Are you dumping your black tank correctly?


by Doug Swarts, Drain Master, Inc.

Oh no!

Although dumping RV waste is a relatively simple process, it’s important to use both the proper equipment and procedure that ensures you will not cause a spill or get the contents on you or your clothes.

The “Old School” or industry standard method has worked for more than 50 years and while it gets the job done, some RVers are still apprehensive about the job. I say job because most people consider this task a job. It needs close attention before, during, and after the job is complete.


• Always put on a pair of disposable gloves before handling any parts of the sewage system.

• Inspect the hose for any worn areas, splits or openings.

• Then check the fitting ends to ensure they are secure and will not drip.

• Check the ground sewer inlet to make sure the opening is compatible with your fitting.

• Finally, check your sewer outlet to ensure the cap is still in place, as it was the last thing you installed after the last dump job.


• First install the sewer inlet fitting (on the hose) into the sewer inlet in the ground, making sure it is secure.

• Next, take the other end of the hose and walk it to the RV sewer outlet. While holding the hose fitting under the sewer outlet cap, slowly remove the cap making sure any drips go into the sewer hose fitting.

• Connect the hose fitting and double check to ensure it is secure and tight.

• Check that the hose is lined up with the ground inlet and nothing will stop the flow when it starts. Check again.

• Open the gray valve first and allow a couple of gallons to flow to the sewer. Close the gray valve and check for any drips or leaks. Make any corrections, if needed.

• Then open the black valve and let the contents evacuate.

• When the flow has stopped, close the black valve and then open the gray valve again to rinse the sewer hose. When empty, close the gray valve.

Rinsing (flushing) the inside of the holding tanks is a good thing but it’s not necessary to do it every time you empty the tanks. I would suggest every third time you dump but that is entirely up to you. It simply can’t be done too often but should never be done when dumping at a designated dump station with other RVers waiting in line. As a courtesy, always wash down the area around the ground sewer inlet;  those waiting to dump their tanks behind you will appreciate it.


• Check to see that the sewer hose is empty and that the tank valves are fully closed.

• Then slowly remove the hose fitting, allowing any drips to fall into the hose.

• Replace the cap on the sewer outlet as well as on the hose (if equipped), then walk the hose back to the sewer inlet, holding it higher than the inlet, allowing any residual water in the hose to flow into the sewer.

• Remove the hose fitting from the sewer inlet and cap it, if you have one, and cap the sewer inlet.

• Return the hose to its storage location, and inspect the area to ensure all is ready for the next site occupant. Finished!:

Doug welcomes your waste management questions! Send them to: Deanna (at)

Doug Swarts is a 25-year RV industry expert at creating and implementing revolutionary products for all RV waste management systems. His sound principles of RV waste management have led to a group of products designed to make the unpleasant task of dumping holding tanks more sanitary, safer, and convenient for the user. Doug is the founder of Drain Master Inc., of Hollister, CA, which sells, as well as installs, Drain Master, Waste Master, 360 Siphon, HepvO, and other RV waste-related products. Got a question about your system, call the friendly folks at Drain Master 877 787- 8833 toll free.


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Dan H

I would add a step before removing the cap from the sewer outlet: “Make sure all tank valves are closed.” I have two grey tanks and open both grey tank drain valves so the tanks equalize (the kitchen grey tank fills much faster than the bathroom grey tank.) Of course, the black tank valve is closed. I once took the cap off and forgot to close the grey tank valves. There is a lot of pressure behind 50 gallons of grey water!

Dennis M

Had never thought about draining some gray water first. For 15 plus years I have always opened the black first and then the gray. Your suggestion gave me pause and it would be easy to do on our rig since we have two gray tanks. A few days after reading your article I was ready to dump and I opened the kitchen gray tank first as you suggested. Whoa, stand back, hose not connected properly, gray water pouring out! Just think what would have happened if I had not read your article! I’m a believer!


Can anyone explain to me how the black tank flush works. Is it a single hole at the end that floods the tank. Is it a pipe with holes in it that circles the tank and washes the walls. Is it a spinning pressure nozzle.
How does it work?
When I dump with unit level waste water runs slow. I’ve started to tilt the unit and I get more flow and what seems to be more material. I use a clear connection so I can see when its clean…

Mary Woods

The dealership told me they add a couple bags of ice to the water in the tanks then drive it around for a bit. He said the ice removes the buildup on the sensors and works better than specific sensor-cleaning chemicals. Not so sure I believed him but we’ll see!

Edward Owens

Running the grey water first for a few seconds was new to me and sounds like a good idea for checking connections. I have also adopted leaving the black tank valve open after it has emptied and running some grey water back into the pipes from the black tank. Have often freed more sludge this way. After opening and closing the grey tank valve a few (two or three) times I close the black valve and then let the grey dump away. Help keeping the pipes clean at least.


A clear fitting at connection is a great way to tell when the tank is empty and when clean when rinsing. I too added the extra gate valve as extra insurance so I do not get any surprises when I remove the cap.

Bob Lewis

I often see mentioning of wearing gloves during the dumping process, but, I cannot recall ever seeing mentioning of wearing protective eye and face wear. I purchased a full face shield from Harbor Freight for a few dollars and wear it when doing the dump process, especially pulling out and putting back the hoses in storage. Better to splatter the shield rather than the face or eyes.


I had a leaking black tank valve so I bought an external valve that simply twisted on where you attach your hose, then you attach your hose to the other end of the valve. It worked good as it stopped any leakage. Then this past weekend while camping, I went to attach my hose to the motorhome. While twisting the hose into place, I inadvertently turned the valve, releasing it from the motorhome. Yep, I had myself a “black shower”, and a mess! So guess what I just finished doing. One new black tank valve successfully installed. Anyone want to buy a “slightly” used external valve? 🙂

Eric Meslin

I used the Walmart gloves, but they kept ripping. Someone commented about medical gloves sold at Harbor Freight. Much better, but I still only use if a washroom isn’t available near the dump station, or if I don’t have time to wash up in the trailer. We take our time to flush and clean up only if we have a sewer hookup, or if there isn’t anyone approaching the dump station behind us. Otherwise, even after wearing gloves (and removing them correctly), I have hand sanitizer in the door of the tow vehicle. We live in Florida, and my hands tend to get very sweaty in the gloves.

We have a built-in black tank flusher. I only use it if we have time at the dump station and there’s a faucet I can use. It’s effectiveness is also in direct proportion to the water pressure. If there’s a pressure reducer installed, or it’s on well water, the flusher isn’t worth using. If someone is behind us I don’t use it either.

Wolfe Rose

As GettinBy commented, we all did fine before making dumping an elaborate process. I don’t know how many hundreds of times I’ve dumped now, but I do it without gloves, in 3-4 minutes, and have NEVER had reason to believe I got myself sick in my process. No CDC-5 gear needed! For a slightly comedic description of what I do, see here:

BTW: In my experience, ANY of the hose-pressure tank rinsers are gimmicks, about as effective as just flushing the toilet again while draining. I’ve pressure washed tanks right after running the built-in rinsers, and what comes out then would make you think they hadn’t even drained the tank yet.


Good article with tips I will use. I was surprised there was no mention of rinsing out the house before disconnecting from the sewer. I always rinse the hose with fresh water so I don’t store it with as much grey water in it.


I especially appreciate your comments about considerate use of black flush systems. As these systems have become essentially “standard” equipment, I find many RVer’s thoughtlessly keeping many waiting in line while they flush. It’s as if the “flushers” completely ignore how they feel about waiting in long lines. Or, maybe, they feel they are getting even by taking their time once they reach the head of the line. In any case, it wasn’t that long ago, before the pervasive spread of black flush systems, that RVer’s simply dumped tanks then moved out of the way – and we all (somehow!) survived.


If it’s been awhile since we’ve use our RV and the “black” side, depending on how far we are going to go camping I’ll get a bag of ice and add it to the “black” tank with the chemicals. While we are traveling the ice will melt, and with the motion of the camper it ice will dislodge the crusty stuff.