Written by:

David Hosea

Last updated: March 13, 2024

When I first started RVing, it took me close to an hour to empty the black and gray tank. I was learning and didn’t want to make a mess, so I took my time. As I gained more experience, I reduced the time spent to about twenty minutes. Then, as I continued to gain more experience, the time I took to finish the chore grew again. Now, I’ll take as much as an hour (again) to empty the tanks. But I am doing more in that hour than I was at the beginning.

Everyone who owns, rents, or borrows an RV will learn how empty black tanks.  Gray tanks, too.  It is a straightforward process, but it is important to consider that emptying tanks can be messy if done incorrectly or incompletely.  In this article, we will discuss:

1. The supplies needed to thoroughly and efficiently empty holding tanks
2. A process that includes testing and preconditioning the sewer hose
3. Common mistakes to avoid.

But before we step through the process of emptying black tanks, let’s review what black tanks are and why we need to dump them correctly.

Black tanks hold toilet sewage, while gray tanks hold sink and shower wastewater. They are located low in RVs and vary from a few gallons to 50 gallons in size.

Emptying black tanks correctly is necessary for several reasons:

1. Prevents clogs: waiting until the black tank is nearly full will minimize solid accumulation and clogs in the tank piping and sewer hose. Empty tanks when there is enough water to create pressure and flush the waste.
2. Avoids unpleasant smells: emptying tanks when there is not enough water will lead to waste build up and will create unpleasant odors. This happens when campers leave valves open thinking that waste will drain completely like it does at home. It won’t, and it will allow waste to build up and create odors.
3. Prevents damage and leaks: waste build up and clogs can lead to damaged pipes and valves. Significant build up can create pressure inside the tank and pipes, and add enough stress that pipes, valves, and seals may crack or fail.
4. Complies with regulations: dumping black water on the ground is illegal. You can’t just dump the tanks anywhere. So, dump only at designated locations to avoid penalties.

The process itself isn’t difficult, although it can be a little unpleasant.  We’ll look first at a summarized list of the steps taken to empty the black tank.  Then, we’ll look at the tools and detailed steps.

How to empty the black tank in 16 steps: a summary

1. Plan to empty the black water tank when it is two-thirds full or more.
2. Find a dump station.
3. Gather supplies.
4. Connect the sewer hose to the RV’s sewer discharge.
5. Connect the discharge end of the sewer hose to an elbow.
6. Place the elbow nozzle into the dump station pipe, ensure a good seal.
7. Ensure that the black tank and gray tank valves are closed.
8. Open the gray tank valve for 5 seconds to test the connections and to precondition the sewer hose, then close the gray tank valve.
9. Open the black tank valve and allow the sewage to empty completely.
10. Flush the black tank.
11. Close the black tank valve.
12. Open the gray tank valve and allow the wastewater to drain completely.
13. Close the gray tank valve.
14. Disconnect the sewer hose and replace the cap on the RV sewer pipe.
15. Optional: clean the ends of the sewer hose and the elbow with soap and water, then disinfect.
16. Store the sewer hose and elbow.

Now, let’s break down these steps with a detailed list, providing you with a deeper understanding of each crucial aspect of emptying black tanks.

1. Plan on emptying the black tank when it is more than two-thirds full. The rush of water being emptied from a full tank creates pressure and dislodges debris when emptied. If there isn’t enough water in the tank, there isn’t enough water flow to thoroughly empty the tank.
2. Find a dump station: If you are not at a full hookup campsite, look for dump stations in the campground. Dump stations can be found at some gas stations and truck stops and some states provide dump stations at rest stops as well. RVdumps.com shows dump stations by map or by state, so check that resource if needed. Also, some RV parks will allow non-guests to dump their tanks for a fee.
3. Gather necessary supplies: Campground dump stations often have a line of RVs waiting their turn during peak season at check out time. Be considerate of others and have supplies ready to go so you can get through the process quickly.
   • Gloves protect your hands from waste. I prefer to use disposable gloves, so I don’t have to clean and store gloves used in the process.
   • Rhino Blaster: On board flush ports often access black tanks only allowing bacteria and mold to grow in the gray tank. The Rhino Blaster attaches to the RV’s sewer connection and flushes from the bottom enabling users to more thoroughly rinse both tanks.
   • Sewer support: A flexible sewer hose support creates a consistent downward slope. The continuous slope ensures that wastewater flows smoothly without getting trapped or stuck. The support also keeps the sewer hose off the ground and helps prevent damage from abrasion or punctures which will lead to leaks.
   • Sewer hose: This is a durable and flexible, 3-inch diameter hose that directs wastewater from the tank into the dump station’s sewer connection. They come in various lengths but are commonly 10 to 20 feet long when extended. Multiple sections can be connected to extend the pipe when needed.
   • Clear elbow: The elbow connects to the discharge end of the sewer hose and creates a seal with the dump station’s sewer connection. While not pleasant to look at, a clear elbow allows you to see when the tanks are finished draining.
   • Water hose: A water hose dedicated to non-potable water connects the dump station’s rinse water to the RVs flush valve. I use an orange, expandable hose because nearly all my non-potable water supplies are color coded orange. Color coding equipment prevents cross contamination.
4. Empty the black tank
   • Ensure that both tank valves are closed to prevent black tank waste from backing up into the gray tank.
   • If using the Rhino Blaster, remove the cap on the sewer connection, then connect the Blaster. Connect the sewer hose to the Blaster, or if not using a Blaster, connect the sewer hose directly to the RV’s sewer outlet.
   • Connect the discharge end of the sewer hose to the elbow.
   • Extend the sewer support and lay the hose on top ensuring an even slope. Make sure that there are no low spots to catch and hold waste.
   • Place the elbow in the dump station’s sewer connection and ensure a good seal.
   • Precondition the sewer hose: once the sewer hose is connected between the RV’s dump valve and the dump station’s sewer pipe, open the gray tank first for just a few seconds, then close it. This does two things.
     • If there is a leak anywhere, you will see it here and you can fix it. It is easier to recover from spilled gray water than sewage.
     • The soapy water in the gray tank will lubricate the sewer hose and help prevent solids from sticking.
   • The steps below describe flushing without a Blaster. I use this quick flush every time I empty the black tank. NOTE: if you have a line behind you at the dump station, skip this step and flush another time.
     • Connect a hose for non-potable water to the RV’s flush port. With the black tank valve closed, turn on the water to fill the black tank.
     • Monitor the tank level closely or use an inexpensive flow meter like this one to measure the amount of water going into the tank.
     • Fill the black tank to about 80%, turn off the water, and open the black tank valve again. The rinse water will drain and pull out some of the remaining waste. There will be more than expected.
     • Repeat until the rinse water from the black tank is relatively clear. It may never be completely clear, but at some point, it will be good enough.
     • Close the black tank valve.
5. Empty the gray tank
   • After the black tank is flushed and the black tank valve is closed, open the gray tank valve and allow the water to drain.
   • Close the gray tank valve.
6. Clean up
   • Ensure that the black tank and gray tank valves are closed.
   • Disconnect the hose at the RV’s sewer pipe and ensure that the end of the hose remains higher than the rest of the hose.  If the end of the hose drops below, then you will spill gray water.
     • Some RVers like to hold the end of the hose while dumping additional water to rinse.  In my opinion, sending gallons of gray water through the hose is sufficient.
   • Slowly lift the end of the hose and walk it all the way to the elbow to ensure that all water is drained from the hose.
   • Replace the RV’s sewer pipe cap.
   • Disconnect the sewer hose from the elbow and store both items separately from fresh water hoses and connections.
   • If black water or gray water spilled, rinse the area.
   • Disconnect the rinse hose from the flush port, store.
   • Clean or discard your gloves.
   • Wash your hands.
   • Add a few gallons of water to your black tank, then add the enzyme treatment of your choice.

What happens if you cannot empty your black tank?  Is it okay to travel with the black tank full?

It is okay to travel with a full black tank for a short distance.  RVers at camp sites without a dump station must travel to empty their tanks.  Also, some manufacturers recommend filling the black tank ¾ full, then driving for a while to agitate the contents and break up any dried solids.

We all get better with the process as we practice it.  But here are a few common mistakes we should all avoid.

1. Failing to test connections and precondition the sewer hose.  Connections that are not fully seated can come apart when the tank valves are opened spilling waste. 

I learned this the hard way.

While connecting the hose to the RV sewer discharge, I didn’t realize that one of the tabs on the hose missed the bayonet connector on the RV connection.  So, the hose connection was at an angle and I could not see the small gap that was open at the 6 o’clock position.  When I opened the black tank valve, sewage blew out of that gap.  Whoops.

Testing the connection by opening the gray water valve first will make clean up easier if the connection fails.  Also, the soapy water coating the inside of the sewer hose will help prevent black tank waste from sticking.

Emptying black and gray tanks in an RV is a non-event.  It is not pleasant, but if you consider the steps described above, then the process is just another chore that must be done.  Use the right supplies, the right process, and comply with regulations to avoid penalties.

I hope this article helps and I am curious to hear about insights you may have as well.  If you have experiences that we can learn from, please let us know.

Also, if you are curious about our thoughts on RV Toilet paper, read our last blog post.

Thanks for your comments and we’ll See you down the road!

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