There are generally three different holding tanks on a fifth-wheel trailer. The first is a fresh water tank, the second a gray water tank and the third a waste tank. Gray water is from your sinks and showers. Waste water is from a toilet. The size of each varies depending on the manufacturer of the trailer.
Keystone is a manufacturer of 30 different models of fifth-wheel trailers. Their 26-foot 245RKS model has a 60-gallon fresh water tank, a 38-gallon waste water tank and a 76-gallon gray water tank. These measurements are consistent across most Keystone models.
Dutchmen is another manufacturer of fifth-wheel trailers. When dealing with Dutchmen models, holding tanks on smaller trailers are slightly smaller than those on larger ones. For example, the 30-foot 276RBS has a 52-gallon fresh water tank, 42-gallon waste water tank and 42-gallon gray water tank. The 34-foot 316FKDS, on the other hand, comes equipped with a 56-gallon fresh water tank, 42-gallon waste water tank and 84-gallon gray water tank.
