Hi Al from K4 land,
I have 2 suggestions to supplement Lewster's expert answers.
1. Check the male end of the supply hose. One small ding and you can have a leak. I have replaced the thin brass fittings with NSF approved potable (sic) replacement fittings ( hard to find) or ( if you are not cheap like me ) just get a new hose.
2. Install a new washer in the female end of the "city" water connection, one without the any gripper molded "teats" in the outside diameter; these are a bit better at sealing. Personally I use a female washer with a integral stainless steel cone screen ( ine mesh) pointed towards the hose to keep the big stuff out of the system - it has a wider face and seals better.
I get these from the local farm store; they are used for drip irrigation systems.
Hope this helps
WLJ 1943 - Warren (from K6/K7 land).