I just replaced my Sta-Rite heater with an electric heat pump. I had the Sta-rite for 3 years when the heat exchanger started leaking. Support claimed it is caused by my water, but you really can't refute them, and it is out of warranty. Repair would have been close to the cost of buying a new one and with the price of propane at 2.75 a gallon, I went with the heat pump. Plus the heat pump has a lifetime warranty on the heat exchanger and 10 years on the compressor. Down side is it doesn't heat the water as fast, but does keep it at a steady temp once it is warmed.

Good Luck with yours - I have parts if you are interested