I'm happy to report that the pool temp is now up to 80ºF and we can swim again. Thanks for the nudge Carl & Debbie! Here are the updates to the home built solar system since I last posted about it. First of all we had proved the concept but had some issues to solve. The centrifugal pump that we used to pump the water up to the roof of the casita kept losing it's prime. So I changed the check valve on the suction line that rests at the bottom of the pool and fixed that problem. The original check was cheap and just didn't work. I also had a concern that the system would have to run all the time to have flow thru it. (read: expensive electricity usage). There were also issues with air locks in the tubing that would prevent flow on start up and require that I purge the entire system to force the air out of it. These opportunities were solved by adding a 450 ltr. water tank (approx. 120 gals.cap.) w/ a level switch to control the pump up on the roof of the casita. Now the pump would only have to run when the tank level was low, and it provided an air break in the system. This solved the purging issue. Next we doubled the capacity of the black plastic tubing by adding a second 4' x 8' sheet of plywood full of tubing. On a sunny day without clouds I get about 112 to 117ºF water out of it, with the input water at about 74-76ºF. This is a gain of approx. 38ºF which is phenomenal. The addition of the black water tank also helped with the solar gain by providing some preheating of the water prior to it's entering the black plastic tubing. But we also have had warmer weather so that has added to the mix. I also had a "Solar Pool Pill" muled in from the USA. Think of it as a liquid pool cover. It prevents pool water evaporation and heat loss via an invisible layer of non-toxic biodegradable film when the pool isn't being used, like overnight. It is shaken then pierced in 10 places and tossed into one of the skimmer baskets where is slowly releases into the pool water. It is good for about one month. See the pictures below: Pool from above. Note the two hoses going into the pool. The left one is the suction line, and the right one is the discharge with a shut off valve attached to it. This is a pix of the roof top components, the tank, and the two tubing boards: Once the water is pumped into the tank the system is gravity fed because the tank is the highest part in the system: The 450 liter tank: The first set of coils: The second set of coils: The pump: These are some pictures of the solar pool pill and the skimmer: Pill in the skimmer This pool holds 12,300 gallons so it takes some pretty hot water coming in in sufficient quantity to change it's pool water temp by 10ºF, but if accomplished it can extend the swimming season in our part of the world by a couple of months, hopefully more. My cost breakdown: 1.water tank: 708 pesos 2.new pump: 810 pesos 3.concrete blocks: 78 pesos 4.electrical supplies, including float switch: 648 pesos 5.pvc pipe fitings, clamps, zip ties: 509 pesos 6.paint: 200 pesos 7.misc.: 445 pesos 8.labor: 1400 pesos 9.wood: 416 pesos 10. Solar Pill: $16 USD Total: 5214 peso's (approx. $360 USD @ 14.5:1)+$16.00=$376.00 USD My good friend and fantastic fabricator....Karl......PRICELESS!!