Tuesday, September 26, 2023


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) rvtravel.com.

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.



  1. 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!

  2. 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!

  3. 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…

  4. 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!

    • Hi Mary,
      Interesting, a dealer that RVs and passes along his personal experience to other RVers. Many tests including our own a number of years ago disputes the dealers findings, BUT if it works for him and you believe it works after your own scientific testing we would all like to know more about the perimeters you use, I.E. holding tank size, (ours was 60 gal.) outside temperature, (75F) how much water was added to the tank at what temp, (5 gal 65 F) how many ice cubes, size freeze temp and for how long prior to adding to the holding tank etc. (32 ice cubes, or 2 trays, approximate size 1.5/8″ 1 1./4″ by
      1 1/4″ deep tapered freeze temp 5 degrees for 2 weeks)
      We dumped the Black tank and flushed it until the water ran clear, then waited 25 minutes until we were sure no water in the tank. Outside temp 75 degrees from a low overnight of 50 degrees. Added the 5 gal. water, then the 2 trays of ice and went for a 5 mile drive on a 2 lane road where we could turn the coach back and forth, in and out of driveways along the way and over a couple of rail crossings before returning to our start point. Dumped the Black tank into 2 5 gal buckets.
      Conclusion; The water was very close to being as clean as it was when we put it in the tank. My coach had See Level tank sensors so could not verify if they worked better. The sensors are external on the tank. With the water clean our belief is the ice cubes did not help clean the sidewalls of the tank and therefore is ineffective. One well done video a few years ago did the test using a plexiglass tank in the back of a pick up truck and their conclusion was the same as ours.
      If you use plenty of water in your Black tank the chances of having issues are minimized.
      Hope this lengthy response helps, if you would like to talk to us contact Drain Master 877 787 8833 Toll free, we are here to help RVers have fun RVing.

      • 2 trays of ice? How about doing the test again with 10 lbs. of ice and a 1/3 tank of water. But of course you are selling something so you’ll probably not want to do any further testing that might prove your product to be a waste of money.

        • Carl, other tests have proven that bouncing ice in the blank tank does not work. Doug is correct. Do not accuse him of being biased because he is “selling something.” You don’t know that. I suspect Doug, being in the waste management business for decades and being considered a national expert on the subject, is fully qualified to answer without you tossing in an off-the-cuff accusation to try to discredit him. — Chuck

  5. 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.

    • Running the Gray back into the Black tank may not work on all coaches because of the way they are plumbed but it doesn’t hurt anything to do so. I found keeping the process as simple as possible works best for me. Someone mentioned something I forgot to add in an earlier post about dumping and flushing. When you finish the process it is a good idea to add a few 3 to 5 gallons depending on the size of your holding tanks to you Black tank. The water in the bottom will prevent solids from sticking to the bottom of the tank and keeps things moving around as you travel.
      Remember if you have questions regarding dumping holding tanks or related subjects you can contact us at Drain Master Inc. http://www.drainmaster.com or call our toll free number 877 787 8833.

  6. 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.

  7. 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.

    • One cannot be too cautious when dumping human waste Bob and a facemask sure insures you will have your eyesight at the end of the process. Uor system is totally enclosed so you never come in contact with what is inside, You can check how we do this here https://drainmaster.com/rv/sewer-hoses-and-storage We designed our system to be as simple and as safew as putting gas in your car! No Hazmat needed only rubber gloves IF you are putting Deisel in your vehicle. Go to http://www.drainmaster.com or give us a call 877 787 8833 toll free we love talking with customers.

  8. 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? 🙂

    • Dave,
      We all have tried a “quick fix” and in my experience they usually come back to bite me. Bayonet fittings have been used in the RV industry, (no other industry uses them) since the first holding tank was used in an RV 50 plus years ago. The proper fitting is called a Cam Loc compression fitting. They are used in almost all industries that off load liquids. Why, because they work and do not fail!
      Food for thought!
      If the system in your RV was set up similar to a gas pump, the hose is already connected to the pump (holding tank) and it has a nozzle on the other end with a shut off. When dumping your tanks, pull the nozzle out of the compartment, insert it in the ground sewer inlet, Open the nozzle valve, then dump your Black first, then your Gray. When done close the nozzle lever, pick it out of the ground sewer inlet and put it back in your RV. Thanks for asking Dave, but no on the used valve! 🙂 –Doug Swarts

    • To assure that it never happens again put a self topping screw next to one of the lugs on the twist off valve. It can easily be removed if you ever need to remove the the valve.

  9. 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.

    • Eric,
      I found the Harbor Freight 5 mil gloves are very strong and work well for a number of things other than dumping.
      The Black water flush is at best mediocre at cleaning the tank, it is however an easy way to fill the tank 2/3rds with water prior to opening the dump valve. Its the water action inside the tank while the water exists that pulls out the unwanted particulate in the tank. You could if you have a window in the bathroom put the hose through the window into the toilet and be just as effective, AND faster, BUT messier! Remember, if you use the Black flush buy a mechanical water timer and install it on the inlet of the flush system, set the time and it will shut off when it times out. Could save you thousands of dollars if for some reason you forgot you were doing this job as it will flood your RV. –Doug Swarts

  10. 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.

    • 40 years as a school custodian and I always use rubber gloves. I too have NEVER been out sick from a work related illness. I’m not looking to find out if gloves are the reason or nought. Please be safer than sorry. There are tons of diseases that are transmitted this way. We are always being cautioned of new diseases including skin eating disorders.

      • I seem to manage to dirty my hands after breaking camp and everything is put away. I keep a bottle of hand sanitizers & a rag in the door of my truck.

    • Spot on Wolfe, As I said to Eric the flusher is a more convenient way to fill the tank 2/3rds full before dumping.
      As for no gloves, I would have agreed totally, when I was in my 30s to 60s, ten feet tall and bullet proof but now in my early 70s being not sick is a gift each day. Rubber glove insurance for 5 cents is worth it to me. –Doug Swarts

  11. 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.

  12. 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.

  13. 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.

    • I have seen videos on ice cleaning demonstration and shows dumping ice down the toilet does very little, Although it can’t hurt. Ice floats so it can only touch areas where the water level is. There are several of these videos on Youtube.
      The best stuff I found is tanktechrx.

      • While I agree totally with Earl if it work for Tex it is doing no harm to the inside of the tank. Filling and dumping the tank is by far the best proven method of keeping the inside of holding tanks relatively clean inside.
        Also you cannot use too much water in your Black tank, you may have to dump more often but you will never have a plugged tank while will be your reward! –Doug Swarts


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