Winter Haven is built around water. With the Chain of Lakes running through town and a backyard pool behind a huge share of the homes here, the swimming season is supposed to run most of the year. Then a January cold snap arrives, the heat pump starts tripping the breaker or the gas heater refuses to ignite, and the pool that cost real money to build sits at 62 degrees. Pool heaters are also the piece of equipment most local companies handle worst: pool service routes are built around chemicals and pumps, and most HVAC companies never touch them at all. That is what this list sorts out. We looked at companies serving Winter Haven and Polk County that actually document pool heater work on their own website, and we favored the ones with a loc…