Holding tanks for Recreational Use Vehicles are permitted through a state and local waiver process. The lot must meet minimum land area requirements per WAC246-272A-0320 (5)(e)(iii) in order to qualify for this waiver.  The vehicle must be licensed and able to be moved. All liquid waste water, including grey water, must not be dumped on the ground or in surface water.

A Mason County Certified Installer must install the RV holding tank. The tank must be on the Washington State Department of Health Registered List of Sewage Tanks and be at least 1200 gallons. The tank must be installed with audio & visual alarms and risers.

Holding tanks are not allowed for park-model trailers. They require a complete on-site sewage system.