RV Gray Water

What is Gray Water?

RV gray water (or “grey water”) is the water collected from the drains of RV appliances other than the toilet. Any liquid runoff collected from drains such as the sink, dishwasher or shower becomes gray water and is stored in the gray water tank. It is called gray water because the mixture of soaps and other waste products turns gray after a short period in the tank.

Understanding RV Gray Water

Motorhomes generally have three holding tanks for water: (1) fresh water tank, (2) gray water tank, and (3) black water tank:

• The fresh water tank holds the clean water for use in the shower, sink, dishwasher or for other fresh water uses; 
• The grey water tank holds the dirty water from the RV shower, sink and dishwasher; 
• The black water tank holds human waste and other content that flush down the toilet. 

The RV gray water system serves a number of purposes including: (1) storage of gray water (2) delivery of gray water to the gray water tank, and (3) means to drain the gray water tank.  

The majority of RV gray water systems use a tank or closed container on the underside of the RV to hold the gray water. However, in some smaller RVs like campervans a simpler system may allow gray water to drain into a container placed outside the van on the ground. 

Emptying the Gray Water Tank

When the indicator light on the instrument panel shows the gray water tank is full, it’s time to locate a sewer dump station. If at a full hookup campsite, this should be located near the other utility hookups. Otherwise, a site map or camp host will direct you to the location of a public use dump hole. 

When emptying the gray water tank, put on latex gloves and protective eyewear to protect from accidental splashes. Using a dedicated gray water dump hose, remove the dump valve cover and connect the hose from the valve to the dump hole. The end inserted into the hole will usually have a clear elbow, so it can be seen when the tank is finished draining. 

Open the valve for the black tank first. When the black tank is finished draining, close that valve and open the one for the gray tank. Then, rinse the inside of the hose with fresh water and store it in a tub with a locking lid.

Only empty the RV gray water tank into specially designated sewage receptacles. While it may be permissible in some areas to empty gray water on the ground, it is not environmentally friendly and is frowned upon by fellow campers. 

RV Gray Water Holding Tank Maintenance

Regular maintenance is required to keep the grey water tank in proper working order. In most recreational vehicles, an instrument panel monitors the fill levels of each water tank. It is recommended to empty the water tanks when they are full or close to full, as the increase in water pressure helps clear debris that may get caught in the pipes.

The most common issue that occurs with gray water tanks is foul odor emanating from the drains. Gray water tanks may contain hair, grease and food particles that can build and cause odors if not properly maintained. 

Taking simple preventative maintenance measures will ensure that the grey water tank remains clear and free from odor. 

Cleaning the Gray Water Tank

Keeping the gray water tank clean is straightforward. Everyday use of sinks and showers is enough to keep it clean, however, home cleaning solutions or chemical additives can be purchased to help with build-up and to keep things smelling fresh.

Note that if using chemicals, gray water tanks don’t need the same type of harsh chemicals as black water tanks. It’s important to use an appropriate gray water tank cleaner and follow the instructions for correct usage.

If you choose not to use chemicals, you can simply clean your grey water tank by repeatedly rinsing with warm, soapy water. Another method is to use a heavily diluted bleach solution if germs concern you. 

A clever RVing hack used by some campers is to pour ice cubes into the holding tanks and then drive short distances. The motion of the RV will agitate the ice, which helps to clean sensors and remove debris from tank sides. Once the ice has melted, it can then be emptied easily from the tank. 

Storing the Gray Water Hose

The hose used to empty dump the RV tanks should be stored with care. Oftentimes, the same hose is used for gray and black water dumping. Even when thoroughly rinsed care should be taken as the gray water hose may carry harmful bacteria. Keep the hose in a secured bin that has been regularly cleaned and/or sterilized. 

Related RV Terms

For related RV terminology, please reference the RV definitions below:

• RV Black Water: Waste collected from an RV toilet, which is stored in the black water tank.
• RV Fresh Water: Clean, drinkable water pumped into the RV from an outside source or stored in the fresh water tank. Supplies faucets and showers. 
• Full Hookup: A campsite with amenities to connect an RV to fresh water, electricity and wastewater dumps.
• Shore Power: The connection of electricity to the RV from an outside power source like a campsite’s electrical pedestal.