I am VERY pleased with this purchase. It's a great find. I'm disappointed to see that it's not currently available at the time of this review.I have a custom-built hot tub that needed a heater, since I wanted to move the original large heater (100k btu) to our swimming pool. I found this, inserted it in the PVC line right out of the filter, connected the 220vac, and it works great! Simple installation, GREAT price. Since it's outside, I simply mounted it inside a plastic tool box (holes at each end) to keep it dry if it rains.The heater turns off when the flow is off (you can see from the indicator light) and right back on when the flow comes back. And, of course, it turns off when it reaches the preset 'knob' temperature. So, my pump timer controls both the pump and the heater, and the tub is hot when we want it to be.It's not super fast, of course, just like every other heater of this "in-line" type used on all my previous fiberglass stand-alone hot tubs. So, it takes a few hours to get up to temperature if you let the water cool off. But we don't care, because we keep our tub hot year round. A well insulated tub with a good cover can stay hot with little noticeable impact on the electric bill.The temperature control knob doesn't show the temperature in actual degrees, so you need to use the tub a time or two and adjust the knob to your preferred temperature. But that doesn't really matter since every thermometer is different anyway, so adjustment is always necessary. Even with the fancy digital temperature readout on my big, expensive pool heater, it still required a few adjustments to get the water just right.Not sure yet about longevity. But the price is so good that if it fails a year or two down the road, replacing it will be quicker and less expensive than getting a larger unit repaired.
hunkieda 
