Introduction: Wood Burning Pool Heater - Great for Suburban Pools
In this instructable I will go through the steps to build a simple and effective wood burning pool heater. I have used this to heat our pool especially in the spring and fall for several years and have been very happy with the results.
Step 1: Step 1.0 - the Barrel Stove - Getting Started
This project starts with a barrel stove kit. You can find the Volgezang kit I used here or the U.S. Stove kit here. The kit comes with a door, legs, and exhaust stack attachment with damper. There are also double barrel kits as well but for this project I don't think that is necessary.
You will also need a 50 gallon steel barrel which can be found at local scrap yards, recycling centers, craigslist, etc for less than $10.
Once you have these parts together you are ready to get your barrels stove built.
Below are some additional products for the barrel stove that I have found to be beneficial but not required
Step 2: Step 1.1 - Building the Stove
The kits come with pretty much everything you need and directions to go along with it so I will be brief here. You start by laying out the door centered on one end and mark the inside with a scribe or marker. Then use an angle grinder, reciprocating saw(sawzall), or jigsaw to cut out the whole. Next you will drill holes for the door screws and screw the door to the barrel. Line up the two legs on the bottom and mark holes to be drilled. Drill holes and attach legs with provided screws. Lay out exhaust pipe connector on back top of barrel and then cut, drill, and attach.
You can purchase a grate for the inside to hold the wood or just use some old barbeque grates as I did. Before painting anything make sure to burn off all the paint on the barrel with a good hot fire. Let the stove cool and use BBQ paint of your color choice to paint the stove. You are now ready to convert to a pool heater!
I have a full video walkthrough of this step here.
Step 3: Step 1.2 - Ready for Fire!
In order to create proper draft you will need to attach some sort of piping to the stove. I used standard HVAC 6" duct but you should not use this inside or be near it when you start the first fire as it burns off the zinc coating which is not good to breath. The best way to go is to look on craigslist for some old stove pipe for long term use.
You can also purchase a grate for the inside to hold the wood or just use some old barbeque grates as I did. Before painting anything make sure to burn off all the paint on the barrel with a good hot fire. Let the stove cool and use BBQ paint to paint the stove. You are now ready to convert to a pool heater!
Step 4: Step 2.0 - Installing Copper Coil Option 1
There are two different ways to go about this step and I will show you both (since I have tried both) and let you chose how you want yours to look and work.
We need to get a coil of copper tubing inside the barrel for this option. I started by drilling holes to fit a 3/8" threaded rod. As you can see in the picture I drilled the holes about 8" apart and close to the top of the barrel. I then inserted 24" threaded rod through the barrel and secured using 3/8 washers and nuts. This will make a kind of shelf for the copper coil.
During this step I also drilled two holes in the back of the barrel to accommodate the 1/2 copper tubing. You will need a type L 20' (or more if you want) 1/2" copper coil for this project. Once the threaded rods are in place you need to straighten about 12" of tubing on each of the ends pointed toward the back of the barrel. Carefully insert the coil inside the barrel and on top of the thread rods. As you push it up into place feed the open ends of the tubing through the holes you drilled in the back of the barrel so they stick out about 1"-2".
This method, in my opinion, is the better option because you get the tubing right in the hottest part of the fire. The disadvantage is that after a couple of years the coil gets build up of creosote and needs to be taken out and cleaned.
- I have a video of this build here
Step 5: Step 2.0 - Installing Copper Coil Option 2
You can also keep the copper tubing outside the barrel stove which makes installation a bit easier. You will need the same copper coil as option 1 for this method.
Role out the copper coil and slowly start to bend it around the outside diameter of the stove. If you have more than 20' of copper you can fill up just about the entire center section of the barrel this way. If you have just the 20' then I would just start at the back edge and start wrapping the tubing around the barrel little by little. I used a piece of wood and a hammer to pound the copper tight to the barrel as I wrapped.
As you can see in the picture once you get done wrapping you need to bend one open end of the copper towards the back of the barrel and use some copper 'u' clamps to hold it in place. You can paint right over this copper tubing with BBQ paint so don't worry about the bright appearance as you role it on.
This option is a bit easier and has some clear advantages and disadvantages. It is easier to install and allows you to use a longer copper tubing which could in theory improve the efficiency of the heater. You could also use multiple loops from the diverter (more on that later) and heat more water at once. Disadvantage is that you lose a lot of heat this way as the outside of the copper tubing is open to the air and it actual cools it a bit. I measured hotter temps coming from the coil inside than the coil on the outside.
Watch the video of this configuration here
Step 6: Step 2.1 - Soldering and Pump Connections
Once you have your coil installed either inside or out you are now ready to make some connections. You will need to use some copper pipe and fittings for this step. If you are not familiar with how to solder I have a video how to solder that anyone can follow along with.
It doesn't really matter which end is the incoming and the outgoing so you don't have to worry about that. You just need to use some ridged 1/2" copper tubing to get down to the ground and away from the barrel stove. I would recommend using ridge copper until you are at least 24" from the stove or underground, it is your choice how you want to run the tubing over to your pool pump.
Once you are far enough away from the stove solder on a 1/2" male threaded copper fitting which will be used to convert to cheaper pex or irrigation tubing. In my case I used irrigation tubing since I had some on hand and it is very cheap. Don't' worry about the heat necessarily since you will be cycling water through, it won't get that hot.
Connect your pex or irrigation tubing and insulate with rubber or foam tubing insulation. I also buried my lines underground from the barrel stove to the diverter.
Step 7: Step 3.0 - Diverting Water to Your Heater
Now, you just need to get the water from your pool to cycle through the heater. This can be done with a submersible pump or other pump if you want but I wanted to use the pool pump that I already had to run everyday anyway. I have a full video on this diverter here if you would like to see it in more detail.
Start with 1 1/2" PVC piping and use two Y adapters to create two shorts legs off of the main through-pipe as in the picture. You will also want to install a ball valve on the main through-pipe between the two legs. On each leg use 1 1/2" X 1 1/2" X 1/2" reducing tee's to connect a ball valve and then male threaded fittings to connect your irrigation or pex tubing.
The way the diverter works is the pool water comes in through one side and by turning the main valve in the middle off a bit you create a bit of back pressure. This forces water down one of the legs and through your heater, it then returns to the other leg and up back to the main pipe. The water then returns to the pool heated!
Step 8: Step 3.1 - How Well Does It Work
This heater can easily bring up the pool temps a few degrees per day depending on the size of your pool. I normally run mine in the spring and fall the most and use our solar heater and solar cover in the summer. I have a video that gives the temp measurements and water flows here
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