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How To Flush And Clean RV Black Tanks


Learning how to flush and clean RV black tanks is a topic that’s on every RVer’s mind. But waste water disposal is something few want to think about. However, if we want to keep the RV black tank odor-free and working properly, let’s get down to the basic steps.

The basic steps to flush and clean RV black tanks

Don’t let all the knobs and connectors scare you. It’s easy to flush waste water from your RV black tank.

Drain the black tank first. Always.

Once drained, close the black tank valve. Then open the gray water valve to empty it. The reason for this is to clean the hose attached from your wastewater tanks. Residue will go into the septic system at the campground. When finished, close both black and gray waste tank valves.

Go inside your camper and partially fill the tanks for a second rinse.

Run water into the toilet and the sinks. Then open the valves once again in the same order. This is to completely clean tanks and the hose.

  • If you do not have full hook-ups. Simply fill a couple gallon water jugs. Then pour water down your toilet and sink as a second rinse.

This is only the beginning to clean and flush RV black tanks. Keep reading to find out how keep the monitor system reading accurate. You always want to know exactly how much waste water is in the tank.

RV Waste Tank Dumping Tips

  • Use disposable plastic gloves to wear when performing the deed.  You’ll eliminate any chance of spreading bacteria if you toss the gloves before going into your RV.
  • Educate children, grandchildren and visitors on the importance of responsibly using an RV toilet. Nothing should go near or inside the toilet except a person’s butt, human waste and septic-safe toilet paper. 
  • Use septic-safe toilet paper. You can buy special RV toilet paper made specifically for marine grade and RV toilets. Or, choose Scott’s single-ply TP, which is septic-safe and can be used in RVs.
  • Pick an RV waste water tank cleaning treatment that you feel works best for you. Use it each time after you dump your black tank.
  • Clean your toilet and sinks only with earth-safe DIY cleaning products. When you clean your RV with vinegar, baking soda, and hydrogen peroxide you are being kind to the planet and septic systems.

Who knew, but there seems to be a hundred opinions of tried and true methods for keeping an RV black tank clean.  Maybe you’ve given a few of these a try or perhaps one or two will pique your interest.

The basic treatments to keep RV black tanks clean

Tools for how to flush and clean RV blank tanks
Try these methods to keep your RV black tanks clean

Ice Cubes and Detergent

The ice cube theory is one that’s been sloshing around for many years. Some folks simply add 2 to 3 bags of ice cubes into their RV tank and go for a drive. The theory has been expanded to include adding a quarter cup of dishwashing detergent (NON-antibacterial version) plus 2 gallons of water to the tank along with the ice cubes.

Dawn or Joy brand detergents seem to get the highest hits for the type of liquid soap to use. RVers then simply take a drive for 2 to 4 hours, then dump and flush at a full-hookup campsite. 

  • Do not overdo it with detergent. Or your RV toilet and sink might start foaming.

Baker’s Yeast and Peroxide

To get rid of solids and odor in the black tank, try baker’s yeast and peroxide. Add 1 gallon of water to an empty black tank, 4 oz. of yeast and 10 oz. of peroxide.

Take a drive, perhaps to your next camping location, while the water/yeast/peroxide splashes throughout your black tank. Empty the tank and refill with some water. Then add your normal black tank treatment additive.

  • This method has been reported to eliminate solids and odor, but not paper.

The GEO Method

Try is adding a water softener to the ice cubes and detergent treatment listed above. Calgon is a common brand people use. This is known as the GEO method. Many RVers use this method with much success.

Once your tank is empty and valve is closed, mix 2 cups water softener with 1 to 2 gallons of hot water for each tank.  Pour into your sink or shower for the gray tank and into your toilet for the black tank.

The water softener keeps gunk from sticking to the insides of your tank and to the sensors. This should keep them squeaky clean and giving accurate monitor readings.

You can also add 1 cup of the original “blue” Dawn dishwashing detergent. Or, add 1 cup of eco-friendly laundry detergent to the black tank when you add the water softener. This helps to further clean and deodorize the tank. 

  • Many RVers also include ¼ cup Borax to the black tank along with the detergent. Borax serves as an excellent cleaning agent.

Simply use your tanks as you normally do and empty when the tanks are 2/3 to full. All these products are safe and eco-friendly. The GEO method can be used on an “as needed” basis or each time you dump the black water tank.

Best RV Waste Water Tank Cleaning Tools of the Trade

Perhaps you like using one of the many RV black tank treatments that are on the market. But if you still see irregularities in the tank’s reading levels, these nifty tools can successfully flush and clean RV black tanks.

Built-in Waste Tank Rinse System

Many RVs have their own built-in rinsing system called a black tank flush. If yours has this option, it is performed by hooking a separate hose to the black tank flush inlet water valve. Leave the black tank valve open while performing the flush. This prevents water overflows into your RV sinks and toilets.

This system is comparable to power washing your black tank to thoroughly clean it  Refer to your owner’s manual for your RV for instructions.

RV Hydroflush

The next best thing to a built-in rinsing system appears to be the RV Hydroflush. Depending on your tanks’ location, there is a 45-degree version and a new 90-degree to fit the particular type tank connection.

The Hydroflush is a clear hard plastic piece which that attaches to your tank valve. This allows you to see through it as your tanks are flushing. Once clear water is continually running out, you’ll know that part of the job is done.

The Hydroflush has a fitting protruding from the bottom portion of it where your garden hose will connect to actually perform the flush. Once the RV tanks are empty, attach the Hydroflush directly to the tank valve. Then attach the drainage hose to the bottom fitting on the Hydroflush. Connect the garden hose to the Hydroflush and start blasting. Keep your black tank valve in the open position.

With the Hydroflush, it is suggested you flush the black tank first. But it can also be used on the gray tank once the black tank valve is closed and the gray tank valve has been opened. 

  • The Hydroflush comes with a pre-installed back flow preventer and separate anti-siphon valve. It protects the freshwater supply from any contamination.

Tornado Rotary Tank Rinser

This product truthfully has pros and cons. The results are similar to any built-in rinse system, but the downside is a rather technical installation process. You’ll have to drill a hole in your black tank to install it.

Reviews range from, best thing yet, to suggestions on making pieces out of brass as opposed to plastic which potentially can break, to it partially cleaned the sensors. Considering the installation involves drilling a hole in your black tank, properly placing sealant around that hole and then hoping for the best outcome, it seems to me there are better things on the market to try first.

Tank Wands

Tank wands make life pretty simple. You can clean and flush RV black water tanks by connecting the tank wand to an outside water hose. Run the hose inside your RV through an open window. Open the toilet bowl flush valve, stick the wand inside and down, to power rinse the inside of the tank. A valve on the handle controls water flow. Wipe the wand when rinsing is complete. 

Flexible wands maximize the effectiveness in power cleaning the tank, however, some tanks are located such that they require a straight wand.  Check the location of your black tank prior to making a purchase.  There’s even DIY tank wands to be found online.  Google for whatever best fits your needs if going the wand route.

  • There are several brands on the market, such as the Camco RV Flexible or Straight Swivel Stik or the Valterra Master Blaster, ranging from 23” to 42” long. Consider purchasing a tank wand with brass parts to avoid corrosion.

Quick Tips to Flush and Clean RV Black Tanks

  • Remember to also clean the “O” ring seals of your gray and black sewer caps.  You can then put a thin coat of grease on the seals to avoid any black or gray water dribbles.
  • After emptying the black tank, always add a bit of water to it. This keeps the tank and any residue from drying and hardening on the bottom of the tank.
  • Flushing and power washing the black tank is not necessary each and every time. You’ll find the right schedule essential for your RV.
  • Keep valves closed until you are ready to dump the tanks. This keeps any solids from drying out inside your tank. It also prevents odor leakage.
  • Do not dump your tanks until they are at least ½ full. Keeping enough water in the tanks enables solids to drain out.  You may need to add water to the tanks if you are departing a site and need to empty them, but they are not at least ½ full.
  • Never use your fresh water hose for dumping your tanks – EVER!
  • Purchase a clear RV dump elbow to attach to the tank valve. This helps you see when waste water looks clear.  Continue running water through the toilet until waste water is cleared.
  • Have a clogged black tank? Well, we wrote an article all about how to clean a clogged tank, which includes a step by step guide. Find the article here.

Conclusion

There are many methods and tools to flush and clean RV black tanks, and keep them working like they should. Find the one that works for you to keep odors away, waste water sensors working, and waste water vales flowing.

Author Nancy Ferri Avatar

Nancy Ferri

Nancy Ferri is recently retired. She and her husband are avid campers who plan to hit the road next year to enjoy some longer adventures throughout the U.S. They also enjoy kayaking, hiking and bicycling in the great outdoors.

10 thoughts on “How To Flush And Clean RV Black Tanks

  1. Excellent advice. I’m in the market for an RV and need to learn before I buy. And this information was fantastic. Thank you!

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  6. We were told to use Borax, along with Calgon and Dawn. I noticed that the borax doesn’t break up very well…and wondered if you have ever heard of it clogging the holding tanks by solidifying? Should we just stick to powdered Calgon and Dawn?

    1. Dissolve the Borax in a gallon of hot water in a bucket or big pot, then pour it in the toilet with Calgon and Dawn.

    2. We have been using borax and dawn dish soap. We put the dawn and borax in a gallon of water, mix well. Then let sit overnight and shake again. It all seems to dissolve after sitting in the water overnight.

  7. Hello, I was wondering if you had any tips or tricks for cleaning the neck area of the toilet itself. We recently became full time rv-ers and I’m noticing a build up in the toilet neck, going down the shoot.

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