What was once a mainstay in the "rural FD" community is rarely seen these days...but does still exist. The "Keystone" valve...as many old-timers might call it...is simply an external suction inlet control, butterfly-style valve. The "Keystone" terminology came from the brand of valve...similar to the notion of calling all facial tissues a Kleenex. In most instances the butterfly valve worked quite well and with little to no flow restriction. The advent of the piston-intake valve and the ball-intake valve for LDH seems to be what really "did in" the Keystone valve as the newer valves provide more features than just intake control.

Some of the big name fire service valve suppliers still offer a traditional Keystone-style valve. In terms of full-flow in a drafting situation, most of those 6-inch valves come with a 6-inch waterway, so we seldom see much loss in suction inlet performance. And, most of the manufacturers now offer more choices in valve control such as a geared hand wheel, air actuator, or electric actuator. The bottom line is there are a lot of choices when choosing a suction inlet control....research the design and performance capability of each before making the final selection. The Keystone valve is an old concept but still works well for drafting.