How Do You Empty RV Holding Tanks the Right Way?

Most RVs have a fresh-water tank, a gray tank (sink and shower water) and a black tank (toilet waste). Dumping them is simple once you’ve seen it done, but where you dump and what you put in the tanks affects campgrounds, septic systems and ground water.

Where are you allowed to dump?

Use a designated RV dump station or a full-hookup campsite’s sewer connection. The EPA’s alert for RV owners warns that disposing of holding-tank waste illegally can create health and environmental hazards. Campground maps and Recreation.gov listings show which campgrounds have a dump station (see our booking guide).

What does the EPA say about tank chemicals?

• Some odor-control products contain chemicals that may pollute water resources when the tank is emptied into a septic system.
• The EPA names formaldehyde (also called formalin) as an active ingredient in some deodorizers and calls it a probable carcinogen; it can kill the bacteria a septic system needs.
• It also lists para-dichlorobenzene, heavy metals such as zinc, and other solvents among chemicals to beware of.
• If you must use a deodorizer, the EPA says to read the label carefully, notes that biodegradable (enzyme and citrus-based) products are available, and says to add no more than the recommended amount.
• The EPA also suggests using rest-stop facilities when you can, to reduce the need for deodorizers.

What shouldn’t go in the tanks?

The EPA’s fact sheet lists items that cause problems, including diapers, cat litter, cigarette filters, coffee grounds, grease, household chemicals, gasoline, motor oil, pesticides, antifreeze and paint. It warns that some products sold as “flushable,” like some cat litter, can clog hoses and septic tanks, and says to use toilets for waste and toilet paper only.

What’s a simple dump-station routine?

1. Read the dump section of your RV’s owner’s manual first; valve layouts differ.
2. Wear disposable gloves and keep a separate hose for rinsing (never your drinking-water hose).
3. Connect the sewer hose securely to the RV outlet and the dump-station inlet.
4. Open the tank valves in the order your manual gives, and let each tank drain fully.
5. Close the valves, rinse as your manual and the station allow, then disconnect and cap the outlet.
6. Rinse the area with the station’s non-potable water and wash your hands.

What if something spills?

The EPA’s sheet says to report sewage spills and other health hazards to the local health department and to keep people and pets away. At a campground, tell the host or staff right away.

Renting? Ask for a dump demonstration at pickup, part of our first-rental checklist.

What gear do you need at the dump station?

• Disposable gloves.
• A sewer hose in good condition, with secure fittings at both ends.
• A separate hose for rinsing, kept apart from your drinking-water hose.
• Hand soap or sanitizer, and a bag for used gloves.

Label the rinse hose so nobody uses it for drinking water.

Which tank do you dump first?

Follow your RV’s owner’s manual. A common routine is black tank first and gray tank second, so the gray water rinses the hose after the black tank empties. Close both valves before you disconnect the hose, and rinse the hose and the dump-station area as the station’s posted rules allow.

What should renters ask?

• Which tank chemical the owner uses, and whether they want you to add it after dumping.
• Whether the tanks must be empty at return, and any fee if they aren’t.
• Where the valves and tank level monitors are, and how accurate the monitors are.

What are the common mistakes?

• Pulling the valve before the hose is secured at both ends.
• Using more chemical than the label says.
• Putting wipes or “flushable” products in the black tank.
• Dumping anywhere other than a designated dump station.

How do you keep fresh water separate?

Many dump stations also have a potable water fill. Use only your drinking-water hose there, and don’t let its end touch the ground or the sewer inlet. Read the station’s signs, since some separate the rinse water from the drinking-water fill and mark which is which.