A "gallon pail" refers to a container that can hold one gallon of liquid or substance. It is typically a round bucket-shaped object with a handle used for carrying or storing liquids such as water, paint, or cleaning solutions. Full definition
Used for bulk filling of 5 gallon pails by volume only. (fillers.com)
This type of unit must be attached to an incoming water source and does require at least 3.5 gallons per minute of water flow to create the suction needed in the gallon bottles (if you can fill a five - gallon pail in 90 to 100 seconds, it should work). (petbusiness.com)
I use the Dutch Boy interior white and antique white for everything except accent colors and am happy with the price, (70 bucks for 5 gallons), the five gallon pails with the sky blue label. (biggerpockets.com)