What is “Grey Water?”

If you have never gone RVing and are just starting out, this is another term you will hear regarding the water in your RV. Grey Water is essentially the water you have used from your sinks and tubs. This water is held within a holding tank until it is released by the RV owner. A good thing is that this water can be repurposed, something we will discuss in a moment.

Grey Water will be held in a separate holding tank from your Black Water. You will also need different accessories for your Grey, Fresh, and Black Waters.

Quality / Quantity

Grey water will contain different quantities of mineral and excreted human fluids. For example, if you use your sink for brushing your teeth. The grey water could contain the waste toothpaste along with any bacteria brushed away. Grey water can also contain any dirty wash from a person while using the shower.

When you purchase an RV you should look for the quantity of grey water your RV will hold. This will come in handy while you are traveling if you plan to boondock. Keeping in mind that water weighs approximately  8.34 pounds (lb) or 3.785 kilograms (kg) for each gallon. Depending on the mineral within your grey water, it should not weigh much more.

Keep all this in mind when you think of your tow weight. If you have a 40-gallon tank that is half full, you will have an added approximately 166.8 pounds (lbs) or 75 kilograms (kg).  Also, keep in mind that the longer you have grey water in the tank, the more it will deteriorate based upon temperature and minerals within the water.


Grey Water can be reused or reclaimed.

The grey water can be reused for things like watering plants. The minerals within the grey water can work as a fertilizer for your plants. Grey water can also be used for flushing your toilet to save your fresh water for other needed uses.

Reclaiming the grey water takes some work and special equipment. There are a number of water purification tools on the market. This could be another option to help you stay in your boondocking location a little longer.

Learn More > “What is RV Grey Water?”