As RV owners, we don’t think about emptying our tanks — other than it being something we never look forward to! But how well do you know – and follow – the correct process for emptying your RV’s waste holding tanks? Whether it’s time for a refresher, you’re just double-checking your process, or you’re not 100% sure you’re doing it right, here’s all you need to know to dump your RV’s holding tanks properly, without problems, and to keep those tanks clean, healthy, and working properly.

First, a warning
Human waste and sewage is nasty stuff. In fact, according to the Occupational Safety and Health Association (OSHA), human vomit and feces are defined biological material that poses a potential threat to the health and safety of humans, animals, or the environment. In other words, it’s a biohazard. What makes exposure to these body fluids so risky? For one, blood and certain body fluids can be contaminated with bloodborne pathogens, infectious microorganisms that can cause disease in humans. So be extra careful when emptying your holding tanks. For more info, out our recent article.

What your tanks are and aren’t
Your RV’s holding tanks are just that — tanks that simply hold water until it is time to empty them. They are not a septic system. There is no need to break anything down, like with chemicals, enzymes or bacteria. Your tanks will not be full long enough for these processes to take place and if they are, you’re asking for problems. You’ll want to empty those tanks every two to four days — more often if they fill up quicker.

Get ready
You probably already know this, but there are a few things you’ll need to empty your RV’s holding tanks:

  • Disposable gloves. We like the double-glove method: A pair of tight-fitting latex gloves and then longer, thicker rubber gloves.
  • Black tank backflush hose. Use a dedicated garden-type hose to connect site water to your rig to use in your black tank flush system.
  • Short piece of clear sewer pipe (with fittings on both ends). Whether an elbow or straight piece, this will help you monitor what’s coming out and when your tanks are empty.
  • Sewer hose with extension (if needed). This is what you connect to your RV. The other end goes into your site’s — or the dump station’s – hole to the sewer. A 90 degree bayonet adapter at the end is a good idea, of course.
  • Sewer hose ramp. That’s that articulated, plastic thing that makes a high ramp (at your RV) down to the sewer hole in the ground (which should be lower than your RV).
  • Flush King or other back flush valve. Your RV’s onboard flush system is only so good. This is the best way to get your tanks clean.
  • Hand Sanitizer. Whether it’s one of the evaporating alcohol-based ones or some good hand cleaner and clean water, you’ll want to finish up with this.

Storing your hoses, etc.
Keep your hoses, especially, in an enclosed, segregated bin or other storage container. We like to keep the hose, sewer attachments, etc. in a plastic garbage bag (that we change frequently) within a bin for further safety. Keeping your hoses and connectors away from other RV tools — especially your fresh water hose — is absolutely critical.

You should sanitize all of these tools in a solution of bleach and water (1/4 cup to a gallon of water) frequently to sanitize them. Also frequently inspect your sewer hose for holes, cracks and breaks that can lead to a mess later. Sewer hoses have an active life of about 2 to 4 years before they start becoming brittle.

When to dump
You’ll want to dump your tanks when they are 3/4 or more full. If you need to dump sooner — perhaps you’re moving to another site or going home — be sure to fill BOTH tanks with fresh, clean water until they are as full as possible. Dumping your tanks when they are less than 3/4ths full will not allow enough down pressure in the fluids in the tank to properly clean them. Keeping enough water in your tanks will help to prevent drainage problems later. If you’re at a site with full hook-ups, keep a few gallons in each tank from the start — a process called “priming” the tanks.

Some RVers keep their gray tank valve open. This is not an ideal set-up. A slow trickle of gray water will allow solids to stay in the tank, hose, etc. and can contribute to problems later as well as smells as food particles and other debris starts to break down.

The process
When it’s ready to dump, take things slowly and in order. Doing so will keep you safe and avoid problems now – and later.

  1. Get suited up. That means gloves, protective eyewear, and even some old rags in case you need them. We like to keep a three gallon bucket at the ready in case we need to catch small spills or have something fittings can drop into.
  2. Connect everything. Keeping your tank valves closed, connect the clear sewer pipe to your RV’s tank outlet pipe, then the Flush King backlash valve, then the sewer hose, the 90 degree bayonet fitting at the end, and then, finally, to the sewer dump hole in the ground. Check the fittings to make sure they are tight. You may need to place a large stone or something else heavy over the bayonet fitting into the ground to keep everything draining into the RV park’s sewer system.
  3. Keep it moving downhill. Use your sewer hose ramp to create a downward flow for anything moving through the sewer hose to the hold in the ground.
  4. Double check. Make double sure that all of the connections are tight on your RV’s tank valves and the sewer hose. Trust us here; a loose fitting can cause a messy, panic-filled situation later.
  5. Get that black flush going. Make sure your black tank back flush system is hooked up. Start pushing water through that system by turning on the water supply. Then, quickly….
  6. Pull those gate valves. Starting with your black tank gate valve, give the pull and steady, smooth pull. Listen as the waste evacuates the tank. Watch through the see-through piece of sewer hose you installed to make sure waste is flowing out easily and quickly. If you filled your tank full (or nearly so), you see waste moving fast and a big blast of water as the tank empties itself. Once the black tank is completely empty, turn off your black tank’s flush system (allow for any final liquid to come out), close that gate valve and then pull the gray one. Keep an eye on what comes out. Wait for that tank to empty too.
  7. A final rinse. Close both tank valves and wait for everything to drain out. Make sure a spare garden hose is connected to your water supply and the Flush King (or similar brand) back flush valve. Now you are going to get your tanks clean! Slowly open your RV’s black tank pull. Wait for anything else to drain out. Then, CLOSE the valve on the Flush King back flush valve, on the side that does into the hole in the ground. Turn “on” the water supply to the Flush King back flush valve, allowing the fresh water from the garden hose to rush up into your black tank. Have someone inside the RV hold open the toilet valve and watch/listen until they see/hear water starting to come up to the top of the tank (some RV waste systems allow you to look down into the toilet when held open to see the holding tank itself). When the black holding tank is full, turn off the water to the Flush King back flush valve and open that valve your closed (that will allow water to drain out into the RV park’s sewer system).
  8. Rinse and repeat. Watch what comes out of your black tank after this back flush with the Flush King back flush valve. You’ll probably see lots of waste and toilet paper. And you thought your tank was clean! Perform this process on your black tank again (put to two or three more times), until the water coming out is relatively clean. Close the black tank pull, open the gray holding tank pull and do the same there. This tank may only require one or two back flushes.

That’s it! Pretty easy, right? Be sure to rinse out everything with fresh, clean water when done (if putting away). Be sure to keep those tank valves closed once you are done and, if you’re staying at your site, fill each tank with about 2 to 3 gallons of fresh, clean water to “prime” them again and get a good base of clean water in each tank.