jsuchar 14 Report post Posted July 11, 2010 I have a CAT 66DX40G direct drive pump, The pump is rated at 4000 psi at 4 gpm. The bypass valve went bad and I am replacing it with a K7-1 unloader valve. The original pressure tips were 4.5 size. They would not work properly, so I was advised to use 5.0 size tips. These seemed to work well, but another person advised me to use 5.5 tips. I am working at 3000 psi. I am confused as to which tips to use. Can anybody help me? Thanks in advance. Share this post Link to post Share on other sites
Jerry 24 Report post Posted July 12, 2010 (edited) The Giant #22654A would have been a better fit, as it would allow the 4000 psi you were looking for, but.. You should be using a #4.5 spray nozzle to get 4gpm@3500psi to get the K-7 to do it's rated 3500psi ..IF you match the K-7 outlet oriface ..to the flow which allows it to actuate when the gun is opened.. If you have "flow-restrictions" after the unloader, like over 75 ft of HP hose attached, a down-stream chemical injector, or "unusual back-pressure" in the heater-coil (like scale build-up), ..you might need to put a #O outlet oriface in it, ..to "recognize" you have opened the trigger-gun. To prove this is the issue, take a pair of pliers to the bypass hose, squeezing off the flow a little.. This forces more water out the outlet when the trigger-gun is open, thus forcing the valve to actuate. ..Just don't force the bypass hose to blow-out. Eh? If this sounds like a pain in the schedule, Know this.. The Flow-actuated unloaders work the BEST, in several ways. Once you get it adjusted, it can last MANY years, with a LOT less stress on your system. Respect the tech.. you need one occasionally. Edited September 5, 2010 by Jerry sp. Share this post Link to post Share on other sites
