Hydro Quip 4.0kW [15" x 2"] Flo Thru Heater [CalSpa XL] w Box (26 0011 5S K) onoffvalves Energy efficient designs contribute to reduced Energy efficient designs contribute to reduced operational costs A correctly selected replacement helps preserve the intended scheduling behavior of the system instead of forcing a less suitable substitute into an important control position Matching the correct body size and configuration helps preserve cleaner fit and more dependable service results A FloThru heater is useful because it provides direct in line heating while matching the supported plumbing and control arrangement expected by the system