I have a very small pool/spa. It is roughly 7x17 and 54" deep.... approximately 3,500 gallons. We live in the Pacific Northwest. We have a Hayward heat pump that heats our pool very nicely until November and then starts working again in March. We keep the pool/spa very warm.... like 92 to 96 degrees..... We get into our pool to warm up We are starting to look at a propane heater to cover the colder months. I have a couple of questions. First, would it be safe to plumb the propane heater in line with the heat pump? If so, in what sequence? I would assume heat pump first and then propane heater because of the higher heat of the propane. The next question would be... Can anyone recommend a good, small heater for a small pool/spa like this? How reliable are they and what is the average life span? I am just starting this research and you know what they say.... "The more you know, the more you know what you don't know...."
Thanks for any help on this,