This is a design for a pool heating collector from Matthew that uses half inch plastic irrigation pipe for the absorber and 3 inch diameter PVC pipe for the manifolds.
Advantages of this design compared to the large pipe coil designs are that 1) the pressure drop through the collector is much less, and 2) the shape is rectangular and the length and width can be tailored to you space.
You might also want to check on the commercially available matt style collectors that would have about the same performance and compare the cost.
Thanks very much to Matt for sending this in.
A good design for a DIY pool heating collector is to use thin wall 1/2 pvc irrigation pipe with 3" PVC header pipe. Basically, this mimicks a commercial pool collector.
<< Matt: this is the heavier wall (schedule 40) PVC pipe -- as in the hardware stores for home plumbing drain pipe? >>
<< is this the right kind of tubing: http://www.irrigationsupplyoutlet.com/irrigation/drip-irrigation/drip-irrigation-tubing/solid-drip-tubing/a-710 is there a good source you know of?>>
<< is this this kind of fitting you use to connect the half inch to the 3 inch: http://www.irrigationsupplydepot.com/sba05012straightfunnyconnectorbagof50.aspx >>
So, the header can be as long as you like -- 20 ft long might be typical. The length of the risers can be as long as you wanted. Space the risers as close together as possible. The size of the collector can be made to match the space you have available.
Take the 3 inch header pipe. You drill pilot holes where the thin walled PVC will connect to. Next you take a tap(about $10 and found pretty much anywhere in the world)
You make threads where you previously made pilot holes. You do this for the
entire header. You now take threaded fittings and you either apply glue on
threads or use Teflon tape. You connect the threaded fitting to the large
header(manifold). You do this for both manifolds. Next you glue the 1/2" pvc
lengths to the manifold.
This will leave you a collector that is highly parallelized and VERY LITTLE pressure drop, and rectangular in nature so it uses space better. I post this here mainly for other people at this point. After everything is done use spray paint to paint the pvc. I made a roughly 12sq meter(120sqft) hot tub collector that worked surprisingly well.
A panel that is 10 ft wide would have roughly 75 risers. 75 risers at maybe 40 ft long each. Each riser would have less than .833 gpm. based on 62.5 gallons per minute total
Using same calculator I get a pressure drop of roughly .4 psi in any riser, and the header(manifold) would have very minimal as it would be a 3 inch pipe. The reason to use a 3 inch pipe is so that when you are making a threaded hole the hole lands fairly flat on the pipe. I also used schedule 80 pvc for the header to allow the threaded holes to be deeper. Schedule 80 costs a bit more money but really there is minimal amounts of that. There is tons of thin walled 1/2" pvc. But Should run similar costs to irrigation tubing. Apart from making the headers it would save alot of time and could even be a one man job.
I can verify the pressure drop as I installed pressure gauges on the system I installed. I was amazed at how little pressure was added to the system.
Back to your system. To me even 13.1 psi is high. In the pools I have been involved in we used 2" pvc which is fairly good I would have rather gone 3" but we did not use a single 90 degree fitting, and we only used tees of the jets in the pool.
We used more expensive Y fittings heated and did alot of pvc bending, and bought very large filters(about 100% oversized compared to "experts") to reduce pressure drop. And pump house was right next to the pool to limit pipe runs. Although the houses were off grid.
point being if you can split to 28 loops 500ft each and only send 1gpm per coil. You could get down to 2.8 psi drop. I would think you would save a good bit of pump energy and still have a good out come.
Someone may want to check my math.