I've gone through 3 Solo backpack sprayers in the last several years, and I'm getting tired of it. They develop leaks around the diaphragm, it runs down your back, drips where you don't want it to, etc. The main purpose is to spray round-up and an occasional post emergent for broadleafs. My question - has anyone found a superior backpack spayer in the 4 gal. range? I am not so concerned about price as I am quality. Any recommendations would be appreciated. What's the best one out there??????