he ST66 Chemical Metering Valve with a red knob and numbered control points is designed to regulate chemical flow in pressure washing systems, including Ehrle models. It features two 6mm plastic hose barbs for chemical pickup, allowing users to switch between two chemical sources. The red adjustment knob enables precise control over chemical dilution rates, enhancing cleaning efficiency.

This valve is commonly used in hot water pressure washers for chemical dilution. Its design allows for easy switching between different chemicals, making it versatile for various cleaning applications.