Knife Gate or Pinch Valve?

[sportsnut44]

I need to provide a shutoff valve in a gravity flow storm drain piping system. Size ranges from 6" to 24". I commonly see gate valves specified on other projects, but I am concerned about their ability to properly seat with the potential for debris to be in the base of the piping. I am considering knife gate valve or a pinch valve as alternatives. Which is best for this application, and do you know of a link to a well known manufacturer of these valves? This is a buried application and I need to be able to use a 2-inch operating nut and flush mounted valve box due to traffic in the area. Thank you.

 

[cvg]

red valve pinch valve could work but are more often used for pressure flow

http://www.redvalve.com/rv/index.php/content/view/128/187/

waterman sluice gate

http://watermanusa.com/productdetails.asp?product=6