RV SortFree to compare. No sign-up.

RV glossary · Water & holding tanks

Gray tank

Also called: Grey water tank

The holding tank for used water from the sinks and shower. Many RVs have more than one gray tank.

When boondocking, the gray tank often fills before the fresh tank empties, because nearly every drop from the sinks and shower ends up there. Washing dishes in a tub and taking quick showers stretch it.

Gray water is dumped at a dump station or sewer hookup, usually after the black tank, so the cleaner gray water rinses the sewer hose.

Try it on RV Sort

Related terms

Black tank
The holding tank connected to the toilet. It is emptied at a dump station or sewer hookup, typically before the gray tank.
Fresh water tank
The tank holding clean water for drinking, cooking, washing and flushing when you’re not connected to a water hookup. Water weighs about 8.3 lb per gallon, so a full tank adds significant weight.
Dump station
A place to empty an RV’s gray and black tanks through a sewer hose into an underground drain. Found at campgrounds, truck stops, rest areas and some fuel stations, sometimes for a fee.
Boondocking
Camping without hookups (no water, sewer or electric), often on public land. How long you can stay depends on your tanks, batteries and propane.

More water & holding tanks terms

Holding tanks · Sewer hose · Black tank flush · Macerator · Cassette toilet · Composting toilet · City water connection · Water pressure regulator

← All 178 RV terms