How to get those BTUs into the water needs an efficient heat exchanger.

Gas heaters range from 125k BTU to 400K BTU per hour.
Heat pumps range from 50k BTU to 125k BTU per hour.
One 12x4 solar panel will produce about 45k BTU per sunny day
A cord (@3800lbs) of dry hard wood will produce about 26 million BTU, 7k BTU per lb of wood burned. But, what is the efficiency of the heat exchanger? How many of those BTU go into the water vs up the chimney and into the air?

Heating a pool is all about putting as many BTUs into the water as you can as efficiently as possible and then keeping the heat in with a solar cover.

1 BTU will raise 1 lb of water by 1 degree.

Find yourself a old wood stove, a couple of lengths of non insulated stove pipe, and a roll of copper line. Wrap the copper line around the first section of stove pipe tight and close together. Wrap it with some rocksol insulation its 100% fire proof. Now the next part you can do 2 ways, tap into your pump plumbing to feed the coil, or use convection to pull the water out of the pool and circulate it back. If u use convection be careful the water will be extremely hot. It will also help if u insulate the out pipe with something to keep the heat in. I use this method to heat a 3 car garage in -20 weather and keeps it toasty all winter just by using a little honda civic rad in the garage and a fan. Put a electric thermometer in the garage to shut down the flow and keep the temp constant or it would cook me out. Put wood in the stove 2x per day and stove was 30 feet away from garage and water line just laying on the gorund

Yep that works great for a garage but the amount of heat it takes to warm up the air in the garage is a small fraction of what it takes to change the temperature of nearly 20k gallons of water.

Wood is a great source of heat and I've heated whole houses with it and loved it.

My point was unless you have the materials on hand, or really just want a project to tinker with, fabrication of a wood boiler to heat a pool isn't cost effective. When compared to an off the shelf heating option. You could have an 8x20 solar panel set up with a ground mount rack for around 1200 and that includes a solar controller if you do all the work yourelf. A solar panel system like that would make a big difference in your pool temps.

I made my own maple syrup evaporator last year and was able to get around 15-20 gallons an hour of water to evaporate when I had it up and running just right. It took constant adjustments and feeding of fuel to get it to perform at it's peak. This included fan forced draft air, feeding wood every 10-15 min, splitting the wood to wrist sized pieces, also balancing feed water flow to maintain consistent boil. This would be a similar experience to run a "rocket stove". Rocket stoves burn wood much the same way as a maple syrup evaporator.

I didn't have to buy any of the steel to make it but it still cost a few hundred in insulation, weld wire, and other parts.

A rocket stove will be too small, but using the method above any fire source will produce some warmed water

cfherrman said:

A rocket stove will be too small, but using the method above any fire source will produce some warmed water

Click to expand...

You just need a bigger rocket...

I thought I remembered a thread with lots of pix from a guy using a home made wood fired heater, but I didn't see it on a cursory search (put "wood stove heating" or "wood heating" in the TFP search bar)

Here is one description, you might try to private message the guy. What's your current pool temp? - Page 80

I know I have seen some you tube vids.

Just use a copper tubing coil placed in the chimney. If the water is cold coming out of the exit of the coil and the chimney is hot you need more coils. If the water is too hot then you have too many coils or too hot of a fire. Make sure your not plugging the chimney up.

Heat retention is not much of a concern, water takes a lot of heat to warm up and a pool takes even more. I would not run this thing without supervision so you just need to fire it up heat the pool and let the fire die, run a cool down through the coil and there ya go. Pretty much just the price of copper tubing

Have you priced out 1" or 1.5" copper tubing recently? Your entire budget will be spent on the tubing and fittings alone. You are going to need a single continuous length of tubing because any fittings inside the fire box are just going to leak because of the thermal stress you will be putting on them. You will also need at least a 20ft and possibly up to a 50ft coil to get enough heat transfer. I would have at least 1 foot of copper outside of the fire box before you transition back to PVC pipe. 2 feet would be better to isolate the PVC from the heat of the fire.

As Casey has explained basically you would use a drum or another good place to start is a 275 gallon home heating oil tank that at least in my area you can find for free pretty often.

You would have to research and fabricate the firebox design that you want to go with. So you will need more steel and cutting/welding tools to work with the metal. At a minimum this means a grinder, sawzall, welder, and basic clamps and hand tools.

You will need some sort of chimney material probably at least 5ft long to create enough draft for your fire.

Depending on the firebox design you may need some sort of fan forced draft under the fire.

You will want to insulate the inside of your stove to increase the heat transfer to your heat exchanger. 1" thick ceramic wool is a good choice .

At least that's how I would approach something like this to make a functional unit that could produce a significant amount of BTU input into the pool. It would also consume a large amount of wood in a short amount of time relative to your average campfire or run of the mill wood stove. With my evaporator I could got thru about half a pickup truck bed full of seasoned split fire wood in an 8-10 hour day and end up with nothing more than coffee cans worth of powdery ash. My truck is a 1500 series with an 8ft bed it holds roughly half a cord of wood when full.

Also as Casey has mentioned you will need to be vigilant about maintaining water flow thru the coil before you light the fire and all the way until the stove has cooled down. There is real risk of both a steam and scalding water hazard from a heater like this. This would not be a set it and forget it type of device.

your best bet would be to watch for a old wood stove/furnace that was set up from the factory for a water coil. usually they are air tight units and loading it twice a day and throttling it back will generate more than enough heat. On another setup we did we ran about 10ft of coil in the fire box and a 500gal storage tank then to our heater. Convection circulated the water and once again the water was extremely hot even with no pipe wrap or insulation on the storage tank. We put a pc of hardi-board infront of the coil to keep the direct fire off it. Personally i think you have a good idea and iv been thinking the same way just need to find a way to keep kids away from stove if i go that route.

Wonder if these exist in NA?

20 years ago, as a kid back in York, UK we had a central heating system (i.e. radiators fed by pumped water) that ran on both coal and electricity (or gas if available). When the coal (or wood) was burning in the fireplace the heating system could be switched from the electric/gas boiler to what was called the back boiler. I assume the back boiler was a dense series of pipes in a block heat exchanger which were situated in the adjustable flue/chimney. The chimney was partitioned into two flues and the aperture could be adjusted to set the back boiler heating level. Back then it was cheaper to run than an electric/gas central heating system, now probably more expensive, that is if coal has not been banned for home use. I guess this is similar to the rocket stove.