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How to Dump Your Black and Gray Tanks

The order, the hose, the valves and what to put down the toilet. Dumping your tanks the right way, step by step.

What the two tanks are

The black tank holds the toilet. The gray tank holds the sinks and shower. Each has its own valve handle, usually near the sewer outlet on the driver side.

Some RVs have two gray tanks, one for the kitchen and one for the bath. Each one has its own handle.

Dumping, in the right order

Put on gloves. Keep a pair just for this job.
Take the cap off the outlet and connect your sewer hose. Twist it until it locks.
Put the other end in the dump station inlet. Weigh it down or use a fitting so it cannot jump out.
Pull the black valve first. Let it drain until it stops.
Close black, then pull gray. The soapy gray water rinses the hose on the way out.
Close gray. If you have a black tank flush inlet, hook up a separate hose and rinse the black tank until the water runs clear.
Take the hose off the RV end first, lift it to drain, then rinse it and put the cap back on.

Keeping the black tank happy

Keep the black valve closed at a campsite, even with a sewer hookup. The tank needs liquid to carry the waste out. If you leave it open, liquid drains and solids stay behind and harden.

Put a few gallons of water in the black tank after each dump. Use RV toilet paper or any paper marked septic safe. Nothing else goes down the toilet. No wipes, even the ones that say flushable.

When the gauge lies

Tank sensors read wrong when paper sticks to them. A tank that shows full after a dump is usually just dirty sensors. A long rinse, or a drive with water and ice in the tank, often clears them.

When to call a shop

Call a shop if a valve handle will not move, a tank will not drain, or you smell sewer inside with the tanks empty. That last one is often a dry trap or a failed vent.

The maker's own manuals

These guides cover how most RVs work. Your own rig may differ, so check the manual for your make and model.

Forest River · Owner manuals and component manuals
Keystone · Owner manuals by year
Every maker we link to

Renting from us? Call or text 909-259-RVDR before you try a fix. We would rather talk you through it than have you guess, and it is free.

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