Solar Hot Water For Swimming Pool

I'm seriously doubting that you are going to see any significant increase in temperature in the pool. Even a small pool holds approximately 6000 gallons of water. The heat collection system you described holds about 1.25 gallons. With a differential temp. of ten degrees higher in the collection system you would raise the temperature of the pool about 1/600 of a degree with each cycle of the system at 100% efficiency, which is impossible. (Rough calc. CR4 guys don't go crazy on me...please.)

Your system would work great with a 60 gal. hot water tank, but for the pool I suggest a solar cover for the pool itself. I use one in Florida and it keeps the pool 10 to 15 degrees higher than ambient in the day, and higher at night. You can purchase the material at any pool supply store like Pinch a Penny, for about the same price as PVC, and certainly less that the pump. Cut it with scissors to fit the shape of your pool. Its like bubble wrap, and floats on the surface of the water. You just pull it off when you want to use the pool, and replace it when you're done.

I installed something like this on my pool. I think it would be better to use smaller pipes. We have about 60 small black tubes about 20 feet long that water from the pool gets pumped through. On a clear sunny day we can raise the temperature of the pool by 1-2 degrees. We generally are able to keep the pool around 87 degrees for the entire summer (I live on Long Island in New York).

I have hear the bubble wrap type solar covers work well too though.

Give it a try and see how it goes. You are not spending a lot of money on this, from what I read. Keep in mind you will have to keep chlorine in the system, you don't want the water in the pipes to get funky. Any heat you get is almost free, and the pool cover will save it overnight. It may take a couple of days to heat up.

There are lots of web sites that describe DIY solar heaters. Search on "DIY solar heaters" and you will find many good hits.

A popular method is to take black vinyl tubing and coil it flat into a box 2 or 3 feet square.

There are better methods if you want to do more work as well.

Efficiency of the system depends on where you live and orientation with the sun in the afternoon. In Florida I use seven rectangular panels that are about 3 foot by 10 foot and it makes a significant difference in pool temperature. As you go further north in latitude the amount of heat you can effectively harvest drops, particularly in the off-season portions of the year.

Freezing is another issue you must prepare for by draining the system in advance.

Geometry dictates that a larger number of smaller pipes (same volume) compared to fewer large diameter pipes have more surface area exposed to the sun. heat transfer is a function of surface area. Therefore it behooves you to use the smallest crosssection pipe as practical.

My grandfather heated our pool in WVa by running a pipe up to the top of his roof. It was a black slate roof and then allowing the water to just run down the roof tiles and collected it in the gutters which were used to fill the pool anyway. At times he had to shut off the pump to let the pool cool down. The pump was on a timer that only pumped the water during the warmer times of the day when the sun was shining on the roof. ( We lived in a valley) The added benefit was that the attic was cooler. This was an open system that would allow some of the water to evaporate. Closing the system by having the water in small black tubes would make it more efficient

A friend of mine did basically the same thing some 35 years ago), but it was the garage that had a corrugated steel roof that he used.

He had already insulated it underneath to reduce the heat in the summer in the garage (that gave him the idea for the pool heating!), so he painted it black and pumped the pool water up and distributed it in the channels of the steel.

He put in a leaf filter (standard rain water guttering filter) and made a unit to allow the water from the roof to be directed to either the pool or the drains (for rainy days)....

I do not remember how he pumped the water up, but he had quite a good flow (and a double garage roof!) Within a few sunny days he had warm water.....

It certainly made bathing even before easter (southern UK) in most years very nice indeed....Evenings it actually "steamed", it looked like it was almost boiling!!!.......

They do make black plastic solar collectors for pool water. Have you checked out the price of those? I'd think they were fairly cheap. Otherwise, I'd coil a long black garden hose on the ground in the sun and see how that works..................

Google solar pool water heating, or swimming pool solar collectors, etc.

GA Marcot! I just wish I had a pool so I could do that with mine!

God forbid a grounding problem ever develops with the AC unit.

I'd make sure that the heat exchanger had a secondary ground rod just to make sure!

Adding a supplementary ground on the heat exchanger is a good suggestion. I will do that even if my AC unit is already grounded. One could also use a GFI breaker on the AC. I think that it is what the commercial pool heaters units do.

I am always sadden when I see my neighbors use an AC unit for the house and buy an independant (expensive) pool heater. All this wasted energy. They pay to cool down the house and they pay again to heat up the pool.

I had my brother in law use his heat pump pool heater to send cold air to his house. He lives in a colder area where air conditioning for the house is only desirable a week or two in the year so nobody bothers installing one. But many people want a heated pool. He bring a flexible duct from the heat pump pool heater to his bedroom window at night and sleep well at almost no cost.

If you already have both heat pump pool heater and house air conditioner, you might want to have them blow their waste air to each others. This way the house AC will warm the air used by the pool heater and the pool heater will cool down the air for the air conditioner. This will make them both more efficient. Of course, one must insure proper air flow to avoid overloads when only one of the units is running. You cannot use sealed ducts unless they have the same capacity and are forced to run simultaneously.

As mentioned by a clever replier, chlorine can be a problem for copper heat exchanger. I used one that had nickle plated water touching surface. The cost of the heat exchanger was about $560 instead of ~$500 for the plain copper one. It is still good after 5-6 years.

Our pool used to be a little bit too cool even is summer. I got good results with a solar cover but I used a plastic film made for greenhouses (very cheap, low density PE, 3 layers, UV resistant). It floats nicely and is less visible than the bubble plastic type. Chlorine hypochloride consumption is reduced. And it makes a gentle noise with light rain, something like ice-snow on large leaves... On the other hand, you have to take it out when raising your pH.

Pool bottom is white, and a lot of radiant energy is in the visible spectrum (with some windows in the IR region), so I lay black fabric on it (100% polyester - yes, it sinks!) and the warming effect is improved.

brgds

Snel

Combine black polyethylene sheet with one of these, and you'll have a nice safety system too.

Hi Rorschach,

you're right, a safety net or equivalent device is a must.

but black PE is not the best choice, it will heat the top layer only. this will cool down quickly. my best results were with a transparent PE cover on the water with a black bottom (polyester is denser than water). heat from the bottom will dilute in the bulk of water, warming it slowly and with the least possible loss.

Snel

Using the surplus insulation layer at the bottom can also reduce the heat losses to the ground that is usually cooler than your desired pool temperature. When I installed my pool, I added under the pool 3 layers of thick poly film and one layer of foam used under floating floor. Unfortunately, I cannot really evaluate if it made a difference. It didn't cause any problem after 5 seasons, so it probably helped. It made the bottom of the pool softer than on compact sand.

If the pool is fiberglass, then eventually that flexibility will cause the fiberglass to crack and fail, just like fiberglass tubs do when they are not bedded properly.

Hi Johnny,

The biggest pitfall I see is that ABS is generally not suitable for outdoor applications because of its poor UV resistance. Go with CPVC painted black or I guess you could try several coats of black paint on the ABS, to see if it survives.

Rayzer

There are several things you need to consider;

1) Surface area, surface area, surface area. The more area exposed to the sun the more effective your unit will work. (The hotter the water.)

2) Believe it or not that ABS pipes has a little bit of an insulating factor. The less insulation between the sun and your water the better. (Go Copper.)

3) Size matters. (I'm not referring to down there.) The inside of your pipe has surface area also. It also contains a certain amount of volume. The greater amount(percentage) of that volume in contact with the wall the better the transfer of heat ergo smaller is better for the absorption tubes.

4) Flow; You mentioned using a sump pump. There is nothing wrong with this as long as it will pump to sufficient head pressure to raise the water in to your pipe. You need to do a little research on this. Also you need to consider the flow through your pipes. The idea here is velocity. The greater the velocity the less time the water is in contact with the pipe and the cooler the water coming out. This DOES NOT mean less heat transfer. The heat is actually absorbed better as transfer is more efficient. Since your trying to heat a pool and not domestic water this will work better for you. Also velocity creates turbulence within the tubes which also aids in transfer.

5) Paint it black. Both copper and aluminum are easily painted if you us a self etching primer or if on a budget spray it with oven cleaner and rinse it off after a few seconds.

6) Enclose it. After all of you hard work and investment You will want to ensure that you are getting the most out of it. Wind alone can rob you of a tremendous amount of your heat potential. And place a shiny surface beneath and surrounding it not a black one. Colors absorb light waves and change them into heat. While your tubes may absorb some of that heat you'd be much better off reflecting unabsorbed light back at it. This will also cut down on the inside temp of your enclosure and opening up avenues for more traditional building materials while reducing cost.

7) Add a solar pool cover. As mentioned in a previous post. These are definitely a worth while investment.. Not only will it aid in warming your pool it traps some of that heat in (insulate) during the night when the most of your temp is lost.

To accomplish many of these items myself on a budget in the past I visited my local recyclers and placed advertisements looking for reusable base board heaters for forced hot water. The most logical choice as they are designed for heat transfer. I packaged them 3' long each with a one inch gap from fin to fin and soldered them to log style manifolds to achieve a total length of about 6 1/2 feet. This fit nicely into a box with an overall dimension of 4' by 8' by 1' tall made out of 1/2" plywood and a few other scraps. Glazing them I used full sheets of Plexiglas and trimmed it to fit. The reflective surface was simply aluminum foil and the boxes where insulated with polystyrene. I also installed drainage valves for winter (you can blow them out like a sprinkler system also.) and a couple of check valves.

Happy swimming.

Cuprum or copper pipes have a problem with the chlorine in the water if your pool gets chlorine treated.

Expect no long life if used continuously.

We had solar systems with copper pipes perforated in less than 3 years.

Very good point, sir. Even a small amount of chlorine, sometimes as small as used in municipal water plants to purify drinking water, can cause leaks in house copper pipes after years of exposure. This is a big problem in my area (greater DC); many folks including me are experiencing pinhole leaks in their copper pipes. I believe you that the much higher chlorine concentration in a pool would devastate copper pipes in short order. These days, copper is not cheap either.

To address our pool friend's question, I would recommend the cheapest plastic pipe you can find that stands up to the sun's rays. Rayzer