Keep the filter clean and flush the system each year.

That’s really it for a gas or propane pool heater. Most failures come from restricted water flow (dirty filter, blocked skimmer) or from mineral scale building up inside the heat exchanger. Clean the filter every week during season, and once a year pull the drain plug on the heater and flush the line with a descaling solution if you have hard water.

For electric heat pumps, same deal—keep the air coils clean and don’t let leaves pile up around the unit. And if you live somewhere that freezes, winterize properly: drain the pump, blow out the lines, and pull the heater’s drain plug so standing water doesn’t crack the heat exchanger.

Ignore the sales pitch for expensive chemical treatments or annual professional service calls. Unless you’ve got a complicated commercial setup, you can handle it with a garden hose and a weekend.

Your heater will last twice as long with those two habits.