With revolutionary pre-mixed gas combustion technology, the MasterTemp 125 offers 82 percent thermal efficiency, the highest of any heater in its category. 1-1/2 inch plumbing is ideal for above ground pools and hot tubs up to 15,000 gallons. The MasterTemp 125 features a simple and precise temperature control. The easy to use, digital display makes programming and monitoring easy. An Eco Select brand product means it saves electricity and water while reducing noise. Backed by a 1 year warranty.