Understanding your RV's holding tanks with the what, where and how.

Understanding everything about your new RV takes time and resources. Keystone RV continues to provide information at your fingertips with the First Time Camper Series. Master Technicians, Matt and Bart explain everything you need to know about your RV Holding Tanks and provide some quick tips on maintenance. They discuss and answer: What are they? Where are they located? and How to use and take care of them.

What are the holding tanks in my RV?

Fresh Water Tank—The fresh tank is equipped with a gravity fill hose, a supply for the water pump, and a fresh tank vent to prevent the tank from swelling when full. It also has a low point drain which allows the tank to be emptied for winterizing or servicing. Use potable water only in the fresh water system.

Gray tank—A gray tank is used for kitchen sink waste water and shower water. Depending on the unit it may have multiple gray tanks. In our example, you can see we have a gray water inlet on the top. You may have a couple of inlets depending on the floor plan. A vent opening goes to the roof of the RV. This vents the tank and removes unwanted odors as well as prevents pressure buildup and swelling. The tank will have a termination valve as seen in the video.

Black Tank—Just like a gray tank we have the inlet on top however this inlet is for the toilet. The black tank also has a vent opening going to the roof of the RV. Again vent the tank and remove unwanted odors and pressure build-up. And finally the termination valve. You may see this in several configurations but they all do the same job.

What are some common similarities between the holding tanks?

  1. The fresh tank is designed to carry fresh water toward the pickup. The gray and black tanks are sloped to carry the waste water to the termination. This is important to know when leveling the RV.
  2. These holding tanks all have sensors and a wire harness, which are connected to the monitor panel inside the RV. The monitor panel reads the level of water inside the tank and is measured in thirds.
  3. Some tanks have “tank heaters” on them; this will vary by brand.  Not all brands install these.  In case you don’t know, tank heaters can be turned on to help prevent the liquid in the tanks from freezing.

Where are the tanks located on my RV?

The tanks will be in different locations depending on your floorplan and in some cases, the fresh tank may be installed above the floor, usually in a cabinet, under a bed frame, or as part of a pass thru storage area. You will also notice the overall shape is designed to nestle in between the frame rails of the RV below the floor. Sensors and a wire harness will be connected to the monitor panel inside the RV. Once again, the monitor panel reads the level of water inside the tank and is measured in thirds.

Important note: All terminations are on the driver's side of the RV usually from the middle to the back of the RV. This is important to know for campsite preparation as it helps determine whether you have to back the RV into the site, or if it’s a pull thru site.

What do I need to do to use the holding tanks?

We talk about these key points in our First Time Camper series-Introduction: Know your RV before heading out if you wish to refer and review.

  1. Add the proper amount of tank chemicals to your gray and black tanks before using and after dumping.
  2. Use plenty of water each time you flush the toilet; do not be afraid to use lots of water. We can’t stress this enough! Whether you are dry camping or at a campground with full hookups, you will need to use lots of water for a good flow when dumping your tanks.
  3. Use RV toilet paper, as it is a single ply and dissolves quickly.
  4. If you are camping and using Full Hooks Ups, meaning you have an onsite dump station, DO NOT leave termination valves open. Leaving the termination valve open when solids are flushed allows the water to run off into the dump station, and the solids will stick to the bottom of the tank and build up. This can lead to problems such as clogs, faulty readings of tank levels, and bad odors. Once again, please be sure to leave the termination valves closed until the tank level warrants dumping.

How do I maintain my holding tanks?

Fresh tank tips—Keeping the fresh water system clean and free of any potential contaminations should be a top priority. Sanitizing the system before using it for the first time and annually thereafter, or whenever water remains unused for prolonged durations, is recommended. This will help keep the water system fresh and discourage harmful bacterial or viral growth. Maintenance of your fresh tank is a must. 

Gray and Black tank tips—Maintenance on these tanks require the use of a tank deodorant and occasional cleaning.  When it comes to tank deodorants there are several on the market just be sure to follow label directions from the manufacturer on its proper use and amount and when you camp. Dirty tank probes will cause false readings at the monitor panel.  Keeping the tank probes free of debris requires proper use of deodorant chemicals, plenty of water, and a Black Tank Flush will help this happen for you. 

We recommend you read Chapter 10 of the Owner’s Manual where you will find helpful information and step-by-step instructions for maintaining your Tanks!!

Happy trails and happy tanks. We hope this helps you understand your tanks a little better and how they work and what steps to take to keep them performing well.

Notice: Do not leave the RV unattended during these processes and make sure the black tank termination valve is open and your sewer hose is connected to an approved dump station. Overfilling the black water tank will result in water overflowing on the roof of the RV thru the tank vent or into the interior of your RV from the toilet when the foot pedal is depressed opening the ball valve and the resulting damage is not covered by warranty.