A Toasty Warm Pool Without The Propane Bills

So, you’ve got the deck, you’ve got the pool and the lounger, you’ve got the summer, and you’ve got the piña colada. All set, you might say.

Sounds idilyic, but sadly we aren’t all lucky enough to live in a tropical climate. So while sipping the cocktail on the lounger you’d be warm enough the chances are that taking a dip would leave you feeling as though you’d just jumped into the Arctic Ocean. Not a problem, just turn on the pool heater. At this point you discover just how much it costs to heat a large body of water kept outdoors and open to the atmosphere. You become the kind of valued customer your liquid propane dealer sends a Christmas card to, you are reduced to living on a diet of budget ramen, and your children wear shoes with holes in them.

[ClanMan] had almost the problems outlined above, at least as far as the uncomfortable propane bills. His solution was a surprisingly simple one, he built himself a solar water heater from inexpensive PVC pipe.

It might not be immediately apparent to the uninitiated, but the key to making an efficient solar collector from such a basic material lies in careful selection of the bores of the various sections of pipe being used. The hot water feed from the propane heater had quite a narrow bore with a fast flow rate, but because [ClanMan] needed his water to linger in the collector and pick up as much solar heat as possible, he chose a much wider bore to feed it to ensure a much slower flow. The collector itself was made from multiple parallel lengths of much narrower pipe, to preserve the slow net flow across their combined cross-section while ensuring the maximum surface area contact between hot pipe and water.

The resulting heat helped take the temperature of his pool from 75 to 80 Farenheit. This may not sound like much, but was enough to make a noticeable difference.

We’ve featured quite a few solar heat projects before here at Hackaday. Best title has to go to the Hippie-Redneck Solar-Heated Kiddo Swimmin’ Pool And Hot Tub, but we’ve also featured a very tidy coiled solar collector. All this swimming is hungry work though, so how about a solar cooker made from a satellite dish?

92 thoughts on “A Toasty Warm Pool Without The Propane Bills

  1. That statement about flow-rate is complete and utter BS, and there’s even more wrongness in his comments on the instructable. The pipe will absorb photons according to the local flux and its colour, and it will also emit photons according to its colour and temperature; the hotter it is, the more it re-radiates and the more heat it loses to conduction to the atmosphere. Running the water slower allows the pipes to get hotter and just makes it all a tiny bit *less* efficient.

    If you want to make it more efficient, enclose the pipe in a little glasshouse (simple frame with a glass lid). Or go buy a second-hand roof-mount solar HWS panel and plumb that in.

    1. +1

      The same way my watercooling blocks don’t care how long the water lingers.

      I’m not sure if I can’t use instructables because of noscript or adblock but from what I can see the build is genuinely pathetic.

      1. Likewise, some car tweakers believe that a higher GPM coolant pump provides better engine cooling! A pool cover might be more efficient: Make it black and if you have a rectangular pool, have it on a powered reel so you just can flip a switch when you want a dip.

        1. The problem with solar covers is that most of the heat stays on top. Do this enough and you get a pool that is still cold but grows a lot of algae in the top inch or so. Tapping into the water you are already pumping from the vent at the bottom of the deep end for filtering and heating that works better.

          1. True, but you could still use a pump under the cover for circulation. Besides the higher temperature, how does algae grow without sunlight? I presume the cover is blocking the light?

      2. Instructables = Evil. Making money off zero paid user content and to get all the stuff on a particular Instructable downloaded, you need to REGISTER, which equals harvesting of your personal information.

        Block scripting and TRY to download the .PDF, NOPE nothing happens. Allow scripting and TRY to download the .PDF again, you then get a “Become a Premium member today!” prompt. Click the “Become a Premium member today!” link and you are sent to a page that ONLY allows you to divulge your personal “Social Networking” personal information (e.g., Facebook, Twitter, Google+, etc.)

        Again, INSTRUCTABLES = EVIL!

    2. +1 Heat is heat. The greater the temperature difference the better. In other words, the hotter the collector and colder the circulating water the better it works. This sounds like confirmation bias. The water coming in is hotter so it MUST be getting the pool hotter quicker.

    3. Spot on, another +1 here.

      The only reason for having larger pipe is to minimise pumping losses. Other than that, you will get better total heat transfer by having the water flow faster. It’s not the discharge water temperature that is important, but the total energy over time going into the pool.

        1. Trivial notion comment: I would say m dot. Isn’t that what you say if reading it off a white board or are lecturing? That is, if you mean time derivative. Or was that an attempt to make the notation show up in the comment? (Something I knew how to do a couple years ago but has escaped my ken).

    4. +1 it is the reason why people use heatpump. They do not understand thermodynamic and the fact that the hoter the collector is, the less efficient it is. After touching the water output, they think the collector is not working and trash it or sell it.

      So, the tube design is not the best in this case. A flat design is far better and coroplast is excellent because of extra low thickness, and durability. Heat goes directly to water with low loss. We are designing a coroplast collector. The difficulty was to find a way to seal it but we solved it and find a simple way everyone can do. We are testing it and it deliver more than 500W/m2 (mesuring real time with our raspebrry pi controler)
      https://www.facebook.com/DIY-solar-pool-heater-199771200422290

    5. +1 it is the reason why people use heatpump. They do not understand thermodynamic and the fact that the hoter the collector is, the less efficient it is. After touching the water output, they think the collector is not working and trash it or sell it.

      So, the tube design is not the best in this case. A flat design is far better and coroplast is excellent because of extra low thickness, and durability. Heat goes directly to water with low loss. We are designing a coroplast collector. The difficulty was to find a way to seal it but we solved it and find a simple way everyone can do. We are testing it and it deliver more than 500W/m2 (mesuring real time with our raspebrry pi controler)

    6. I don’t think the point was to make a perfectly engineered solution. he just wanted his pool to be warmer…

      You’re not wrong, by the way. I think you just missed the point. All of you jokers that attack HaD entries might not recall the encouragement you got when you were interested in these kinds of things, before you acquired enough knowledge to understand how to do things properly.

  2. You can also put a transparent insulating blanket over the entire pool and it will accumulate a lot of heat that way. Reducing heat lost at night makes a big difference.

      1. Probably even a transparent cover would be beneficial vs. nothing.

        IIRC, a lot of pool heat loss is due to evaporative cooling. ANY cover will reduce surface evaporation significantly.

          1. Black radiates heat at night as well as it absorbs it during the day, so nope clear and with a trapped air gap is ideal. The blue of the pool bottom will absorb all of the R and IR wavelengths that hit it, which is why it looks blue. Black on top is dumb. :-)

    1. If you can keep the pool insulated from the ground, you don’t even need a blanket to keep it warm in the summer.

      Solar blankets are great at heating the top 6″ of the water, and not for much else, in my experience.

      1. Yeah I guess your location is important, the average ground temperature here is about 20 C but I live in an ideal climate zone and don’t have brutal winters so I forget what other people have to deal with. As for the covers, they must be as transparent as possible to let the light interact with the pool bottom, or you get that stratification effect and all the heat is near the top and ready to be lost again at night. It is no different from passive solar heating for a home, get the light in as far as possible and onto a dark surface with a lot of thermal mass, then use an air gap (double glazing) to trap the heat in.

  3. My grandfather made one for an above ground pool back in the early 90s. It consisted of about 100ft or so of black rubber garden hose run along the roof of my great-aunt’s house, with a small water pump. IIRC, it had it’s own switch, and would automatically come on when the pool pump/filter came on.

    Worked great! Was in the desert, so that may have helped.

  4. I guess the haters missed the part about it being a HACK.

    Did is cost less than running a real heater? Yes. Win.

    Does it actually heat the pool faster than just letting sun beam down on it? Yes. Win.

    Is it as efficient as a parabolic solar collector in an enclosed frame? No. So what?

    God if he put an Arduino on it you guys would be hanging yourselves from the nearest light pole because it’s such an overused gimmick now…

    Gotta go get some more anal bleaching kits for on here.

    1. If people offered constructive criticism that could be used by other readers to do a better version themselves then that is valuable information, well shared, and the only hatred I can see is coming from your self-righteous self.

  5. interesting read but just reaffirms that you should just buy the existing product for the job, also the final product gets the award for being commended for trying… not a lot of surface area in those pipes:

  6. This has got to be the most pathetic heater out there.

    A much better idea would to get stainless pipe (copper doesn’t do so well at pool chlorine levels) and make a thermosiphon. After the upfront cost this would actually be free to run with nothing but wood.

          1. Well I thought it was funny! We basically are taxed for being alive, a sun tax just seems like the next logical step.

            Pretty sure it was a joke.

          2. The Beatles had it right:
            If you drive a car, I’ll tax the street
            If you try to sit, I’ll tax your seat
            If you get too cold I’ll tax the heat
            If you take a walk, I’ll tax your feet

            Taxman!

          3. @sonofthunderboanerges
            Nice contraption there!

            Looks like a cheap charcoal grill with a glass lid, and don’t forget the hose.

            P.S. Don’t worry about that jonhsnow guy (misspelled on purpose), I watched that user go on like 6 different pages just to hurl insults last night.

          4. notarealemail – Thanks but it was only a thrift store purchase. I think I’m misunderstanding something about it’s operation. I don’t know if I should elevate it above the animal water container, does it need some sort of pump to keep water circulating, some sort of temperature detection, etc.I’m wondering if it will move water on it’s own when sun heats up the black pipes like a thermosiphon? It’s meant for a pool. It speaks about hooking it up to the filtration pump. But I’m using it to keep farm animal’s water from freezing in winter.Presently using a electric heater spike I bought from Agway. It was under $100 USD but the electric bill is expensive.

            Who was John’s tirade directed? Please don’t say me!

          5. > “Your comment is awaiting moderation.”
            > Ah come on why????

            Because you people are doxxing each other. This is genuinely embarrassing, both for Hackaday and for you. It seems the regulars here need lives, instead of finding fault with everything here. Well, lives or a mirror.

          6. Brian Benchoff – I know where your angst lies. However, it’s not actually me. I have been cordial to everyone and I try my best not to “doxx” anyone. Yes I am invariably the target of doxxing sometimes by disgruntled denizens. That’s just the nature of the Internet. I did find out why I was being moderated. I had tried to change my moniker 2 days ago by adding a “aka SOTB” and that tagged me as a new poster – hence moderation. I changed back to my original moniker and now it works just fine. I know you might feel that I may have stepped on your toes once but I assure you it was a unfortunate misunderstanding – do to my lack of clarity in some of my postings. I say that as you are one of my HaD heros – probably #1 out of many. I would never doxx you as I have way too much respect for your technical skills and intellectual acumen. And you can ask Sophi about something I PM’d her recently. I mentioned that I “trust” you and her with my personal data. So not empty words..Now I can’t speak for the OTHER doxxers… my HaD buddy will vouch for me on that (wink-wink)…

          7. @sonofthunderboanerges
            The tirade was petty random. Was lots of ‘anyone can do this *ramble ramble*’, nothing more directed at you.
            Search for the name into Google like so:

            OffendingUser site:hackaday.com

            Though the results are all weird because the names show up to the right as recent comments. Not worth looking trolls up IMO.
            I’ve looked up thermo-siphons but I’m not sure they would work with that device. Haven’t tried to make one either, so good luck. :) Probably will need a pump. I use on of these to turn on a small water heater or lamp.
            http://www.speedtraceheating.com/thermo-cube-tc-3-thermo-cube-thermostatically-controlled-outlet/
            Very cheap and I’ve had only one fail but that was my fault.
            I would look at buying a cheap small pond pump.
            Once again, cool purchase you found! I might buy/make one before winter hits.
            P.S. You can’t direct-message me because nobody can. Lol. No working email account.
            If/when I get a new account I’ll send a message your way. I’ll create an ‘io’ account when I’ve made something worthy of following, which could be awhile.

          8. notarealemail says:
            June 19, 2016 at 8:25 am

            @sonofthunderboanerges
            The tirade was petty random. Was lots of ‘anyone can do this *ramble ramble*’, nothing more directed at you.
            Search for the name into Google like so:

            OffendingUser site:hackaday.com

            Though the results are all weird because the names show up to the right as recent comments. Not worth looking trolls up IMO.
            I’ve looked up thermo-siphons but I’m not sure they would work with that device. Haven’t tried to make one either, so good luck. :) Probably will need a pump. I use on of these to turn on a small water heater or lamp.
            http://www.speedtraceheating.com/thermo-cube-tc-3-thermo-cube-thermostatically-controlled-outlet/
            Very cheap and I’ve had only one fail but that was my fault.
            I would look at buying a cheap small pond pump.
            Once again, cool purchase you found! I might buy/make one before winter hits.
            P.S. You can’t direct-message me because nobody can. Lol. No working email account.
            If/when I get a new account I’ll send a message your way. I’ll create an ‘io’ account when I’ve made something worthy of following, which could be awhile.

            Thanks I’ll look into that. Not quite sure why you have email trepidation, but you might consider a free www. hushmail. com account..Emails between two hushmail accounts are PGP and all headers suppressed. Not so secure between hushmail to other domains. A paid account is better of course. Also since they are Canadian they claim they ignore all NSL from u-no-hoo. Yrs you wont b able to PM here until you get an .IO account. Or you could just use this planetcalc. com/1434/#

          9. I assure you [sonofthunderboanerges] he wasn’t targeting you as an offender. :) At least I seriously doubt it.
            HaD seems to be a special case when it comes to privacy. I don’t have a working email because I’ve seen the shenanigans that go on something as simple as Wikipedia!

            Stay safe my friend, anyone could be anyone on the web!
            If I don’t reply to a message it’s because I either haven’t seen it yet, can’t think of a response, or am rolling my eyes at a bad joke lol. :)
            You’ve been great IMO. :)

          10. @notarealemail – I would like to think I am. And yes [@PurpleTurdBracket] I do reply to myself a lot. I do that because WordPress does not allow editing posts yet. I see I misspelled something, said the wrong thing, or wanted to reword something I said. I assure you notarealemail and I are two very different and unique people. Brian can attest to that as he has the server logs to prove it by IP addresses.

            Speaking of which, Wikipedia records and displays your IP address open to the public. They do that for security reasons to keep people honest about their changes to the subject material. You could use anonymizer websites (i.e. VPN) to get around that. Many political dissidents and spooks pay for it instead of using the free ones. Of course you already know that I think… :-P

            A/K/A SQTB or SOTB - Q for Quartermaster 007 Q-Branch :-D

    1. I was thinking about the same… One of those, a black pool cover and you can heat it to values you wouldnt get it there..

      Of course you have to get wood, but it is not difficult assuming you dont live in inner city , because if you do and have a pool you wouldnt have money problems, so…. For that people that lives in middle of nowhere this is a reasonable option, or you can buy one (or more) solar pannel to heat water and you wouldnt need the wood but you would pay all in the begining and get less power to heat water..

      So, getting the equipment to use sunlight is not free also, is more expensive than a thermosiphon and less power..
      Or you could use just pvc pipes but… heat water 5º in a pool can for sure make it better, but not good if it wasnt already..

      1. “Of course you have to get wood, but it is not difficult assuming you dont live in inner city…”

        You must believe that stupid “Church’s Chicken” conspiracy theory.

  7. Just add black rubber mats on the bottom of the pool. They will heat the water from bottom.
    In order to quicken the heat transfer to water, replace rubber with copper / steel / whatever painted black metal sheets you have at hand. Do not forget to add handles to pick them easier.
    Or use black mosquito net in several layers, which could be trimmed for odd shaped pools (not rectangular).

  8. I will try again to post pictures here.
    1st is my pool solar heater.
    2nd is when you dont cover up the hearter in the winter time.

    OK Help Please….I cant get pictures to be posted here.
    CAN SOMEONE PLEASE HELP…….

          1. perry – You have to give some of us more time than a few hours. Sometimes we reply weeks later. I’m just one of the “chatty” ones who has trouble stfu! :-)

            BTW I found a better image host-er called http://www.uploads.im – much less ad bloating than my beloved tinypic. Imgur is too much sharing comments. You put stuff on imgur and strangers I don’t care about votr on it and make awful comments about your work product. Tinypic just puts you too many stupid security procedures whil throwing ads at you. Uploads seems straightforward and no visible ads YET.

            A simple drawing tool is already on your Windows PC. It’s called MSPAINT.exe. You can copy images from Google Images and past them into MSPAINT. You can also capture you entire screen with the [prt sc] button near the delete button on your keyboard. You then paste into MSPAINT, Select All, move everything to top left corner, then deselect all, and grab the right corner edge of the screen by it’s white nib and crop the image down, you can re-expand the nib and all superfluous stuff is blanked out. Then you can add lines, boxes, circles, text, etc. Save it to your desktop. Upload it to uploads website. Take the generated URL and copy and paste it to HaD on a new line by itself. HaD (or WordPress) will resolve the picture for you when you hit (POST COMMENT).

            Remember only ONE hyperlinked image or link per post or you get moderated and have to wait for the HaD moderator to spring your post from WP jail… :D

  9. Pools are routinely solar heated in Australia to extend the swimming season. The setup consists of large pipes feeding a lot of small rubber (black) style pipes maybe about 1/4″ inside diameter laid on a rubber backing. About 6-8 pipes to a 6″ flat rubber bed. These are commercially available here. These runs are laid on the house roof. These have been used for perhaps 20 years.

  10. Why is this even on HAD? Will you start posting my oil changes as a hack because I modified a 50 gallon oil drum to recieve the waste oil?

    Drum roll please….
    I put wheels on a 50 gal steel drum and punched holes in the lid for catching spills. Incredible as this seems I can now put my car on my car lift and wheel the drum under the car to catch waste oil instead of using an intermediary step of using a drain pan to transfer the old to the drum. On hazardous waste drop off event days in the city I transfer the waste oil to 5 gallon pails using a hand pump and deliver it for recycling.

    1. Sounds like a lot of work. Just make a small and heavy dolly that you can sit the bucket in. Then take two pieces of PVC and make a telescoping pipe with a funnel on top. That way you just raise it to the height of the oil pan to drain and then retract it when done. Then you can move the whole unit from bucket to bucket.

  11. I’ve always thought the best way to solar heat a pool would be to put pipes in the concrete around the pool. You could heat the pool and cool the concrete at the same time. Ever try to walk across concrete barefoot on a hot sunny day?

    1. That’s a nice idea. :)
      Use dark concrete and lots of piping. Priority 1 would be preventing cracks and 2 would be preventing leaks. I’ve seen a heated garage setup and it worked very well, but one night the pipes froze and damaged one ‘zone’.
      If I were installing a pool I would consider your suggestion, though some experts would be consulted.

      1. I would think it would be very similar to a hot water heated concrete slab or tile floor, so there should be contractors with relevant experience. It would take some careful layout of the pipes, but it could probably even be self draining to help with the freezing issue.

        1. Either use a heat exchanger rather than circulate the pool water and thus antifreeze, and/or incorporate a heat pump to make the concrete even cooler during summer. Refreshingly so.
          Capital costs verses propane.

  12. Ugh, complete BS on the larger diameter pipes and linger effect. Your loosing energy and not doing yourself any favors. The pumping losses are minimized with larger pipes as pointed above, but only if you design it properly otherwise it works to increase pumping losses if you go too big. With that said, you really want as much surface area and a high pressure in any sort of heat exchanger to make it efficient, the surface area of many small pipes with as thin a wall as possible will far exceed the surface area of larger tubes.

          1. notarealemail – Hey buudy-ro’ When it’s hotter than Hades out there… you gotta’ git’ ‘er done by any means necessary… [belch]… sorry… too much Budweiser I guess… gul’ dang’ it Bobby Ray, now I gots’ to drain the dang’ ol pool!!! Next time get to the dang’ ol’ outhouse – you dang’ id’jeet! –

  13. Propane? Sounds so extremely dangerous. I regard propane as so dangerous as it would explode like a nuclear bomb the moment you look at it. Solar heating is great, but whats about using electricity as “backup” to solar heating instead of explode-when-you-look-at-it-propane? Electricity is like a million times more safer than propane, as a electricity system can be built much safer, and electricity isn’t dangerous when shut off. (propane is still dangerous when off).

    1. Propane usually has a chemical added that stinks at low concentration. And it’s relatively safe IMO. No nuclear explosion here, lol. :)

      Heating with hydrogen on the other hand wouldn’t be a good idea.

  14. 500ft of irrigation tubing coiled up on top of my hot-tub cover keeps the hot-tub at a dangerously high temperature in the summer. A small solar panel and a 24v aquarium pump circulates the water through it whenever the sun shines.

    Couldn’t be simpler

  15. @notarealemail

    notarealemail says:
    June 19, 2016 at 8:25 am

    @sonofthunderboanerges
    The tirade was petty random. Was lots of ‘anyone can do this *ramble ramble*’, nothing more directed at you.
    Search for the name into Google like so:

    OffendingUser site:hackaday.com

    Though the results are all weird because the names show up to the right as recent comments. Not worth looking trolls up IMO.
    I’ve looked up thermo-siphons but I’m not sure they would work with that device. Haven’t tried to make one either, so good luck. :) Probably will need a pump. I use on of these to turn on a small water heater or lamp.
    http://www.speedtraceheating.com/thermo-cube-tc-3-thermo-cube-thermostatically-controlled-outlet/
    Very cheap and I’ve had only one fail but that was my fault.
    I would look at buying a cheap small pond pump.
    Once again, cool purchase you found! I might buy/make one before winter hits.
    P.S. You can’t direct-message me because nobody can. Lol. No working email account.
    If/when I get a new account I’ll send a message your way. I’ll create an ‘io’ account when I’ve made something worthy of following, which could be awhile.

    Thanks I’ll look into that. Not quite sure why you have email trepidation, but you might consider a free www. hushmail. com account..Emails between two hushmail accounts are PGP and all headers suppressed. Not so secure between hushmail to other domains. A paid account is better of course. Also since they are Canadian they claim they ignore all NSL from u-no-hoo. Yrs you wont b able to PM here until you get an .IO account. Or you could just use this planetcalc. com/1434/#

    A/K/A SQTB or SOTB – The Q is for Quartermaster 007 Q-Branch

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