To be more precise, the component at the input end of the flex hose is a small anti-backflow valve. To find it you have to disconnect the flex hose from the tap. On the underside of the tap there are 3 connections: cold input, hot input and an output connection to the flex hose. A small open-ended wrench is needed to remove the flex hose. It was an awkward job on my 2012 R27. The only reason the valve was originally put in place is prevent the very unlikely occurrence of water in the sink being drawn back into the supply. That would require some sort of siphon condition. Let’s see, the spray handle submerged in sink water, the tap open, the water pump turned off (no pressure) and water drainage from a supply connection lower than the spray head. A known, and experience action, is for the valve to act as a crude filter. When I did the repair, about 10 years ago, I removed but did not replace the valve.