K-7 Unloader Surging

[HighTide]

Recently, my one year old K-7(.2) unloader starting surging VERY hard. You can hear the unloader pop loudly while the bypass hose whips up and surges the water into my tank every time you release the trigger. It's getting worse so is this the beginning of the end for it? Other than that, the K-7 works fine and I get pressure to near 3,500 psi when needed on my 5.6 gpm @ 3,500 psi set up. Is there a fix for this surging or time to order a new one?

Also, I like the soft touch unloaders as my guns and hoses have lasted longer since changing from a pressure type unloader. Is there another good replacement for the K-7 that can be mounted both vertically and horizontally? Thanks!

 

[Michael T]

On your bypass does it go to the pump or to a tank? The bypass needs a little more restriction to keep it from surging. What it does is sense flow and turns on , senses back pressure and turns off. Or you have a leak somewhere. Or you have a bad valve or seal. All or any could be the culprit.

 

[Steven Rowlett]

Is it going in and out of bypass too much? If so the orifice could need changing, they come in different sizes.

 

[HighTide]

It bypasses to the tank and only when I release the trigger. When going into bypass, it is so loud. Now, when I throttle down prior to shutting off machine, it goes into a repetitive bypass every second. It did work fine today while cleaning concrete for 4 hours and I was able to get 3,350 psi at the surface cleaner.

 

[Steven Rowlett]

It bypasses to the tank and only when I release the trigger. When going into bypass, it is so loud. Now, when I throttle down prior to shutting off machine, it goes into a repetitive bypass every second. It did work fine today while cleaning concrete for 4 hours and I was able to get 3,350 psi at the surface cleaner.

Sounds like the orfice needs to be changed to a different size, if I am right I would say a larger size.

 

[Russ Johnson]

It bypasses to the tank and only when I release the trigger. When going into bypass, it is so loud. Now, when I throttle down prior to shutting off machine, it goes into a repetitive bypass every second. It did work fine today while cleaning concrete for 4 hours and I was able to get 3,350 psi at the surface cleaner.

David, you should have a 5% bypass at all times with the K7. That's part of what softens the hit when you release the trigger. The surging at changing rpms is normal too. It's flow rated at certain ranges, and, as the speed decreases, so does the flow, throwing it out of its optimal range.