The Notorious RV Gray Water Tank
For boondockers and dry campers, the gray water tank is usually the absolute limiting factor for how long a trip can last. Because modern RVs tend to have fresh water tanks that are larger than their gray water tanks (especially travel trailers), you will almost always run out of gray tank space before you run out of fresh water.
What Exactly is "Gray Water"?
Gray water is all the wastewater generated in your RV that does NOT contain human bodily waste (feces or urine). The sources of gray water in an RV are:
- Shower drain: Soapy water, hair, dirt from washing.
- Kitchen sink drain: Food particles, grease, cooking water, dish soap.
- Bathroom sink drain: Toothpaste, mouthwash, hand soap.
Why Your Gray Tank Fills So Fast
Unlike the black tank (which only receives quick flushes from the toilet), the gray tank takes the brunt of continuous water usage. If you leave the faucet running while brushing your teeth, that's a gallon down the drain. If two people take standard 5-minute showers, that's easily 8-10 gallons.
If your camper has a 40-gallon fresh tank and a 30-gallon gray tank (a common configuration), and you use all your fresh water through the sinks and showers... your gray tank will overflow with 10 gallons of water left still sitting in your fresh tank. You must manage gray water aggressively.
Pro Tips: Managing and Reducing Gray Water
1. Catch the Cold Water
When waiting for the shower water to get hot, don't let the cold water run down the drain. Catch it in a pitcher or bucket. Use that clean water to flush the toilet or boil for coffee later. This saves fresh water AND gray tank space.
2. Wipe Dishes Instead of Rinsing
Wipe off sauces, grease, and food chunks from plates using a paper towel before washing them. This keeps food solids (which rot and smell) out of the gray tank and drastically reduces the water needed to rinse.
3. The Dishpan Method
Place a plastic dishpan in your sink. Wash and rinse your dishes over the pan. When you are done, you can carry the dishpan outside to dump the water over a campfire or disperse it (if local regulations allow it).
4. Stop Washing Down Food
RVs do not have garbage disposals. Using your kitchen sink to wash down rice, noodles, or grease will result in a gray tank that smells worse than your black tank. Use sink strainers religiously.
Can You Just Dump Gray Water on the Ground?
Legal Warning: In most state parks, national parks, and established campgrounds, dumping gray water on the ground (no matter how biodegradable your soap is) is strictly prohibited and carries heavy fines.
On Bureau of Land Management (BLM) land or National Forest land (dispersed camping), regulations vary wildly by state and local ranger district. While some extremely remote areas permit dispersing small amounts of gray water to water vegetation, you should always assume it is illegal unless you have explicitly verified with the local land management agency. Never dump gray water near streams or water sources.
What About the "Blue Boy" Portable Tanks?
If your RV's gray water tank is hopelessly small for your family size, consider purchasing a portable waste tote (often called a "blue boy"). These wheeled tanks (15-35 gallons) allow you to hook up a hose to your RV, empty the gray tank into the portable tote, hitch the tote to your truck, and pull it directly to the campground dump station without having to completely break camp and move your RV.