I have owned this product (Sunheater/solar collector) for approximately 5 years (give or take... long enough to be uncertain what year I bought it). The conditions: I have a 4' deep 18' round above ground pool (with a perfect fitted solar blanket) and I live in the northeast. Let me start off by saying it works amazingly well. Take this spring: I opened the pool in mid-May, and pool water temperature in one day (with direct sun-light on this product) raised the pool temperature from 69 degrees f, to 79 degrees f in one day. My neighbor down the street with only the solar blanket has just reached 78 degrees f and their pool had been open for 2 weeks prior. Same weather conditions, pool size is roughly equivalent, and my pool caught up to and surpassed theirs temperature-wise. By the following day the pool was at 82 degrees. How it works: Familiar with a radiator on a car? It's like that, but the reverse process. Clean water from the pool filter with pumped into one end of this "solar collector". The water is then sent through half the tiny black (black absorbs light and thereby heat) tubes on one side, hits the end, then comes back through the other half of the tiny black tubes. The idea is, you expose more surface area to the water, than if the tubes were bigger. Since the water is cooler than the solar heat being absorbed, the heat is being transfer to the water, and then returned back to the pool. Construction: these things are built to last. My first one I owned lasted up to this season, and was damaged by a lawn mower (I'm cheap and I just lay in on the grass; I've since built a ramp for it, like in the picture). The lawnmower caught the side of it and chewed through 4 of the tubes. HOWEVER, I was able to repair it. If you look at the manual([...] it instructs you to cut off the damaged tubes on both ends (where they meet the larger pipe) and drive in #10 sheet metal screws between 1/2" and 3/4" long. Worked great! I learned this after I had already purchased another one, so now have 2 solar collectors. Maximum heat threshold: Well that depends greatly on the temperature during the day and night. I used the example of when I opened the pool and the temperature shot up 10 degrees in one day. The next day it only went up a few more degrees. There is a peak it reaches, and it is directly dependent on the temperature during the day. On consistent 75 degree days, my pool will in the mid-80's. One year when we had three 92 degree days, my pool hit 102 degrees (yes, it was disgusting, but I wanted to see how high it would go, haha). I now used my pool up until October where before it, we closed it beginning of September. I think the closing temperature was 69 degrees this year... which is not back for the late September weather we had). Issues to watch out for: There are two. 1. Definitely rig up a diverter valve to bypass the solar collector. This should be included, but it is not. Everyone has a "too hot" and "too cold" temperature they prefer.... most just don't know they have a "too hot" temperature for a pool...at least not up here in the northeast. I know I do now. More importantly, when the temperature on the pool is elevated, it requires a more vigilant eye on the pool chems. Once a week treatments are not enough with temps in 85+ degrees. I ended up with a green pool twice this summer (went away for a few days). Keeping the pool temp down helps this. 2. Use a solar cover/blanket on the pool at night. Without it, because the water is warmer than it normally would be, you'll fight a significant amount of evaporation. Adding water means diluting your pools chemical content, which means adding more chems. Problems with design: As I mentioned, there probably should be a diverter valve incorporated into this design, but there is now. The other issue I have (with the one I just bought, the older one doesn't have this problem) is with the end pieces that connect to the hoses. I use high quality pool hose, and I have to use 2 hose clamps on both to prevent it from leaking. Two hose clamps on both side (4 total) does fix the issue, but it's kind of annoying. Summary (tl;dr): I do wholeheartedly recommend it to everyone with a pool that wants it warmer, or squeeze out another month or two of usage...with the caveat that you build in a bypass to control the temperature from getting too hot (if you want), and use a solar blanket/cover to keep evaporation from being a problem (also stabilizes the temperature of the pool...evaporation = loss of heat = pool temperature going down at night).
