How to Clean an RV Holding Tank: 7 Tested Methods that Actually Work!

On one of our first RV adventures, my son threw half a roll of toilet paper, tube and all, down our RV toilet. Luckily for me, it was wedged just shy of the abyss that is our RV black tank. I was able to reach down and save it from obscurity. I’ll never look at my hand the same way again.

As a full-timer with a family of 6, it got me wondering, “What else is down there? And how do you get it out?”

Cleaning your black water tank is a rite-of-passage for RV owners. Solutions include a black tank rinse every after flush, organic enzyme treatments, reverse flush pressure washing, and borax bath bombs!

Orange Sewer Tube Hook Up

Why Clean Your RV Holding Tanks?

When you clean your tanks, you also clean your RV sensors. Toilet paper, sludge, and wayward hygiene products can cover up sensors and give you false positive readings. If your sensors are off, you may be emptying too early, or waiting too long.

You want to dump your black tank when it is at least 2/3 full. Never leave your waste valve open when hooked up to a sewer site!

When it comes to the black tanks, water is your friend. A dehydrated black tank can allow sludge to pile up and solidify. Never poop in a dry black tank! Add a few gallons of water first.

It is a rewarding feeling to see when your control panel reads, “ALL TANKS EMPTY.” It’s a close second to the relief from setting up the last tiki torch at your campsite.

Lastly, consider Murphy’s Law. When do you think you will find out you have a plumbing issue? Either while you are preparing to depart for a vacation, or when you just pull into a campsite for the night. Come on! You earned this vacation; don’t ruin it with unattended plumbing issues.

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How Do You Clean Your RV Black Tank?

I always ask this question when I meet veteran full-timers. I love gaining knowledge and being reassured my efforts are enough. And every once in a while, I hear a method so crazy, it just might work!

Black Tank Water Fill Hose

My Preferred Method: a Black Tank Rinse

I’m a firm believer that an ounce of prevention is worth a pound of cure. The following method is my secret sauce, my go-to method for keeping my tanks clean and my sensors reading accurately.

It’s a black tank flush. It’s simple, but if you do it every time, you’ll avoid the need for more complicated solutions.

  1. Attach a dedicated garden hose to your black tank flush valve. Mark sure you mark this hose as for the black water tank use! Never use your drinking hose to perform a black tank flush.
  2. After emptying both your RV black tank and your RV gray tank, close the black and gray tank valves.
  3. Let the water run for 5-10 minutes and then open the black tank valve. Set a timer or have someone monitoring the toilet inside. Don’t let this overflow! Bad things will happen. Watch the water through a clear sewer elbow. It should come out clean and clear.

Psst … Not sure how to empty your tanks? Check out my other article on emptying my tanks, with pictures!

I repeat this process as needed based on the clarity of water flowing through the elbow and the readings on our control panel.

Now, what if you don’t have a black tank rinse? Or, ahem, you haven’t cleaned your tanks in a year or two? Check out some of these other solutions below, tried n’ tested by full-time RVers like me. Hint: Some work better than others.

7 Tested Methods for Cleaning an RV Black Tank

20-lb Bag of Ice

“Shaken not stirred?” This involves pouring 20 lbs of ice down your tank prior to departure. It’s easy to visualize why this would work. Ice, sloshing around, breaking apart any sediment on the walls. I only tried this method one time. It was quite cumbersome pouring 20 lbs of ice down an RV toilet. I’m also pretty sure it melted by the time we left.

RV Tank Wand

Toilet Tank Rotary Rinser Wand

Think of these as a water pick for your black tank. The wand is inserted into your RV toilet shooting high pressured streams of water throughout the black tank. It’s like a garden sprayer inside your tank, and very effective for getting rid of toilet paper clogs. Every RV dealership carries them, or buy one at Amazon.com. Here’s my recommendation.

Reverse Tank Flush

RV Toilet Treatment

This method forces water under pressure through the RV waste valve, drain pipe, and into the holding tanks. If you have mineral deposits, this might be your only option to get rid of them. You can either attempt it yourself with a plumber’s snake and water sprayer or hire a professional tank cleaning service.

Happy Campers

Happy Campers Tank Treatment

Happy Campers is one of many tank treatments on the market. These products claim to eliminate odors and break down waste. Happy Campers has a money-back guarantee that their product will do what it claims – AND it’s organic! I’m not sure how you go about proving it does or doesn’t. (I’m just going to take their word for it – 7,000 customers can’t be wrong!)

RV Tank Bombs

My inner child loves to see things blow up like mentos and soda. Unfortunately, the only excitement you get from using one of these is seeing a different color through your clear RV waste connector. RV tank bombs are drop-ins are cool brand names for concentrated treatment packs. Picture a bath bomb or a Tide Pod.

You drop these bombs down your toilet (hehe). Check out more info about RV toilets at my other article.

Most of these are some blend of detergents and acids to break down fatty and oily deposits. Some bath bombs and other treatments pack powerful natural enzymes designed to break down natural waste in short order.

Dawn Soap + Water + Drive

This is our modified version of the Geo Method that we use on both our black and gray tanks. Some versions of the GEO method call for harsher chemicals such as: chorine, bleach, Pine-sol, Borax, Calgon and even Vodka. I shy away from putting anything more than Dawn soap. I’m trying to prevent plumbing issues not cause them. This method can be used for both black and gray tanks.

We also prefer to use Dawn soap because it’s my wife’s name. “Kids, I’m flushing Mommy down the toilet again!”

Never gets old.

By the way, some DIY black tank cleaning solutions will recommend you use bleach, hydrochloric acid or some other caustic cleaner for your black tank. In general, bleach is a bad idea. You need to cultivate a biome of healthy bacteria in your tank so microbes break down the waste. Bleach and other caustic chemicals kill these microbes.

DIY Treatments

In my research, I found everything from do-it-yourself tank wands to I-saw-this-on-YouTube black tank bombs. I’m not comfortable going this route (I can picture my kids whacking each other with lightsaber-inspired DIY tank wand).

Here’s a popular recipe courtesy of Kleen Tank cleaning service:

  • 1/3 c Borax
  • 1/3 c Baking Soda
  • 1/3 c Citric Acid
  • 1 tsp. Water

Mix all ingredients in a Ziploc bag and add just a few drops of water to allow the ingredients to bind. Not too much water, or you’ll get a soup, not a bomb! Pack tightly in silicone molds or muffin tins, and let dry overnight. Store in an airtight container.

For lots more great RV tank cleaning information, check out Kleen Tank’s FAQ site here.

My kids would love making this, but I’m going to keep our chemistry experiments away from our black tank for now. Besides, I’d rather be fishing.

Psst . . . if you’re reading this content anywhere besides Ask The RV Engineer, it’s been illegally “scraped,” and you’re probably on a spam website. So please be careful! Don’t share any private information, and come back to us at www.askthervengineer.com!

RV Slicer Waste Valve
Poo Pourri Bottle

Quick Tips for the Dump Station

Be Courteous at the Dump Station

If I’m at a dump station and there are people behind me, I’ll normally skip the black tank flush. No one wants to spend their camping weekend waiting in line to dump poop.

Use the Correct Water Supply

Some dump stations have water to perform black tank flushes as well as water to fill your fresh water tank. Be careful not to confuse the two and pray that nobody before you confused them either.

Hydrate! Hydrate! Hydrate!

Your black tank is thirsty. You don’t want solids going into a dry tank. Putting a few gallons of water into the black tank is on our RV setup checklist, and it should be on yours as well.

Do You Need RV Toilet Paper?

Science tells us “No.” Wandering Weekends put several brands to the test (see video below). Great value septic safe was found to be the best RV toilet paper based on value, comfort, and being able to dissolve.

Never throw wipes down your RV toilet even if they say flushable. Just toss ‘em in their trash can.

Many RVers don’t flush their toilet paper. Instead, they place used toilet paper in your bathroom trash can. While kinda gross, it does make sense. I’m still not doing it. Everyone has their limits, alright?!

For Help, Ask a Professional

Everyone I’ve met on the road is happy to share their tips, take a look at your set up and show off their own. I try to take in all the knowledge I can, filter out the crazy and use what works.

The toilet paper incident has me watching the bathroom like a hawk. I can’t trust that my kids will keep foreign objects out of the black tank, but I have confidence in the methods we use to keep our tanks clean.

However, I’m getting worried. Apparently, my kids all are training to become professional eaters. Before long, I’ll be spending half my day waiting in line at the dump station.

Michael Huff: Full-time RVer, husband, father, son, brother, friend and dreamer. I am officially “living the dream:” traveling the country with my amazing wife, four awesome kids, and beloved boxer in our 150-sf RV. Each day we are learning, laughing, (maybe a little yelling) and finding the good in this world.