The others are on to something. You mention a "white hose" and from my experience, the white color NSF certified water hoses are very cheap vinyl with stamped and rolled ends. Rolled threads are bad news.
Look for a better, more expensive hose, with machined ends. You'll know by the weight and sharpness on the threads when you find the good ones. I have Camco's premium blue colored hoses with said ends.
Regarding washers, well with solid hose ends even the worst plastic washers work well. Then you bump up to decent flat rubber, then a bigger upgrade is using thick oring style washers. They don't work like an oring, but they can solve a lot of simple sealing issues when flat washers fail.
