ISpring UVF55FS Whole House UV Water Filter with Smart Flow Sensor Switch, 55W, 12 GPM. [Whole House Water Treatment] As the UPGRADED VERSION of UV water filter iSpring UVF55, UVF55FS is a perfect last step to add to your whole house water filtration system and give you the peace of mind of knowing all of the water in your house can be treated at once. [Upgraded Ballast with Flow Sensor Switch] Ensured actual treatment with water’s long dwell time in the 37.5-inch 304SS reactor chamber; a 12 GPM flow rate and minimum pressure loss with 1-inch MNPT inlet/outlet design; a quality 55-watt UV lamp(UVB55FS) in durable quartz sleeve has a long bulb life of up to 9,000 hours; upgraded 55W ballast(UVT55FS) with smart flow sensor switch(3 modes: “Auto”, “Move”, “Stop”) makes it easy to control and monitor system performance. “Auto” is recommended to protect the UV lamp. The sensor will only kick on when the flow rate reaches 0.66 gallon/minute (2.5 L/m). [Easy Installation and Simple Maintenance] Mounting clips included for easy DIY installation. Annual replacement of the UV lamp and regular cleaning of the quartz sleeve(every 6-12 months) recommended to ensure optimal performance. [Chemical-free, Environmentally Friendly, Affordable, and Reliable]: A green alternative to chlorine treatment. Free of chemical byproducts. Build your trust in water for your entire household by removing risks unable to be addressed by your municipal treatment plant or those born with well water or other natural water sources.