Big flat metal tanks? worth a try?

If you have the "solar bug" then put up some PV panels in addition and drive some DC pumps at the same time.

Get the newer "enameled" metal roofing which will resist corrosion.

Before you do anything consult with a mechanical/electrical engineer. A good engineer can calculate the inputs and outputs of such a system. Then you can estimate the cost/benefit before expending a large amount of time and coin on such a project.

thanks! If you are referring to my current system, are you saying my flow is too low/ i was wondering that too.. Any particular DC pump/PV panel set up you'd recommend?

thanks again

Sounds expensive/complicated/heavy/leaky. They sell roll-out pool heating panels that do that for very cheap - you can get 4x10 plastic mats for under $100. And they will weigh far less when full, and will be a lot less likely to leak.

I'm w/Jflorey2 on this one. Better/cheaper/faster. See Fafco and others for examples. Or, for DIY stuff, see Builditsolar.com.

thanks, makes sense. I just bought a used 2HP pump. I am thinking of running it as a separate system, hooking up a 2 inch pipe to 4 x 500' 1/2 inch PE pipe coils in parallel and laying them on the flat roof pinned down by some used metal strips laying on top, returning to the pool in a 2 inch pipe. I guess it will use quite a bit of electricity, but my concern is more with the water temperature than with the electric bill, unfortunately I cannot run a gas line to install a gas heater. I wonder if that will be just as good as my more elaborate "box" set up..

If you are concerned about water temp. increase using solar energy, as well as efficient and perhaps cost effective methods that work, and until you learn more about fluid mechanics, pressure drop vs. fluid velocity, pump flow vs. pressure drop, why laying coils on a roof and expecting any meaningful heat transfer between the surface and the coil is folly, and a bunch of other stuff, know that what you are suggesting is mostly a waste of time and resources, but suit yourself.

One more time: Get pool water heating collectors made for the purpose. Not a plug, but see Fafco. Better/cheaper/faster. Start with a heater aea ~ 50% as great as the pool surface and work your way up.

ok thanks! i appreciate your honest, practical feedback. I get your point, but part of the fun is to rig it yourself with your kids and have fun/learn doing it!. Honestly, the Fafco systems look suspiciously a lot like what I described above... It's a flat black tar roof, it's a bunch of black pipe, it's water running through it, after all. I guess one home-made BTU is worth 4 bought at the store!

PS. we went swimming both Sat and Sunday this weekend (pool at 71 degrees)... pretty chilly at first, but my son and I take it well... so I feel confident that even if the effect is minimal, we should be Ok for the summer

Sounds like a bad idea. Most successful pool systems use high flow rates. They achieve this with either large diameter piping or (more commonly) a great many small diameter pipes connected to large manifolds. Long 500' coils sounds like a mistake (lots of resistance, low flow rates.)

Why wouldn't you go with the cheaper collectors that are designed for this? 500'x1/2" poly tubing is 30 square feet and would cost about $50. So to get the same area you'd need to spend $83 for just the piping, plus a lot of labor, plus you end up with a lower performing system. Why not spend $90 and get a collector designed for this? You'll still have plenty of work to do even with the prefab collectors.

Also for pumping I would recommend not using an AC pump. Find a high flow rate DC pump (rated for your expected head) and go solar direct with an LCB or similar booster. That way the system only runs when the sun is out.

this sounds great actually. In my current coil system, i did limit to 200ft per coil in parallel. I was just thinking "what a heck" let's see what happens, but it sounds like it would be wasteful...

thanks for the reality check to both of you. I'll keep you posted

I appreciate the fun of DIY. Did it a lot. Thought I had learned a lot and was pretty smart. Then my curiosity and desire for better/cheaper/faster and smarter pushed me back to school where I found out how abysmally ignorant and stilted most of my efforts at effective use of alternate energy had been. Not evil - just a lot of time spent driving around in mental 1st gear impressed with the high rev noise I was making and the wheel spinning I was doing - Things like thinking a piece of black pipe on a black roof is a lot like a flat plate solar device (not even close).Teach your kids, but teach them things that won/t need to be blasted out, unentrenched and unlearned so as not to be impediments to learning better ways to do things later.

Take what you want. Scrap the rest.

I'd argue that your experience doing things the wrong way makes you wiser overall, especially after you learned how to do them the right way.

One of my first solar projects was a system that 'grew' from a generator-based off grid system for an airport to an 11kw, 42kwhr solar based monster. I made a lot of mistakes along the way - but afterwards I could describe with good accuracy all the ways you should _not_ design such a system. (And the owner got over a decade of use out of it.)

Understood.

I'd suggest mistakes and doing things wrong makes one wiser only if a comparison to a better way to do something comes on the scene. Catastrophic failure is one flag that there's something wrong and can point the way to progress. Spreading irrigation tubing on a flat roof and running water through it on a sunny day will certainly heat some water. There are much better ways to accomplish the same result, but they probably won't spontaneously jump out as a blinding flash of the obvious. With no way to understand much less know what's happening, I'd suggest that a better way will not jump out. Youngsters will learn the sun will heat water and that's good. However, they will not learn that the method described is mostly an inefficient waste and so not learn much more than they would by placing a dark object in the sun.

One of my early backyard air cooled flat plate designs caught fire, but I was close to 30 when that happened, and my brain was in adulthood and able to analyze and improve. Because of that, the mistakes were not repeated. I made lots of other mistakes, and still do, but fewer as I learned more (and developed good mentors who took pity on me).

My point in the post above was if you learn the wrong young, the bad habits and incorrect thinking and assumptions that are more easily entrenched in the young mind (and so probably harder to blast loose in adulthood) are impediments in the future when they need to be unlearned/corrected and only make the adult learning process longer and tougher in retracing/correcting wrong or dead end paths.

Youth makes enough mistakes on its own. Learning incorrect in youth from those ignorant of what they are attempting to teach is a disservice to the student. Ever have a teacher who didn't know the material from a hole in the ground ?

This sort of reminds me of a short essay by Charles (nom de plum Elia) Lamb story about how a young Chinese boy discovered roast pig when he accidently burnt down a barn, everyone before that eating the pig live. After discovering the delights of roast pork vs. eating raw pig, barns were burnt down en masse to produce the new delicacy. Grills were discovered long after that.

Or, the story about a young bride who's first dinner for her husband was a roast cooked by first cutting off about an inch from one end. When asked by her groom why she did that, her response was that was how she was taught by her mother, and that her mother always did it, and the roast was always perfect. Next time they were at her parents house, the groom inquired about the roast cutoff to his mother in law and how that improved the cooking process/flavor/etc. She responded: Oh, it has nothing to do with cooking. It's just that when your father-in-law and I were first married, we could only afford a few pots & pans and we only had money for a pot smaller than most roasts, so I cut about an inch or off the bottom.

If you don't know what questions to ask, you won't get any good answers as to why things are as they are, or how to make them better, except by mistake, and/or maybe much later. .