Hi We are new to the RV lifestyle but it seems this problem is universal when dealing with water. On our yacht and in our Class A we had the same problem, our "FIX" is actually quite simple. we use standard water hose and than we purchased a 3/8 X 1/2 fitting which we attach a 3/8 black plastic hose to our water line, this we insert all the way into the tank, eliminating the water/air bubble problem on the fill fitting. the air can excape unrestricted because the tank fills from the bottom up instead of the fill down. we purchased the stiffer 3/8 black hose at home depot for around $6.00 and had enough for two hoses. it also helps with the burping of trapped air in the tank and the expulsion of water from the vent. hope this helped you....Dale & Jo Ring
