Warning: For those who don’t like poo talk I wouldn’t read this post. However, if you plan on living in an RV you probably better get used to it.

We realize this is a long post so if you just want to skip ahead click one of the following links to jump to Do’s and Don’ts or Diagnosing Odors.


If you currently live in an RV or are planning to, gone are the days of flushing away and easily forgetting about what you just did on the throne. You have entered a world where a person has to become much more involved with the results of all those bathroom trips. These are the days of doing it and then storing it, treating it, dumping it, rinsing it, seeing it and hopefully not smelling it. This is a learning process, one that isn’t always easy and mostly not fun unless it’s all working perfectly. In our experience it’s been less than perfect.

Prior to living full time in our RV we gathered as much information as we could regarding this topic. Between personal experience with our first RV (a pickup camper), friends/family with RVs and some helpful RV bloggers we knew the basics:

  • Number 1 and number 2 go in to a dirty nasty place called the “black tank” down in the depths of the RV.
  • It is unwise to put things in the black tank that don’t break down like feminine products or baby wipes. Kind of a given and also common rules for those with septic systems for their stick and brick homes.
  • It is recommended by some that a special RV toilette paper be used so that it breaks down properly in the tank.
  • You should put something in the tank to keep the odors from getting noxious and leaking in to your RV or knocking you on your booty when emptying the tank. There are many options and opinions on the subject.
  • You have to purposely add water back in to the bowl after you flush. A number 2 in an empty bowl makes for some potty painting that nobody wants to see, or clean up. In addition, always leaving some water in the bowl between flushes keeps the rubber seal from drying out.
  • The black tank is dumped using a hose or tube in to a hole in the ground specific for that use, not just any ole hole in the ground.
  • Crap rolls down hill. Make sure you’ve got a downward slope between your black tank and that hole in the ground.

Do’s and Don’ts?

We thought, Okay, we’ve got it. Keep some water in the bowl, don’t put anything weird in there but do throw in a treatment of some sort, hook up the tube to the hole in the ground when you want to dump it and make sure it’s downhill. In theory, all of the above should happen without a spill or a smell but, sometimes folks, shit happens. After owning an RV of some sort for about 3 years and living in one full time for about 6 months we’ve learned a lot more. We are far from experts and fully expect to learn a lot more on the topic over the years so please don’t take what we say as gospel – it’s just our experience and we hope it can help some of you. Some of what follows we learned the hard way, some from expert advice and some from our trusty RV bloggers who are always a wealth of hands on knowledge. That being said, here is a more comprehensive list of do’s/don’ts followed by where to look for that stubborn whiff of number 2 you keep smelling.

  • DON’T leave your tank totally empty after dumping it – always add water so that the bottom of the tank has an inch or so of water. Hard to tell since you can’t see it but we try for a couple gallons. Starting to use your tank when it’s totally dry can lead to a “poo pyramid” inside the tank that dries out and gets stuck there.
  • DON’T dump your black tank every time you take your RV out for a weekend. This is a gravity system and requires a bit of force to empty properly. A tank that is only a fraction full will only trickle empty and leave a lot of solids in the tank that build up over time and the noxious gasses in your tank will just get worse and worse. We learned this one the hard way in our pickup camper.
  • DON’T leave your black or gray tank valves open all the time when at an RV park. This is effectively combining the first two don’ts for the black tank. In this scenario all the liquids will drain out leaving you with a dry tank and a “poo pyramid” situation. Go ahead and leave the hose hooked up but wait until the tank is nearly full, or fill it with fresh water, before opening the valve. It also allows the gasses from the holding tank in the ground to vent back up, through your tank, and out the vent in your RV. Your neighbors would prefer you don’t do that. Some people like to leave the gray valve open but put a P-trap in the hose. Refer to the last section for what a P-trap does.
  • DO dump your gray tank (for water drained from sinks and shower) after you dump the black tank. This water is gross in itself but nothing is as gross as poo. The gray water running through the sewer hose will nicely clean out any remnants left from dumping the black tank. (This assumes your black and gray tank converge in to one pipe.
  • DO use plenty of water when flushing. Yes, you may have to dump more often but not using enough can also result in the “poo-pyramid” mentioned above. There can especially be a problem with a bunch of men that do number 1 outside and only number 2 inside or with a bunch of women since we use toilet paper for both number 1 and 2. If you are worried about your water footprint keep in mind that you will still be using way less water than a household toilet.
  • DO use a toilet paper that breaks down. It doesn’t necessarily have to be RV specific toilette paper. Many people buy brands that say septic approved on the label. If you’re unsure about your TP put a couple squares in a plastic container full of water, put on the lid and shake. If it doesn’t start to break apart in a few seconds it’s probably not a great one to fill your black tank up with. In fact, if you get carried away with the wrong TP you can actually create a clog between the tank/vent and the toilet flap. Surprise! Then when you flush all those fumes poof up in to your face. This is sometimes called a “Black Tank Burp”, but in reality the burp is happening between the clog and the toilet. Not cool.
  • DON’T, not matter how desperate you are, stick anything down in to the tank that isn’t intended to be used for that. Case in point, let’s say you have clog as described in the bullet point above and decide to use a stick from a tree to unclog it. All fine and good until the stick breaks and you now have 3 feet of tree in your black tank. In case you’re wondering the stick did eventually come out – we were lucky.
  • DO make sure you are securely connected to the hole in the ground by what ever means necessary, even if it’s a foot or a rock, when dumping. Also make damn sure all fittings are tightly connected. There’s a lot of force flying out of that tank when you open it up and things can blow apart, all over the ground and most likely on you….Yes, this happened and I don’t want to talk about it.
  • DON’T rely on the dumping station to have fresh water for cleaning out your hose (or spills as described see above) after dumping. In freezing climates they may have winterized, leaving you to clean up your blue-chem bio hazard spill with left over soda from the weekend.
  • DO have a clear connector somewhere in the line when dumping so you can see, although it’s gross, how things are moving along.
  • DO always have a ready supply of disposable latex gloves in the compartment where your black tank release valve is. The sight and smell of poo is disgusting; having poo actually touch your skin is a life altering experience which may require years in therapy.
  • DO use the fresh water flush out valve, or buy a fitting with one built in. After the initial dump you can even close the valve for a while to let the water accumulate and better guide what is left to the dump valve. We will sometimes do this multiple times and you’d be surprised what comes out even after you think it’s all clean.
  • DO use some kind of black tank treatment (and gray too if desired). There’s tons of debate here. Some prefer a strong chemical approach to control odors. Some prefer an environmentally safe enzyme approach. Others make a home made concoction of household products. We’re currently using an enzyme approach, feeling that we really want to make sure the TP breaks down. For now all we can say is use what ever works for you, your wallet and your conscience. If anyone is interested – here is a recipe for a home made version that some friends swear by: 1 C. Baking soda, 1 C. Downy, 1 C. Ammonia (lemon), 2 C. Pin-Sol (lemon). Shake well and put a couple cups in the tank after dumping.
  • DON’T trust those level indicators. Not only can they fail but “stuff” can get stuck on the sensor and give you a bogus reading. The indicators for both tanks in our RV for instance never go below 1/3 (sometimes 2/3) despite dumping and blasting with the fresh water flush until nothing but clear water runs out and then letting it run dry. There are tank sensor treatments that you can use, per manufacturer instructions, to try to get them working more reliably but it’s still questionable. If ours reach “full” we know it’s true because you can actually see what’s inside the black tank when flushing or we’ll get a really stinky burb out of a sink drain if the gray fills up.

Diagnosing Odors?

Even if you follow all the tips above (and I’m sure there are others out there) you may still have odor problems. Things break and you have no idea how well (or poorly) the previous owner of your RV maintained the tank. One thing we’ve learned for certain is that odors are difficult to track down! If you find your RV sometimes, or all the time, smelling like a trail head vault toilet then something is probably wrong. Tracking that something down can be difficult. We’ve battled this issue in our current RV (a 2002 that we purchased about 1 year ago). Through the same resources we mentioned before we learned to look at the following for culprits:

  • VENT TUBE: There is a vent tube on your roof somewhere that vents the black tank. There should be one for the gray too and it sometimes smells worse. This vent can get blocked by a variety of debris and may need to be cleaned out. If this happens those gasses just build up and come out when you flush or any other crack it can find. It can also be venting just fine and thanks to the right breeze, be wafting right back in through an open window. It is commonly suggested to get a 360 vent that twirls around in the wind, hopefully blowing the smell off away from your RV.
  • TOILETT SEAL: That black rubber seal at the bottom of your toilet can get dry and cracked over time allowing the water to seep down in to the black tank and reveal a not-so-air tight seal which can allow odors to come up from the tank. This issues is normally evident by the fact that the toilet is always empty when you go to use it even though you added water after you last flushed. If your toilet holds water for days your seal is most likely fine.
  • P-TRAP: For those unfamiliar with a P-trap it is a u-shaped portion of pipe in plumbing drains that traps a small amount of water when not in use. This water prevents odors from traveling past it back in to your RV (or house). Some RV toilets have an overflow tube in case the flush valve gets stuck open and over flows the toilet. This tube has a P-trap and if the water in it dries up the odors can leak back up. You can fill your toilet up to the point that water goes down the over flow tube to make sure you have water in the P-trap.
  • EXHAUST FAN: Yes, those fantastic fans are fantastic! But if you’ve got it running above or very near your toilet while flushing you are sucking all those gases right up in to your RV.
  • OPEN WINDOW: No matter what you do when you’re dumping you will get some smell outside. If you’ve got a window it could be wafting right inside your RV.
  • BLACK TANK GONE WRONG: If you or the previous owner haven’t been maintaining things properly (leave the tank dry, allow poo pyramid build up, don’t use a treatment, flush feminine products) you can have such a black tank atom-bomb build up that you nearly can’t prevent odors. In most cases, if everything else is working right, this should only be perceptible while dumping but if it’s really bad it probably can’t be prevented. A method we’ve been told to try and remedy this is to fill an “empty” tank with fresh water to about 3/4 full, then add bags of ice and drive around for a while. The ice is supposed to knock any cling-ons off the sides of the tank so they can be flushed out.
  • BREAKS in plumbing lines: Any breakage that creates a non-air tight seal between the black tank and the interior of your RV can lead to odors. We found this to be the case in our RV, well the repair man found it to be more accurate. The large plastic tube between the toilet bowl and the tank tube (inside the casing of our toilet) had a small crack in it. Only a tiny amount of water leaked through it during the flushing process – never enough to show on the floor – so we had no idea that anything was broken other than a very slight rocking feeling of the toilet, and I mean very slight. This crack was between the rubber seal we mentioned before and the black tank but was on the interior of the RV, allowing small amounts of odor to leak back in to the RV, especially when our fantastic fan in the hallway was running. It turns out we had to replace the entire toilet, but man did that make a difference!

That is the length of our knowledge on the subject of black tanks, gray tanks, toilets and what lies between. As we said before, we are NOT experts. This is just what we’ve learned along the way but wish we knew at the beginning. Some of it can be debated I’m sure, and I bet we’ve got a lot more to learn. What we hope is that this post can help some of you out there that are asking yourselves – where is that smell coming from?


2 thoughts on “WHAT’S THAT SMELL?

  1. Believe it or not, your “Poo Posting” was very informative!!!!haha.  We got a travel trailer last month so everything is new to us.  I printed out your informative tips and we will carry them in our home away from home.  Take care.  So glad to hear Meg and pet are in good health.

    • I’m so glad it could help! We posted it to an RV group on Facebook and got some additional tips. First, if your black and gray tanks converge in to 1 dump outlet, never have both black and gray valves open at the same time. If you do, turds can get sucked up in to your gray tank (yuck). Just do the black first, close it, then do the gray. Also, there are things called vacuum breakers for the gray tank. There should be one under each sink. It just looks like a cap on the pipe but has a valve in it to “burp” excess pressure if it builds up. If these wear out the smell from the gray tank can leak in to the RV. Here’s a link: http://www.adventure.1tree.net/…/sewer-odors-in-your-rv.
      Congratulations on getting a trailer! Hope you have lots of fun in it! We’ve learned quite a few things but are by no means experts. If you run in to something weird though give us a jingle or email (green.carrie@outlook.com) and maybe we can help. Good to hear from you!

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