RV Grey Tank Guide
The grey tank holds water from your sinks and shower. Dump it at a dump station right after the black tank, so the soapy water rinses the sewer hose. It usually fills faster than the black tank, often every 2 to 3 days. Don't drain it on the ground unless a local rule clearly allows it.
Grey tank vs black tank
| Grey tank | Black tank | |
|---|---|---|
| Holds | Sink and shower water | Toilet waste |
| Dump order | Second | First |
| Valve at a full hookup | Can stay open | Keep closed until mostly full |
| Main problem | Food and grease smells | Solids build-up, clogs |
Some RVs have two grey tanks (kitchen and bath). Each has its own valve. Dump both after the black tank.
Making a grey tank last longer
- Take short showers and turn the water off while you soap up.
- Wipe or scrape dishes before washing, and wash them in a tub you can empty at the dump station.
- Use the campground bathhouse when you can.
- Fix dripping faucets. They fill a tank surprisingly fast.
Keeping it from smelling
- Keep food and grease out of the drains. A sink strainer helps.
- Run water in each drain every few days so the P-traps stay full and block sewer gas.
- After dumping, add a few gallons of water and a tank cleaner, then dump again on your next stop.
- Never pour grease down a drain. It hardens on the tank walls and sensors.
Frequently asked questions
What is an RV grey tank?
The holding tank for water from your sinks and shower. It is separate from the black tank, which holds toilet waste.
Can I dump grey water on the ground?
Usually not. Most campgrounds, parks and many states don't allow it, because grey water carries soap, food and bacteria. Unless a rule clearly says otherwise, empty it at a dump station or into a sewer hookup.
How often should I empty the grey tank?
Grey tanks fill faster than black tanks because of showers and dishes. Many RVers empty it every 2 to 3 days when they are not hooked up to sewer. Dump it right after the black tank so it rinses the hose.
Why does my grey tank smell?
Usually food and grease breaking down in the tank, or a dried-out P-trap under a sink. Run water in every drain, scrape dishes into the trash, and flush the grey tank with water and a tank cleaner now and then.
Can I leave the grey valve open at a full-hookup site?
Yes, but close it a day or two before you leave or dump, so you have a tank of grey water to rinse the sewer hose after the black tank. Keep the black valve closed until that tank is mostly full.