RV Grey, Black, and Fresh Water Tanks guide

One of the key benefits of traveling in an RV is the guarantee of a clean, private bathroom and access to fresh water.  With this perk, there are some disadvantages.  Mainly, taking care of and emptying tanks that may holding less than clean water.  If you’re new to RVing, you’ll want to familiarize yourself with the 3 main RV water tanks pretty quickly. Get started here to learn more about the 3 main water storage tanks in an RV or Trailer.

As all experienced RV campers know, there are three main storage tanks in a camper or motorhome. These tanks are:

  1. Fresh water tank
  2. Gray water tank
  3. Black water tank

RV tanks - diagram

The diagram above outlines how fresh water travels through your camper or RV to one water holding tanks. These holding tanks make the RV camping experience a lot more civilized than, say, a trip into the woods with your backpack.

But along with the conveniences of having fresh drinking water, a hot shower, and a sanitary place for you to go to the bathroom, there are certain responsibilities you need to be aware of in order to keep your travels pleasant.

While there are a few exceptions to this rule, most RVs have three water tanks: clean water (also known as potable water), black waste water, and gray waste water. Failure to properly maintain any of these three water tanks can lead to trouble later down the road.

Hooking up Your Sewage Connector at the Campsite

When you pull in to a camp site, one of the first things you should do is hook up your sewage connector to the one provided. Even though you have it hooked up, do not open the valve until the tanks are full. You should never let the sewage flow straight from the tank. If you do this, the waste will harden due to a lack of water, and you will end up having to pay for a very expensive pressure cleaning job.

Fresh Water Tank

The clean water tank is typically the largest of the three tanks. It’s often made of corrosion-resistant metal, although some may feature a plastic like polyethylene.

When filling your RV’s clean water tank, you should use a certified potable water hose. This white-colored hose is recommended to avoid cross-contamination with waste water. As such, the potable water hose should ONLY be used with the clean water tank and not the black or gray water tank.

A large class-A motorhome or coach can have a fresh water tank with a capacity of 100 gallons or even more.  Smaller sized trailers will have a smaller tank around 25 gallons.  Your RV should have a sticker that will give you the specs and capacity of the tanks.

Filter your Fresh Water Source

The quality of fresh water around the country, specifically at campgrounds, can vary dramatically. If possible, always use a water filter in your water input line / hose to your fresh water tank. Many RVs have a basic water filter installed already.

These filters are there to block sediment particles and provide a better, charcoal-filtered water. Some campers purchase another water filter and attach a short piece of hose to it. This way, the water is twice-filtered, and if there is sediment, it will gunk up the cheaper, stock filter, not your high-quality one.  If your RV does not have a built in water filter, then I highly recommend attaching a simple portable filter to your potable water hose.

The water filter we use is the Camco 40013 Taste Pure carbon water filter.  This water filter is portable and fits directly on your fresh water hose connection.  The filter reduces bad taste, odors, chlorine and sediment in fresh water. 100 micron fiber filter. High-flow carbon filter with KDF to help prevent bacteria growth.  This product is relatively inexpensive and will last you a full season of camping.

How to Clean your Fresh Water Tank

Campers should always take the appropriate steps to avoid the growth of bacteria in their fresh water tanks. Your tank is in a dark place and is usually warm and wet, making it the perfect breeding ground for bacteria if preventative measures aren’t taken.

The best way to avoid bacteria growth, though, is to regularly dump your tank to avoid letting the water stagnate. All campers and RVs have a fresh water valve, making it easy to dump water when desired, and most campgrounds allow the dumping of fresh water at any time.

The easiest way to clean your fresh water tank is with a mixture of bleach and fresh water.  At a minimum, you should sanitize your fresh water tank at least once a year.  Here are the steps to clean your fresh water tank:

  1. Drain your fresh water tank.
  2. Mix one cup of bleach into a a one gallon jug and fill with fresh water.
  3. Pour the solution into your fresh water tank.  You can use a regular funnel.
  4. Close the fresh water valve.
  5. Turn on your water pump.
  6. Take your potable hose and attach to fresh water valve and fill your water tank.
  7. Now you want to make sure your grey water valve to the sewer connector is open.
  8. After the fresh tank is full, you will want to turn on each faucet and shower head in your RV / Trailer.
  9. When the water is running you want to wait until you smell the bleach in the water.  This will fill the line with the bleach solution.
  10. When you smell a strong bleach solution, turn off the faucet.
  11. Fill your fresh water tank.
  12. let the water sit in the tank for at least 4 hours.
  13. Now turn on each of the faucets / shower head in your RV and run all of the water through your lines until the fresh water tank is empty.
  14. Keep smelling and when the bleach smell is gone, you can turn off the faucets.
  15. You may need to repeat this step if you still smell bleach.

Black Water Tank

The black water tank is where waste water from the toilet drains. You should never attempt to drain your RV’s black water tank in a non-approved dumping site. Not only this is bad RV etiquette, but it could land you with a hefty fine, as most places have laws requiring RV operators to dump their black water in designated areas.

Furthermore, you should leave the black water tank drain valve closed until it approaches its maximum capacity.  Usually, when the tank level indicates 3/4 full, I will empty the black water tank. The general idea is to allow the solids ample time to break down so the water can be emptied more easily when you finally open the valve.

Purchase RV-Friendly Toilet Paper

RV tanks - toilet paper

The toilet paper you use in your camper must meet certain standards. When purchasing toilet paper, be sure the package says “safe for septic tank or RV use” somewhere on it. This means the paper breaks down quickly. I also recommend purchasing only single-ply toilet paper.  Walmart is a great place to buy your toilet paper.

One great way to make sure your toilet paper is RV-friendly is to test it. To do this:

  1. Place a few sheets of your chosen toilet paper in a cup of water.
  2. Wait an hour or so.
  3. After an hour has passed, cover the cup and shake it.
  4. The paper sheets should be shredded into pieces. If not, it probably won’t breakdown in your black water tank.

Use Plenty of Water When Flushing the Toilet

RV tanks - toilet

This is one area of RV tank maintenance where you do not want to be frugal with water. When you flush, make sure a decent amount of water is also sent into the tank. This water will help keep the excrement soft and help the toilet paper breakdown.  More water means you are diluting the residue by increasing the amount of fresh water in your black tank.

The toilet in many RVs has a foot pedal for flushing with two positions. If you hold it halfway down, water enters the toilet but does not flush. Once you press it all the way down, the toilet will flush. This allows you to manage the amount of water used with each flush.  It is actually fun to flush the toilet because you have full control of the amount of water.

Dumping the Black Water Tank

I will cover this more in depth later, but make sure to dump your black water tank first, close the valve, then dump your gray water tank. The gray water will help clean out whatever was left behind from your black water.

Gray Water Tank

The third type of RV water tank, gray water, is waste water that comes from the bathroom and kitchen sink. It’s stored in a separate tank because it doesn’t contain human waste.  Basically, all water except for the toilet will drain to the grey water tank.

Dumping Gray Water

Regardless of how frugal you are, eventually you are going to have to dump your gray water tank. Campgrounds do not allow the dumping of gray water onto the ground. It must be dumped at a dump stations, the same place where you will have to dump your black water tank.

The dumping connections for gray and black water are the same for all campers and RVs.

When you look in the service compartment, you should see three-inch connectors. On most RVs, the lines link to T-type connections with one common three-inch connector.

These connectors are there so you can easily connect a three-inch flexible hose that is designed to connect to the dump station’s inlet. This system is designed to minimize the opportunity for spillage and minimize cleanup.

How to empty / discharge your grey and black water tanks:

  1. Start with emptying the black water tank first by pulling the black water valve.  After you see or hear no more running water, close the black water valve.
  2. Next, open the grey water valve and empty the grey water tank.  Close the grey water tank valve.
  3. If you want, you can refill both tanks with more fresh water and repeat emptying the tanks.  This will clean out any remaining reside in the tanks.
  4. After you are done, disconnect the sewer hose from the outlet.
  5. On occasion we add water tank treatment to our tanks with running water.  When we drive back home, the chemicals will slosh around the tanks and clean them through agitation.  Don’t recommend this if you plan on storing your RV for some time.