[UPDATE: See end of article about materials used and height differential! Also new pump notes!]
Just wanted to share pics and tidbits on how my roommate and I decided to heat our pool without breaking the bank. While commercial estimates were coming in at between $5000 and $6000, we managed to heat our pool with a weekend of work and about $300 at Home Depot, and about $100/year in electricity.
I should also note that I didn't come up with this method, and that two good friends, JM and DB, did something very similar before me, and we all learned a bit from various websites, including
Solar Pool Heating.
Being in southern California, our pool was about 73 degrees in the afternoons of late June. This was certainly warm enough to enjoy, but we wanted to prepare for the winter (and to see how hot we could get it this summer!). I'm happy to report that our temperature is now about 86 in the afternoon, and still rising daily.
We start with a submerged pump in the pool. Since we happened to have two free, smaller pumps, we hooked them up in series. They're driven by a 110 VAC outlet, and controlled by a simple daily lamp timer.
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| Pumps in Series (not req'd if you just get a bigger pump) |
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| Primitive Control & Measurement |
Next, the output of the pumps goes up onto the roof via some black drip irrigation tubing, 1/2" diameter, and coiled about 45 times to finish at around 6 or 7 feet in diameter.
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| 2 of the 6 coils, the other four are on the south facing side of the roof for now. |
There are a total of 6 coils, 500 feet each. The pipe comes in rolls of 1000 feet at Home Depot for $80 (we used DIG corp,
SKU # 642176), cut in half for more manageable handling.
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| 6 Coils of pipe. Roughly equal to one third of our pool top surface area. |
The construction of each coil is designed to be inexpensive. Just PVC and some zip ties. Use a wooden block to space out the PVC as you start, and use zip ties liberally to keep the coils in order. Get two spinning tables (lazy susans, office chairs, be creative!) and directly spool from the supply to the PVC. Two people work best, though it is doable with one.
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| One pretty coil. |
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| Sample coil showing PVC construction |
We decided to split the water into two channels, and have each channel run through three coils, from one to the next. We're still debating what the best speed is for the water, but this seems very reasonable. I guess we could pump faster, though it is mid-day at mid-summer, so maybe we'll want that slow speed in the winter.
The pipes are held together with simple press compression fittings. I'm astounded at how they don't leak air at all. I think they're magic.
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| Sample joint |
Then the water returns to the pool. I just measured the water coming out of the hose at 2pm to be 114 degrees F.
UPDATE: We have had an issue lately with the black tubing on the roof collapsing due to the vacuum being pulled by the water wanting to flow down both ends of the tube when the pump is off. Not sure the solution yet, maybe a more powerful pump to overcome this when it kicks on, or maybe a second pump on the roof? Maybe the black tubing is just not structural enough. Thoughts and suggestions?
UPDATE #2: Thanks for the suggestions in your comments. We upgraded to a surplus pump that is definitely oversized -- one half horsepower! The flow rate is high, but we still get excellent thermal transfer; the water comes out nice and hot despite it being fall now. We followed Dan's suggestion and bought a pump here. The pump 'inflated' the hoses just fine and we have been running for a few days without incident. Will re-update here, if we run into trouble!
13 comments:
Nice writeup Holden. Interesting facts would be the height of the roof and the ratings of the pumps (CFM, Amps) to help spec out a similar system.
(I like the photo with the bus in it!)
Good call, Jos!
The top of the roof is roughly 15 feet from the surface of the pool.
The pumps are submersed on a ledge about 1 foot below water, and are 110V, 3.5 Amps and 1.7 Amps each. We find that the second pump really helps during startup, though if the system is well primed, only the larger pump is required to sustain pumping at a good clip. (Free pump = using it still.)
Also, of note, if the system leaks at all (which ours doesn't, magically), or when the coils are emptied, the coils need to be filled by a garden hose (approximately 50 psi), as the pumps can't lift the water, they can only circulate water. Remember, the outlet hose actually generates a vacuum on the roof coils, as the water gets pulled down by gravity.
And thanks to Dad for pointing out the zip ties that are white will wither over time with the UV exposure. Went ahead and did a quick fix by coating them, and the white pipes with black spraypaint, so that the visual footprint is lowered.
Hello! I am planning on doing this to my own pool. Have you noticed a heat increase inside your house?
I haven't noticed any change in temperature. But if anything, I expect a decrease in house temperature. The solar load on the roof shingles is now getting put into the pool! Put another way, if it's 100 degrees outside, and you continuously pump colder water (80degrees) onto the roof, you'll cool your house!
That heat that is going into the pool is coming from somewhere! And its being displaced from heating something else (your house)!
Questions- What is on the end in the pool return? A check valve? What are the horsepowers of the pumps? This is very cool ( or hot I should say). What is the overall diameter of each coil? I live in Ontario and hope to augment my season and use the gas heater less. Any suggestions on an optimum size pump? Thanks
This is very cool indeed - so much so that I've tried to replicate this with my 12 foot diameter 30" deep INTEX pool. Figure I can get good heating with just one 500 foot coil and my 1800 GPH pump I purchased on Amazon. Tested it yesterday and while the water is coming out very hot (probably close to Holden's temp) it's not coming out very quickly. The pump doesn't require priming, but can I pick up the pace of the overall flow rate? Is there air in the coil? The coil sits right above the pool on top of my patio covering (pergola). Probably only 8 or 9 feet of elevation change. Any thoughts? Bigger pump? Very cool!
@jocam, regarding your questions:
1) The end on the pool return is not even a check valve, it's just a straight exit; the water will not empty out, as both ends are under water!
2) Our larger pump is 0.59 HP.
3) Overall diameter of each coil is approximately 6 feet.
4) Regarding pump, we use a garden hose to fill the tubes on the roof, because the garden hose is at high pressure (50 or 100 psi), and then we use low pressure pump to move the water around.
@ChrisC, something to try is to get an adapter and hook up your garden hose to flush out the air bubbles from your system. I'm not sure what pressure you have there, but we're on a large hill, and even at the top of the hill have over 50 psi (somewhat astounding!).
After you have the hose filling the pool (via your tube), then put the coil intake under water, unscrew the hose, and hook up your pump. I'm betting you'll see some better flow. And if you don't have any leaks, you won't experience any loss of flow rate*, as the water going into the pool, off the roof, creates a vacuum pulling water up onto the roof.
* Because we're currently investigating some collapsed tubes and lower flow rate, possibly because of this very vacuum. :-\
One option is to get a stronger pump. I use a stronger submersible pump: https://www.surpluscenter.com/sort.asp?catname=water&keyword=WPSA and I have unintentional leaks in the solar water heater on the roof. The stronger pump is able to prime effectively, so it works great.
Did you start laying the coils from the center or outer ring?
I continued to struggle with this, going down to a tiny waterfall pump (that was rated to 12 foot lift) all the way up to a high flow rate 0.75 HP pump. No luck. I did prime the coil with the garden hose - got great flow through the coil back down into the pool so there's no blockage/kinks, etc. Someone else advised me there may be too much backpressure because it's all one big coil, and suggest I split it up into parallel smaller coils. Other than trying that I am at a loss!
@Chris, thanks for your comment. I'm not completely sure what is plaguing your system, but I would concur that there's a high likelyhood that it's backpressure (major head loss). Did you find any time to re-plumb the system? You could cut the coil halfway through, for testing, and always re-join it later!
What length of pipe do you have? We have about 1500 feet and our 0.5 hp, high flow pump has no issues at all. Keep me posted, I'm curious about the challenges and solutions!
-Holden
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