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RV Black and Gray Tanks: Sewer Setup, Dumping, and Maintenance


Your RV’s black tank collects toilet waste, while gray tanks collect wastewater from sinks and showers. Keep the black-tank valve closed between dumping, use adequate flushing water, and empty the black tank before the gray tanks. Secure sewer-hose connections and routine cleaning help you manage wastewater while reducing buildup and odors.

What Equipment Do You Need?

  • RV Sewer Hose and Compatible Fittings: Connect the RV outlet securely to an approved sewer inlet.
  • Clear Sewer Adapter: Helps you observe discharge without disconnecting the hose.
  • Safety Glasses and Protective Gloves: Help protect against wastewater splashes and contact.
  • Dedicated Rinsing Hose: Keep wastewater equipment separate from drinking-water hoses.
  • Compatible Holding-Tank Treatment: Use the product and dosage specified for your tank system.

How Do RV Black and Gray Tanks Work?

  1. Black Water Tank: Holds toilet waste and flushing water until you empty it.
  2. Gray Water Tank: Holds wastewater from sinks and showers. Some RVs have multiple gray tanks, including a separate galley tank.

Drain lines carry wastewater into the tanks, and vents help manage gases and pressure. Sink and shower P-traps hold water to help block odors from entering the living space.

Termination valves control discharge from each tank. Valve handles and sewer outlets are commonly on the driver’s side, or roadside, but locations vary. Identify every valve and outlet before your first hookup.

How Can You Reduce Buildup and Odors?

  1. Keep the Black Valve Closed Between Dumping: Leaving it open at a full-hookup campsite allows liquids to drain while solids remain behind. Keep gray valves closed between dumping as well so you have water available to rinse the sewer hose afterward.
  2. Use Adequate Flushing Water: Add water to the toilet bowl before flushing and use enough to move waste into the tank. Too little water encourages accumulation.
  3. Use RV-Safe Toilet Paper: Choose rapidly dissolving paper suitable for RV systems. Do not flush wipes, paper towels, or hygiene products.
  4. Use Compatible Treatments: Follow product instructions for dosage and added water. Treatments may help manage odors and waste, but they do not replace proper flushing, dumping, or cleaning.
  5. Monitor Tank Levels: Empty tanks before they overfill. Monitor-panel readings are approximate and can be affected by residue on sensors.

How Do You Dump Black and Gray Tanks?

Wear gloves and safety glasses, and follow the disposal facility’s rules. Never discharge wastewater onto the ground or into a storm drain.

Step 1: Check the Valves

Confirm that all termination valves are closed before carefully removing the sewer-outlet cap. Residual liquid may remain behind the cap, so position yourself to avoid contact.

Step 2: Connect the Sewer Hose

Attach the hose securely to the RV outlet and the approved sewer inlet. Use the required adapter or retaining arrangement at the disposal point.

Support the hose to provide a downward slope without kinks or deep low spots. Confirm both connections before opening a valve.

Step 3: Empty the Black Tank

Open the black-tank valve and allow the tank to drain. Watch the discharge rather than relying on a fixed time; tank size, contents, and hose arrangement affect drainage.

Once draining is complete, close the black-tank valve.

Step 4: Empty the Gray Tanks

Open the gray-tank valves one at a time, allowing each tank to drain before closing its valve.

Gray water helps rinse black-water residue from the sewer hose, but it does not sanitize the hose.

Step 5: Close, Rinse, and Store

Confirm that all valves are closed. Rinse the sewer hose using designated facilities, drain it, disconnect it carefully, and replace the RV outlet cap.

Store wastewater equipment separately from potable-water supplies. Remove gloves and wash your hands thoroughly with soap and water.

How Do You Prepare the Tanks for Continued Use?

After dumping, add water and compatible treatment as directed for your tank system and product. Follow the separate winterization procedure when preparing for freezing conditions.

If odors, poor drainage, or inaccurate readings persist, clean the tanks according to their instructions and have unresolved problems inspected.

Review the wastewater instructions in your Keystone Owner’s Manual before your next hookup.

Disclaimer: The information contained in this article is deemed to be true and accurate at the time of publication. However, due to the evolving nature of our products and services, there may be changes or updates that occur after this article was published. We encourage users to verify the contents and consult with their dealer or Keystone RV for the most current information. If you have any questions or require further clarification, please do not hesitate to contact your dealer or reach out to Keystone RV directly.