Your RV Black Water Tank: How it Works and How to Clean It

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If you’re an RV owner, and your camper is equipped with a toilet, then you know that dealing with the black water tank is one of the less glamorous aspects of the experience. But it’s important to understand how this system works and how to clean it properly so you can avoid nasty surprises down the road. In this blog post, we’ll explain how your RV’s black water tank operates and give some tips for keeping it clean and functioning properly.

RV Black Water Tank Hookups

What are the different water holding tanks on a camper?

Most RVs or Travel Trailers have 3 different tanks as part of the plumbing system:

  • A fresh water (or potable water) tank
  • a gray water tank
  • a black water tank

The tanks come in various sizes from 15 gallons to 40 gallons or more. Only a camper with a toilet will have a black water tank.

Freshwater Tank

The freshwater tank holds drinking water and supplies your sink, shower, toilet and faucet when a “city” water connection is not available at your campsite. The definition of potable water is water that is safe to drink. Pay careful attention at campgrounds, especially around the dump station. A hose with a sign marked NON-POTABLE water literally means water that is not safe to drink.

Do not connect it to your city water connection or use it to fill your fresh water tank. It is generally provided to rinse your hoses and equipment after dumping the dump. NEVER use non-potable water for anything that may come into contact with drinking water lines. Avoid using non-potable water for hand cleaning, as it’s safety is never guaranteed.

Gray Water Tank

When equipped, the gray water tank collects water from the sinks and shower(s) of your camper. The soaps and cleaners you utilize give the water a gray tint, hence the name gray water tank. This tank can be cleaned much like your black water tank, but because of the type of water in the system, it doesn’t usually require the amount of maintenance that the black water tank does. Some smaller campers may have a combination tank in which all used water is collected, black and gray. You can follow all the same protocols that you do for the black water tank when caring for a combination tank.

Black Water Tank

The black water tank is the collection tank in your RV is where all the wastewater from your toilet goes. This includes everything from urine to solid human waste and toilet paper. When you flush the toilet, the black water tank collects this waste and stores it until you’re ready to dump it. Depending on the size of your RV, you may have a small or large black water tank.

How Often Should You Clean Your Black Water Tank?

Most RV black water tanks have a capacity of around 40 gallons. That means that you’ll need to empty it every few days, depending on how much use your toilet gets.

A good rule of thumb is:

  • dump at least once a week
  • or dump when it is 2/3 full (or 3/4 or 75%, depending on your gauge type)
  • and dump at the end of your trip.

You do not want the contents sitting in the tank too long. If the human waste hardens and sticks to the tank bottom or sides you could be in for plumbing problems, odor issues or up to your elbows in your family waste when the system clogs up.  If you are a full-time RVer, you will need to empty your tank more often.

Also, make sure you empty your tank at the end of every camping trip and at the end of the camping season. This will help prevent the tank from freezing and cracking in cold weather, as well as prevent stinky surprises the next time you use your RV! After our last use for the season we perform a regular cleaning, then fill the tank with water and deodorizer and let it sit for a few days to soak. Then empty the tank completely for the winter.

What Supplies Do I Need to Flush the Black Water Tank?

When dumping the black water tank you will be working up close and personal with poo-filled sewer lines. With practice you can avoid coming into contact with any of the nasty contents of the tank, but even then there is always a chance you could run into a clog or have an equipment failure. It is always best to be prepared ahead of time.

The most common items you should have on hand are:

  • Disposable rubber gloves
  • Disinfectant spray/cleaner
  • Disinfectant wipes
  • Waterless hand soap and/or hand sanitizer
  • Sewer hoses with correct connections for your camper and the dump location
  • Sewer hose supports – Waste only flows downhill, sometimes you need to create that hill to get things flowing properly
  • Sewer adapters
  • Storage tote – a good sealing tote to keep all of your dirty stuff from touching your clean stuff.
  • RV Septic-approved toilet paper! It’s very important that you flush only waste and liquid down your RV toilet and into the tank. Use ONLY RV septic-approved toilet paper. Do not use flushable cleaning pods or flushable wipes in your black water tank. These products can cause clogs and other problems. Regular toilet paper can turn into rock hard clumps in the drain blocking up your system, damaging your level sensors and causing you to be up to your elbows in your family’s solid fecal waste in the middle of your trip. IT IS NOT WORTH IT! (I’m speaking from very unfortunate personal experience on this one.) Just buy the recommended TP for your system.

RV Toilet Paper

Where to Empty Your Black Water Tank

Your black water tank should be emptied regularly while you’re using your RV. When it’s time to dump, you’ll need to find an appropriate place to do so. This can be done at a dump station, a sewer-equipped site, or via Honey Wagon.

Full Hookup Site with Sewer Connection

Some campsites will come with a sewer connection at the site. These are called “Full Hookup Sites”. Full hookup generally means electric, water (city), and sewer connections at the site. It is important to locate the sewer connection before you park and level your RV at the campsite. There is no common location on the camper nor a common location on a campsite that sewer connections are located.

If your vehicle connection is at the rear and your site has a dump connection at the front, you could need 40′ or more of sewer hose to make the connection. Its a good idea to ask where the connection is on the site when booking to help prevent these really long runs of sewer hose.

RV Sewer Hose Supports

Campground Dump Station

Most campgrounds will have a dump station, even if they have full hookup sites. The dump station is a location that you drive (or tow) your RV to and dump the dump. There is usually a non-potable water connection to rinse your hoses or tanks. Again, be sure not to use this for any other use.

Dump stations tend to get very busy at checkout time, especially at campgrounds without full hookups at the sites. Bring your patience, wait your turn and be as quick as you can. If it’s your first time, try using the dump station at a less busy time to gain experience.

Knoebels RV Dump Station

Toter Tank (Portable RV Waste Tanks)

For sites that don’t have full hookup, and you are staying for an extended period of time, it’s a good idea to get a portable sewer tank, or toter tank. These come in many sizes. Be sure to get a quality one, with larger wheels and good ratings. You dump your RV’s tank into the toter tank via a short hose, then drag (by hand, with a bicycle, your tow vehicle or toad) to the dump station.

This prevents you from having to pack up your entire camper to move it to the dump station and then set it back up halfway through your stay. Remember, your hose from your camper to your toter tank likely won’t be the same as from your toter tank to the dump station, so don’t forget to bring that one with you, too.

Thetford Smart Totes RV Sewer

Honey Wagon pump out

Another way to empty your tank is to schedule Honey Wagon service with the campground, if offered. The staff makes rounds with a large towed tank or sewer truck to suck the waste out of your tank. Again, this generally needs to be scheduled ahead of time and usually incurs a separate fee over that of the site. Be sure to let them know if you have more than one connection point/set of tanks. Some larger RVs will have tanks at the front and rear, depending upon bathroom, sink and washing machine locations.

Honey Wagon Septic RV Service

Travel Plaza or Truck Stop Dump Stations

Dumping stations are usually located at campgrounds, RV parks, and truck stops. Love’s and Pilot Flying J’s have dump stations you can use while on the road for a small fee. These are good if you are trying to deep clean your tanks at home and are looking to for a place to dump.

You CAN dump your tanks at home, as long as it is dumped into a residential sewer system. It cannot be dumped on the ground, into a ditch or into the storm sewer. This is not an easy task for most homes, so best to empty the tanks before you leave the campground. You can also call a local septic service, or portable toilet (Porta Potty) company. They may be able to come to you and empty your tank for you for a fee.

How to Empty Your Black Water Tank

The first rule to successfully emptying your black water tank is to have water to empty. You want to ALWAYS leave your black and gray water tank valves CLOSED! You only open the valves when your tank needs to be emptied. If you leave the valves open, all of the liquid will slowly drain out leaving behind mountains of solid waste.

Once hardened, this solid waste WILL clog your plumbing system and will NOT be easy to clean up. We recommend running a few gallons of water into the tank at the beginning of each trip and adding an RV safe deodorizer solution. Do this again after each time you empty the tank to prevent issues down the road. Empty the tank when capacity reaches 2/3 (3/4 or 75%).

Here’s how to empty your black water tank:

  • Find a suitable dumping location.
  • Connect your RV’s black water tank to the sewer connection using a flexible hose. Make sure the hose is going downhill. Most dump stations have sloped concrete pads leading to the connection. Use sloping hose supports, if needed, to make the hose go downhill.
  • If you do not have about 2/3 of a tank of water, continue to flush the toilet until you do, if possible. The more water in the tank, the more efficient the dump action will be in sending all the solids out of the tank.
  • Open the valve on your black water tank to allow the waste to flow out. You can use a clear connector to visually see the progress or just listen for when the water flow slows.
  • If you have a tank flush connection, use that per manufacturer’s directions. If not, flush your toilet several times to rinse the tank completely.
  • Close the black water valve.
  • Open the gray water valve. This will rinse away any really dirty stuff left over from the black water.
  • Close the gray water valve.
  • Disconnect the hose from the sewer connection and your RV.
  • Rinse out the sewer hose with the non-potable hose. If using a fresh water hose to rinse, make sure you keep it clean and do not stick it down the sewer hose to rinse it.
  • In addition to cleaning the tank, you’ll also want to make sure that you keep the toilet inside clean. You can clean it easily with regular toilet cleaner. Check to be sure it’s suitable for RV use.

You may choose to use a flushable toilet wand, but throw the cleaning head away in the trash when you’re done. Do not put down the sewer connection!

Dump Station at Campground

How to Clean Your Black Water Tank

If you let your black water tank go too long without emptying it, you may need to do a deep cleaning. This is usually only necessary if the tank becomes clogged or if there is a bad odor coming from it.

Here’s how to deep clean your black water tank:

  • Start by flushing the tank with clean water to remove any waste that may be sitting in it.
  • If the toilet is clogged, you may need to manually unclog it. Plungers generally won’t help with this. We keep disposable drain clog tools in our camper. You may need to stick your hand way into the toilet to reach the clog. Again, our only clog was related to using non-RV toilet paper and I was down to my elbow in the toilet to get it unclogged on the side of the road on a 5,000 mile cross-country road trip. (This kind of thing never happens close to home, so always be prepared). After the clog was free I filled our trash can, about 7 gallons, and dumped it into the toilet to force flush out the debris. I did this 2 or 3 more times.
  • Add a holding tank treatment to the rv waste tank, fill it with water and let it sit for a few hours. This will help break down any solid waste that may be stuck to the sides of the tank.
  • After a few hours, flush the RV tank again with clean water to remove the cleaning solution.
  • If the tank is still dirty, you may need to repeat this process.

You might also want to invest in a tank rinser tool. These rinse sticks attack to your hose and create a pressure-packed stream of water that can help dislodge anything stuck to the sides of your tank.

Cleaners and Deodorizers for Black Water Tanks

The best way to keep your sewage tanks smelling great is to use RV friendly cleaners and deodorizers. As you may have gathered from above, your RV sewer system is much different than the plumbing in your house and requires additional care and precautions to keep it in top shape.

Always consult your owner’s manual or inquire with your dealer to confirm what you can and cannot use in your RV plumbing system. We prefer single use bottles of deodorizer and cleaner that we dump into the toilet, with a few gallons of water, after every dump. I’ll add one to the gray tank at the beginning of a long trip or if we get any smell coming from the sinks. Deodorizers are available in bulk bottles, individual use bottles, powders, powder pods and liquid pods.

Campa Chem RV Holding Tank Deodorant

There is one tip in particular we’ve come across while searching for a way to really clean our tank after the ill-fated non-RV toilet paper incident (can you tell yet that I was mildly scarred by that trip??) and that was the ice trick. You simply dump a bag of ice down the toilet bowl with a few gallons of water, before you begin to drive. As you drive, the ice sloshes around and supposedly beats (gently) the debris stuck to the tank walls and bottom. It melts and you dump it out as usual. We did notice our level gauge did not work for a little while after doing this, so we can’t say that it is a totally safe method, but it did seem to knock a bunch of the papier mâché mountains loose for us.

Some other tips we’ve come across:

Again, always consult with your manufacturer or dealer before trying any of these cleaning hacks. You want to be sure you don’t damage any equipment, gaskets or seals.

How to Keep Your Black Water Tank from Stinking

Easy… follow all the above steps. Dump regularly, keep it clean and use only RV friendly cleaners, deodorizers and toilet paper.

By following these simple tips, you can easily keep your RV’s black water tank clean and fresh with minimal effort. There’s no need to be worried about using the toilet while you’re out on the road!

Cleaning your black water tank is not a pleasant task, but it’s important to do it regularly to keep your RV in good working condition. Doing so will help you avoid problems down the road (or on the road) and enjoy your RVing trips to the fullest!


RV Black Water Tank PIN

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