Whether you are new to owning and operating an RV or you are a seasoned RVer, one of the more important things to understand is the difference between black and gray water tanks on your RV. Whether you own a camp trailer, fifth wheel trailer, or motorhome, the difference between the two tanks is the same - and equally important. 

You may have heard horror stories about someone detailing with their tank, or unfortunately, may have experienced something yourself. The key to avoiding any type of negative experience with the water held in these tanks is not only straightforward but easier to manage than you might think. 

Black Versus Gray Water Tank

The black tank holds all the human waste from your trailer or RV. It has its own separate holding tank, and must be disposed of at RV dump sites very carefully. The black tank on your trailer or RV is only for holding human waste.

The gray tank holds any and all wastewater from your trailer or RV - this is primarily water that drains through the various sinks in your RV. This includes your kitchen sink, bathroom sink, and if you have one, your outdoor kitchen sink. While there is still some bacteria in the gray tank water, it is nowhere near as important to manage as the water from your black tank. 

Understanding Your Onboard Tank Monitor 

In your trailer or RV, there is an onboard monitor that shows the fill level of your water tanks - typically the freshwater tank, gray tank, and black tank. Typically this monitor measures tank capacity in increments of thirds. 

If you feel that your tank monitor is not reading properly, try flushing the tank. Often times, debris such as toilet paper can interfere with the tank measuring process. 

Dumping Your Black and Gray Tanks

When it comes to dumping (draining) your black and gray water tank on your new RV, there is indeed a process to follow to ensure that the tanks are drained correctly (and safely). 

It is recommended that you drain your black tank first, while hooked up to some type of trailer dump station. Never drain this tank onto the ground. Using your sewage hose, connect the black tank outlet into the trailer dump station, and first drain your black tank. 

Next, drain your gray tank after the black tank has finished draining. This will ensure that any leftover debris from your black tank is cleared from your sewage hose. 

Now, after the gray tank has drained, connect your water hose to flush both tanks. Let that water run for 10-15 minutes until each tank is completely rinsed. If your trailer or RV does not have an option to flush the tanks, there are various tank cleaning chemicals that you can use to achieve the same result. 

And finally, if you are in a campground or RV resort that offers sewage hookups, always leave your black tank closed until it is time to drain the tank. Leaving the black tank does not allow for the proper buildup needed to thoroughly drain your tank. 

RV Insider Tips for Black and Gray Tank Maintenance

If the water in your gray tank starts to have a foul odor, pouring a small amount of dish soap into your tank will assist greatly in breaking down any residual buildup of food particles or grease that has formed in your tank. 

Make sure to never use any chemicals not designated for tank cleaning or maintenance. Examples include antifreeze, laundry detergent, or windshield wiper fluid. Over time, these chemicals can destroy the seals inside your tank, leading to even greater issues - leaks. 

Additionally, ensure that you use only RV toilet paper. Normal toilet paper does not break down as quickly and effectively as RV toilet paper, leading to possible clogs, or issues with the reading of your tank level on your tank monitor. You can find a local RV dealer here.

Finally, make sure that you place chemicals in your black tank at the beginning of any trip. These chemicals (sometimes sold as a dishwasher-type pod) help with odor elimination as well as breaking down some debris that is trapped in your tank.