Is it leaking inside or outside?
If it is outside it is probably as SNOKING said...the hose connection.
Especially those cheapie Camco white hoses from WallyWorld or Camping World (I know...I have three of them).
Or it could be the city water inlet connection...
I recently had an inside leak on mine and I had to replace the hose on the back side of the city water inlet, and the water inlet as well.
Funny thing was that I was at an RV park in RV'ing heaven near Denver...
There were at least 10 dealerships with parts departments, most within walking distance...
Yet not a one carried that hose!
I wound up going to an Ace Hardware to get it...
If that is the case, make sure you take that hose with you and try it on one of their fitting thingies they have in the hardware department, then try the new hose to make sure both ends are compatible!
As for the outside city water inlet, I replaced the cheap plastic one with a much nicer (and more expensive - $40) brass connection!