RV Holding Tank Dumping 1-2-3

TheRVgeeks Plumbing, Water & Sewer 22 Comments

Dumping your RV’s black and gray tanks might seem like a no-brainer, but we can’t tell you how many times we’ve seen people who could use a little help with the basics. Properly dumping your RV’s holding tanks requires a few simple procedures to help keep things odor-free and running smoothly.

For everyday tank dumping, this video is the “express version” of our original “How To Dump & Clean an RV Black Tank.” If your black tank really needs a super cleaning, you can watch the original, more detailed video here:

How To Dump & Clean an RV Black Tank

If you’re not having tank odor problems and just want a quick overview of basic tank dumping procedures, this new video gets right to the point.

Many RVers seem to think their black tank is clean when they just empty it and flush out the sewer hose with water from the gray tank. Even those RVers who use a black tank flush system often don’t utilize the most important piece of equipment necessary for monitoring the cleanliness of the tank: a clear sewer elbow.

But using a clear sewer elbow on your camper isn’t enough. As we demonstrate, even a black tank flush connection still won’t do the job unless used correctly. We’ll show you how to be sure your black tank is really empty, keeping it clean & odor-free and making your motorhome, travel trailer or fifth wheel a nicer place to be.


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We're handy RVers, not professional technicians. We're happy with the techniques and products we use, but be sure to confirm that all methods and materials you use are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

We sometimes receive products for evaluation at no cost, and The RVgeeks are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. But our opinions are our own, you won’t pay an extra penny, and we only link to products we personally use, love and can recommend to friends with complete confidence.


Comments 22

  1. Hello! I’m about to try Happy Campers Extreme on my black tank. (Kind of excited actually). Does anyone know how long it can sit in there without harming the tank? We will be gone for a little over 24 hours this weekend and thought this would be the perfect time to treat the tank, but I don’t want to harm it… ~ Katie

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      Hi Katie! There’s no reason that you can’t keep happy campers extreme in the tank as long as you want to, and actually the longer it’s in there, the better it will work. That said, of course, follow the manufacturers instructions

  2. I have a 2017 Montana fifth wheel that the black tank empties very very slow. I am considering checking the vent pipe to ensure it is not clogged but having three vent pipes on my roof, I’m not sure which is the black tank vent. Any suggestions would be greatly appreciated.

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      Hi Ron,

      Sorry to hear you’re having trouble! There’s a couple of ways you should be able to go about identifying which vent pipe is for the black tank… some more desirable than others! ;)

      1. You can do the “nose” test… and just get up on the roof and take a whiff from each one. While the gray tank won’t smell like roses, either, you should easily be able to tell the difference between them.
      2. You can do the “ear” test… have a helper open the toilet and pour water into the black tank, slowly (it helps if there’s already some water in the tank) while you listen at the vent pipes on the roof. When you hear the sound of water pouring in, you’ve found your pipe.
      3. We’ve heard of people removing their vent caps and using a hose to put water into the tank from the roof. By checking to see which tank begins to fill up using their monitor panel, they know which tank that vent is for. On the plus side, this technique can also help to clear anything in the pipe that may be causing the lack of air flow… but if there IS a blockage, this could also end up having water pour out somewhere it shouldn’t. We wouldn’t want to rely on the vent pipes being water tight… since they weren’t designed to be.

      There’s a couple of things to consider:

      • Depending upon the layout of your tanks, one tank could have more than one vent pipe to the roof. As an example, our black tank is “U” shaped… and is installed so that the upper legs of the “U” extends up around the chassis rails. As a result, there are two vents for it, one on each side coming out of the top of each leg of the “U”. This ensures that if the tank fills up to the point that there’s isn’t a path for air across the top of the tank between the upward facing leg sections, each side still vents.
      • It’s possible (and not unheard of) that what’s causing your problem is a piece of the tank wall itself. When they make the tank, they cut the holes in it for all of the plumbing connections… and, sometimes, those pieces are left inside the tank. When that happens, they can end up finding their way to the drain pipe and clog it. We hope that’s not your problem, as it’s quite difficult to get that removed… and it’s quite a messy/smelly job since the tank doesn’t drain properly with that in the way.
      • You may want to try doing a soak with a heavy-duty waste digestor (like Happy Campers Extreme or NoFlex Waste Digestor) to see if the blockage is organic. Fill the tank with fresh water and a healthy dose of either of those two products and let it soak for a couple of days, then see how it drains. If nothing else, it should help to clear out any organic matter/tissue that’s clumped up around a possible disk of plastic from the tank wall, allowing it to drain better so it won’t be so messy getting out that piece.

      Hope all of this helps… and let us know how you make out!

  3. I am set up with a plumbed sewer line to a septic that others on the property are also using. My issue is while I opened the blank tank (after opening the grey tank and hearing the water empty) the black tank also sounded like it emptied into the same sewer line (septic). The light indicator shows the blank tank is still at about 75 % full. My question is how to I empty the black tank? I can’t see what else I can do?
    I must be doing something wrong otherwise it would empty on it’s own wouldn’t it?

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      Hi Nancy! There are a couple of possibilities here. The first thing to determine is if the indicator is showing 3/4 full due to a sensor malfunction rather than it actually being that full. Even though you’re connected to a permanent sewer line, gravity should be doing the job of draining the black tank. It sounds as though you’re not making the (serious) mistake of just leaving the black valve open, so pyramiding (liquids running out and leaving solids behind in a pile) shouldn’t be the issue. You should be able to tell if the tank is really 3/4 full by seeing if you have very little capacity after dumping. If only a day or two goes by and your tank shows full, it was indeed likely 3/4 full, as indicated. If you can use the tank showing 3/4 full for a considerable time without it going to a full indication, it’s likely just a sensor issue (showing 3/4 when it’s really not). That would best be dealt with by doing a good tank cleaning with a product like Happy Campers Extreme Clean: http://amzn.to/2EeKk8a

  4. We are new to RVing and bought a 2016 Forest River Sunseeker 23 footer. We used it for a week after moving from MA to NC. I “emptied” the black tank, but after seeing this video I realize I did only a third of the job! We were then caught in a money pinch and the RV was only used occasionally as transport. My question is, how long can waste sit in the black tank? It has been a year.

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      Hi Don. If you left your tank sitting for a year without having thoroughly cleaned it out first, the best thing to do is give it a real blast of a cleaning with a product like Happy Campers Extreme Tank Cleaner, available here: http://amzn.to/2dS80Rh on Amazon. We have not personally used this product ourselves, but have read and heard very good things about it. We’d follow the instructions and soak the tank good for a while. We use the regular Happy Campers ( http://amzn.to/2dS9hYB ) and are very happy with it. Please let us know how you make out. Hope this helps.

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  5. Hi RvGeeks! I a question. First let me say thanks I enjoyed the video. I have nothing but problems with cleaning the black water tank now my first question is….you said if you are camping somewhere that only has a dump station not to dumb the black water tank there. How long can we go without dumping? A little info on our rig we have a 2007 Jayco 31 ft travel trailer.

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      Hi Kimberly! When it comes to dumping the black tank, it’s not that you CAN’T dump it at a dump station… we just prefer to avoid it whenever possible, since taking the time to flush the tank out can often be a problem for two reasons: 1) There may be a line-up of people behind you waiting, and 2) there might not be a hose fitting on the water line at the dump, which prevents us from connecting it to our black tank flush fitting.

      How long you can go without dumping depends on a lot of factors, with the capacity of the black tank being an obvious one. Whenever we’re dry camping, we always try to make use of the facilities at a campground, which keeps the “load” (sorry lol) off our black tank. Of course if we’re boondocking, there may not be any other facilities to use. We often go for 2 or 3 weeks or even more without dumping our black tank, but that’s because we have a pretty good size tank (45 gallons) and because we really make the effort to use other facilities when available (a vault toilet at a national forest campground is fine with us).

      So what we do, when we can, is try to have at least one night at a full-hook-up campground every couple of weeks (or however often we need to dump), rather than dry camp for very long periods with a single break of even one night. We can dry camp for two weeks, dump our black tank during a 1- or 2-night stay at a full hook-up campground, and then head back out for another 2 weeks or more without dumping black water.

      Of course if your tank is full, and you’re in the boonies, and you don’t have a full hook-up RV park available, dumping black at a dump station isn’t the end of the world. People do it all the time. Although that’s probably why so many people have tank odor problems…. they regularly dump their black tank without properly flushing it out. Just minimize that if you can.

      1. Thanks for the super fast reply!!!! I completely understand why dumping at a dump station is not the best idea. We just left from a weekend of camping and it took me about an hour to clean & flush the blank tank. To get the bigger picture it’s 3 women in the RV and we try our best to not put septic safe toilet paper in the toilet but we occasionally forget. Anyway we are going camping on Labor Day weekend to a place that doesn’t have sewer hook ups. They do have bathrooms there so during the day I will be using those and we don’t fill our tank up that quick. But we won’t be going camping again tip the end of October. The October trip will be to a place that has full hook ups. But can we wait that long to dump the blank tank?

        Also is there anything you can suggest so that it doesn’t take me so long to clean the tank? We have the clear elbow so that I can see what’s coming out. We always put the green stuff in the tank so that it break down the waste. We used to have a clear elbow with a hydroflush attached, now we purchased a Flush King which I just used this weekend for the first time. Now I will say I was only putting water in the tank for 2-2.5 minutes and after watching your video I think I maybe need to put it in longer and watch to see how full the tank is. What is taking me so long is that I’m not able to get it clean, it’s empty, but every time I add water into the tank it’s still coming out with dirty water, or clear water but that still has some small “particles” in it lol.

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      Are you an RVer Terry? If so, I doubt you would ever refer to a clear sewer elbow as “bogus” just because someone who thinks he’s replicated an actual black tank comes to some incorrect conclusions. Some of what he says is accurate (the flush systems that spray up through the drain pipe are indeed useless). But a clear elbow is one of the most important pieces of equipment an RVer can own. Nobody claimed that it will guarantee that your tank is 100% clean, but it will allow you to avoid leaving easily identifiable debris in the tank.

      Unlike the clear tank in the video, ours has the drain pipe on the bottom, not the the side, and also contains multiple built-in flush nozzles. Both of these differences give us an advantage, along with the thousands of other RVers with similar setups. Our tank comes completely clean. We know this because the real world test is keeping your tanks and RV odor-free over the long haul. We’ve been full-timing for nearly 12 years, and our current RV, nearly 10 years old now, has zero odor once dumped. Ever. If we left debris in the tank after every flushing, the tank would eventually reek after all these years. Apparently we’re doing something right. But we couldn’t do it without the clear elbow.

      Here’s a video we made that shows how to more thoroughly clean a problem black tank: http://www.thervgeeks.com/maintenance/dumping-cleaning-an-rv-black-tank/.

      Before you bring up the fact that the same guy recently published a video claiming that ice in the tank is useless too, that is also not the case. Ice works great, but not for the problem that he was trying to solve. It won’t fix pyramiding, but therefore coming to the conclusion that it does nothing is incorrect.

      Thanks for visiting our website. I hope you find some of our videos useful for you if you own an RV.

      1. “Are you an RVer Terry?” Yes, I’ve done about 26,000 miles in the past two years. I don’t have a flush valve or a clear discharge pipe and I’ve never had an odor or a blockage. Nothing else really matters.

        Since you brought it up, exactly what DOES the ice do? You didn’t indicate anything.

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          The mechanical action of ice vibrating and moving over the bottom of the tank as it melts helps loosen any stuck-on material. If you watched the ice video using the clear tank, you’ll notice that the ice only nibbled around the edge of the “pile” but completely cleaned the bottom of the tank where the build-up was simply a thin layer.

          Our real-world use of ice to help clean the bottom of a black tank was very successful. And the way we knew that it worked? The scrubbed-off debris was visible coming out through the clear elbow after nothing but clear water had come out during multiple soakings and flushings. ;-)

          I apologize if my response came off as terse. We truly appreciate all input, comments, experiences and expertise that people add to the conversation. A healthy exchange of ideas is a good thing all the way around!

  6. the plumbing in my gooseneck is really simple. i have the two holding tanks under my trailer and that is that. And since i camp alone in my gn, with other campers tho, its only me at the dump station. When I saw the clear elbow i went to amazon to get it, i found this too. the one girl solution at the dump station. http://www.amazon.com/Valterra-F02-4100-45%C2%B0-RV-Hydroflush/dp/B0002UHVAA/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1402946153&sr=1-1-catcorr&keywords=clear+rv+sewer+adapter yinz may have to cut and paste. you flush directly from the elbow. Right now tho, I am in the process of tearing out my two roman shades (literally) to fix them. enjoyed that video. your stuff has been so helpful to me the post really primitive camper.

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