Those fortunate enough to own a pool know how Mother Nature can limit the number of swimming days in a season. Pool temperatures take time to hit the comfort zone on either end of the warm season but may battle triple-digit readings in mid-season. The INDEK SOLAR Pool Heater acts as an invisible solar heating system, potentially adding months to the swimming season. It's suitable for new and existing pools, and is installed within the concrete deck. The INDEK system starts working as soon as the sun comes out, cycling pool water through tubes embedded in the concrete to bring it up to temperature. A thermostat and diverter keep temperatures at the desired level, while the extraction of heat from the concrete works to cool the deck. During the hot days of summer, the system will work during cooler morning and evening hours to reverse the process, bringing the pool temperature down. Existing pools can benefit from the system via installation of the tubing in another on-site concrete application, such as a driveway, athletic court, or anywhere that the concrete surface will be exposed to sunlight. While there is no set cost per square foot, the company estimates that a system for a 400 square foot pool (which requires about 800 sq. ft. of tube-imbedded decking) would cost about $9500. The company currently installs in California and Hawaii, and plans to go national with the product this year. Summer has just been extended.