Here is a very low tech method that has served us well.
We buy a 6 gallon blue water jug (WITH HANDLE) at home depot.
Remove the top and carefully cut out the "puncture" hole.
Using an exacto type blade make a tiny air hole in the cap.
(to speed things up)
Insert a long vinyl tube and reattach to the jug.
Invert and use gravity to transfer the water.
To be honest we have since bought a manual "bilge pump" that fits those neck openings to pump it right into the tank.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW