Do-It-Yourself Solar Swimming Pool Heater

by daveryder

687K23654

Intro: Do-It-Yourself Solar Swimming Pool Heater

I made this solar-powered swimming pool heater out of common materials anyone could get, with ordinary tools most average homeowners have (or can borrow from friends). A friend of mine named Ace gave me a sliding glass door that was going to be thrown out from a job site he was working on (he's a roofer, and the door had some minor cosmetic damages to the metal frame).

STEP 1: Building the Collector Box

I decided to make it out of pressure treated 2�4s and 3/43 plywood - the glass had leaned against my studio for over a year and you can see weeds and the weather had them filthy (wow I need to pressure wash my siding):

STEP 2: Sizing the Box

So the size of the collector box was dictated by the glass size (76″ x 46″). Here’s my little helper buddy Muggy (my 6 year old son) helping me lay out the copper fittings - he was a big help throughout the entire project :) . Also you can see part of my German Shepherd Hoppy - she was NOT a big help:

STEP 3: Copper Flashing Backing Plate

I ordered a 102 x 203 roll of heavy copper flashing .0216 (standard heavy weight for larger craft work, roofing and range hoods etc.) from Storm Copper Components - they are great, lowest price I could find and when I unrolled it it was almost 63 longer than 102 :

STEP 4: Manifold and Backing Plate

I cut it in half and laid the two sheets under the copper manifold I made from 1/23 copper tubing I got from Lowes (the total copper cost in this project was around $250.00):

STEP 5: Soldering the Manifold to the Backing Plate

Then I had a hard time soldering the tubing to the flashing, the heat tended to make the flashing buckle - I screwed the tubing down tight to the flashing with metal strapping, and just did as much as I could - skipping spots when the gap got over 1/8 of an inch or so. Still I made contact with around 70% of the tubing I think:

STEP 6: Building the Support Structure

I used my deck for part of the support, and sunk 2 4×4 posts for the other side. There is solid bedrock about 8 inches down there, so I dug big holes, used a rock hammer-drill to drill holes into the limestone at angles and put 1/2″ rebar in the bottom, which I then filled with 4 - 80lb. bags of premix concrete (we get some serious thunderstorms with strong winds):

STEP 7: Calculating the Angle and Running the Supply Pipe

I mounted it at a 45° angle, which may seem strange (my latitude is 38.42444) but here’s my reasoning: According to this cool sun angle calculator, that is approximately the optimum angle for me during early April and late September between 10:00AM and 11:00AM, which is when I need the heating most - during the middle of summer the water sometimes gets too warm, so maybe I’ll be able to run the system at night and radiate some excess heat.

For the supply side, I tied into the pipe going from the filter to the jet, and used 3/4″ PVC which I buried in a shallow trench (There is a tee with a drain plug at the lowest point, for winterizing):

STEP 8: Hooking the Supply Pipe Up to the Pool Pump

I thought I might need a valve between the jet and the output to the heater, but it wasn’t needed - there is a lot of pressure going to the solar heater:

STEP 9: Mounting the Box

I painted the interior flat black, and used weather stripping between the wood strips supporting the glass and the glass instead of silicone - it’s not airtight (there are several “weepholes” drilled in the bottom for condensation). This way if I ever need to I can unscrew the trim and remove the glass easily:

STEP 10: Intake Valve

I can turn it on or off with a simple valve:

STEP 11: The Outflow Pipe

The outflow is copper tubing:

STEP 12: Install the Glass and Trim

Here’s the finished heater with glass installed and trim (I’m going to treat the trim and support boards with the same color stain/water seal as the decking and the collector box when the weather forecast calls for a few days of sunny warm weather).

Here is a little data I’ve been able to collect:
It is flowing at 3 gallons per minute (180 gph), and at 10:30AM on a sunny day the pool temp is 58° (it was 54° this morning at 8:00AM). I filled a gallon jug with water from the outflow of the solar collector (20 seconds) and the temp was nearly 61° - so it looks like on a really hot sunny day I could hope for a 4° or 5° rise in outflow temp. I think the pool is around 10,000 gallons, but trying to figure the math of it makes my brain hurt (I’m a musician, not a mathematician dammit!) and I guess it really doesn’t matter - if it works and I get even a few more days of comfortable swimming per year, then I’ll chalk this up in the WIN column :)

BTW if you get a chance how about digging this? Digg this

54 Comments

zacker 3 years ago

This is probably one of the best DIY pool heater designs I have seen... not only does it seem to work great but it actually looks great as well... one question though, would it work a bit better if your output back to the pool was under water? It seem I recall reading that someone who made a heater said when they made their output flow directly into the water, it made a noticeable difference because the water flowing from the pipe and falling into the pool was actually being cooled some by the air. Oh well, at any rate, great job on the build and thanks for posting it...now to find a couple old gals doors... lol

daveryder 8 years ago

UPDATE 8-2-2015: Ok I have a confession to make here guys: I took my heater down 2 years ago, for a number of reasons I'll enumerate. 1. Every spring, no matter how thoroughly I drained and forced air through the pipes with my air compressor, somehow water would get inside the pipes and freeze, and every spring I would have to take it all apart and solder in couplers or hammer small splits back together and solder them all shut again - BIG TIME HASSLE. 2. Extra time swimming in the spring was really not that much, because you kind of want it to be good and hot outside when you want to swim, so even if the pool water was warm, when you got back out especially if it was windy, you were freezing. 3. Extra time swimming in pool in fall stopped making sense due to same issues in spring PLUS the fact that your maintenance goes WAY up from all the falling leaves etc.

I'm actually with leebarrett (way above comments 5 yrs ago) in that in mid summer it gets way too hot! I deal with that with a fountain I run at night that cools it off (a little bit) at night. So, bottom line, it was a fun project and good experiment, but unless someone smarter than me can figure out a way to keep the copper tubes from freezing, I honestly can't recommend this instructable anymore. Also, plastic tubing is not a viable alternative, I have a special needs child who drinks small amounts of the water even though I tell him not to, and I think his friends do, too - which is why I use the smallest amount of plain chlorine bleach as possible to kill off organisms, and knock down my PH with tiny amounts of muriatic acid and do it at night so everything gets distributed before kids swim in the morning. The hot sun would leech PCB's (or BPAs or whatever the hell heated plastic leeches) into the water from black tubing IMO - a risk I'm not willing to take.

I'm truly sorry if I wasted anybody's time/money with this instructable :(

Sincerely, Dave

TonyC247 6 years ago

Hi Dave. Unless you rotate your frame 90 degrees when draining it, the parallel configuration you've created will be almost impossible to drain completely, even with an air compressor. My guess is that the damage you experienced was restricted to the tubes below the input and output pipes? You would either need to add a drain plug on the bottom (at the lowest point), or reconfigure it into a serial flow system to prevent that. With a serial system and the cold inlet at the bottom with a backflow preventer, you could disconnect the system from the pool pump and rely on the thermosiphon (convection) to circulate the water. That would mean it would only move water through the system when the water in the collector was being heated and it would require no moving parts. If the flow rate wasn't high enough you could obviously add a pump to move the water.

SisoA 8 years ago

Hello Dave,

You could use a Polyethylene hose. It doesn't leech BPAs (neither PCBs). It's a safe plastic and quite cheap. Was researching for a similar project when I found yours.

Cheers for your experience and best regards to you and your child.

andrefierens 7 years ago

Hi Dave, some windscreens might help, feeling warm, when you get out of your Pool. You also might enjoying sunbafhing !

Thank you ! I love your instructable .

JoshH20 8 years ago

You could try making it a closed system so that only the heat is transferred via a pipe inside the pool. Then you could add an anti-freezing agent of some kind to the system. It would need to be something that only prevented freezing though. As far as the too hot in the summer issue you could add a shut off valve that would let you restrict the flow to the pool when the heat wasn't needed. I'm just spitballing this so I haven't done any specific research into it. Just top of my head ideas.

cm3stars 14 years ago

Nice work! I was wondering if a modified version might have the water intake at the top of the panel, say upper left. And the outflow at the lower right. That way if you had (10) six foot pipes in your manifold the water would have a 60 foot run in the pipe instead of 10 pipes each only running six feet. I think your outflow temp would be substantially higher.

GOOD OL BAD GUY 11 years ago

The object is to cool the collector, the longer the water is in the pipe the hotter the water AND the collector will be hotter, i.e., not cooled as well.

Like any heat exchanger the greater the temperature differential the greater the efficiency.

AwlDuhrage 8 years ago

The rate at which heat is transferred is governed by three basic factors: 1) the type of materials involved (in this case, copper, black paint, solder, and water, all constants regardless of the length of pipe), 2) the surface area involved (the length of the pipe seems to be a factor, however, since the water is flowing, the diameter is more important), and 3) the difference in temperature. The temperature delta is the factor pointed out by Good Ol Bad Guy. In the collector, as the water flows from inlet to outlet, it increases in temperature and its ability to absorb heat is reduced. This can be mitigated by pumping more water.

AwlDuhrage 8 years ago

I would have used a standard diverter valve (used with in-ground systems).

AwlDuhrage 8 years ago

I'm a bit late to the party, by six years, a couple of comments, though. First, plastic will absorb heat from the sun and is a viable option for use in solar heating panels. Plastic is not as efficient as metal, and has heat and pressure issues that need to be mitigated depending on the environment.

Second, thermal convection will not help the flow of water through this system. The water be pumped through the tube will prevent any convection currents from being formed. Also, the tubes are too narrow for such a current. If anything, capillary action might contribute a small amount of force, however the tubing is probably too large for that.

Another comment about using more but shorter pipes to increase surface area is not quite correct. Each pipe uses a small length for the connection, so two 10 unit long pipes will have four connections whereas one 20 unit long pipe will have only two connections. If a connection uses say 1/4 inch of pipe, 1/2 inch more is lost when "1/2 length" pipes are used. On the other hand, short pipes, arranged vertically, will reduce the back pressure the pump has to work against (shorter head) and might have side-effect of reducing the flow at one end or the other of the panel. Either way, this will double the amount of connections, each one being a potential source of failure, and hence the work to build the system. I am curious as to what the optimum separation of tubes on the flashing is - too far apart and heat is left on the flashing, too close and the heat is distributed across more water - requiring more water (= more pumping = more power used, also means more pipe was used than necessary = higher cost with no gain) to get the same amount of heat from the water.

There is nothing wrong with the flashing buckling while being soldered, provided that it remains reasonably flat as in not curving so that the surface is not struck by the Sun. The important factor is that the flashing be connected to the tubing to maximize the heat transfer to the water. The 70% contact cited roughly translates to 70% as efficient as it could have been.

Pumping from the bottom has the benefit of using gravity to create back pressure to distribute the water evenly throughout the pipe, provided the inlet and outlet are at opposites ends (diagonally opposed corners) of their respective headers. My system will use a solar powered powered pump (eventually) and be mains-backed.

YvonL 8 years ago

Great webiste, I have been looking for a way to use my pool for the winter as well as during the summer. Having a solar powerd heater would be great for that. Do you have any sources for getting the solar panels? It is not like you can just pick them up a Wal Mart. http://poolsolarwa.com/solar-heating/

dcgall 9 years ago

I've been looking into some type of pool heating system. I live in Arizona, and once we hit June - heating is NO PROBLEM. Our problem is friends come to visit from the North during the winter months and expect to go swimming. Well, believe it or not, Arizona isn't 100 degrees every day and our pool only gets to 50 degrees during the winter months. I want to build a heating system that I can drag out a week before visitors, heat up the pool and put it away. At first I was mere minutes from building the Red Neck Pool Heater system that utilizes a copper tubing system that is heated by my propane grill. The reason I stopped was a post I read about copper turning the pool green. The last thing I wanted to do is screw up the pool chemistry.

After reading the posts here, it seems that copper is the preferred choice and barely a hint about pool chemistry. Is it because the solar water temp only gets to 80 +- degrees? Any educated words on this topic? AND, can I only expect to get the temp to 80 +- degrees? I prefer 85. Thanks, I appreciate any guidance.

fabianchess 10 years ago

I have built one of these back in 1978, instead of copper I use tar paper and black hose, starting from the center it slowly work in a circular fashion to the out side of the bull eye. I put a splitter on return water from the filter and could gage the tempure coming in to the pool and all it cost was the cost of clean pool water. I did build a box and put Plexiglas on the top to trap the heat on the black hose and tar paper.

mr fat 10 years ago

Brilliant job! I am wondering if vertical heating pipes would work better cold water in at the bottom?

vistal 11 years ago

Copper and chlorine dont mix your pool will start turning green and the copper will soon be eaten away. great Idea i build them myself with black PVC/

useraaaaa 11 years ago

who needs pool heater.
make pool cooler please.
More Comments