How To Use an RV Black Tank Flush

Most modern motorhomes come with an RV black tank flush. This feature helps clean your RV’s black water tank after emptying its contents. If this feature is new to you, let’s talk about how to use an RV black tank flush. 

Why Use an RV Black Tank Flush?

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Most RV old-timers probably remember the days before this feature was commonplace. Without it, the best way to flush your black tank is to go inside and flush the toilet a bunch of times—filling your tank with several gallons of water—before emptying it a second time. 

Or, you open your bathroom window, run a hose inside, stick it down the toilet, and try to flush your tank out that way. DON’T TRY THAT! I’ve been there and done that—unsuccessfully.  As a result, I think I’m blacklisted from a certain Southern California RV park. But that’s a story for another time. 

Here are the benefits of an RV black tank flush: 

Eliminates the need to go inside to flush water down your toilet. Dislodges stuck toilet paper and solid waste. Clears holding tank sensors to provide more accurate level readings. Removes “leftovers” that can cause irritating odors. As a side benefit, it cleans out your sewer hose.

Where Can You Use an RV Black Tank Flush?

Photo by Benjamin Clapp via Shutterstock

Campgrounds with full hookups and RV dump stations are the best places to utilize your black tank flush. They offer the two main things you need to get your black water tank clean: a place to dispose of your waste and a source of clean water to clean out your tank. 

If you happen to have a sewer clean-out on your property that’s accessible with your RV sewer hose, you might be able to do this at home. But doing it at a dedicated facility makes it much easier and eliminates the potential for making a mess in your backyard. 

How Often Should You Use an RV Black Tank Flush?

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You can use your RV black tank flush every time you empty your RV holding tanks. But using it that frequently isn’t required. If you’re looking to save a little time, make it an RV maintenance task you do at the conclusion of each camping trip. 

When you know it’s the last time you’ll be emptying your holding tanks before heading home and unloading, take the extra time to deep clean your tank with a full flush.  That way, you won’t leave waste residue in the tank while your RV is sitting idle between trips. 

How To Use RV Black Tank Flush

Although you’ve already emptied your holding tanks, it’s a good idea to keep wearing disposable or reusable rubber gloves for this procedure.

Step 1: Empty Your Holding Tanks

It’s important that you dump your black tank before utilizing this flush mechanism. So you’ll want to connect your sewer hose and empty wastewater completely before you go any further. 

Here’s a quick overview of the process for emptying your tanks: 

If you prefer written instructions, check out our step-by-step guide to emptying RV holding tanks.

Step 2: Locate The Inlet

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Once you empty your holding tanks, leave your sewer connection attached and move on to operating your black tank flush valve. 

The inlet for your RV’s black tank flush is located on your RV’s exterior wall. Typically, it’ll be next to your city water and cable connections. If you’re having trouble finding it, consult your owner’s manual. 

Step 3: Connect a Water Hose

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You can use a standard garden hose, but make sure it’s a different hose than the one you utilize for connecting to city water or adding water to your RV’s freshwater holding tank. 

Connect one end of the hose to the black tank flush inlet and the other end to a nearby water source. 

Step 4: Open Your Black Tank Handle

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This handle should already be open if you just finished emptying your holding tanks, but if you’re running a black tank flush on a tank that’s been sitting empty for a while, be sure to open the handle completely. 

If it isn’t, water will fill your black tank quickly and could overflow into the RV or cause other issues with the tank itself. Leave the handle for your gray water tank closed during this flush process. 

Step 5: Run Water Through The Tank

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Open the handle on the spigot for your clean water source. Water will run into the flush mechanism, through the black water tank, and out your sewer hose. Open the spigot partially at first to check that everything is working as expected before opening it completely. 

Flush your tank with water for 2-3 minutes, or until the water running through the sewer hose is clear. Having a clear 90-degree connector at the end of your hose is handy for visually checking when the water is running clear. 

Step 6: Turn Off Water and Disconnect the Water Hose

After flushing, turn off the water at the spigot and disconnect the hose from your flush inlet. Water will continue to drain out of your sewer hose for a short period after you’ve disconnected. When you no longer hear anything running through your sewer hose, close the handle for your black water tank.

Step 7: Empty the Sewer Hose

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Leave your sewer hose connected for this step. Starting at the end closest to your RV, lift the sewer line to empty any remaining contents towards the sewer hookup. Work your way towards the outlet, using gravity to your advantage. You should hear any water remaining in the line emptying out. 

Be gentle to avoid damaging the sewer hose, which would require a replacement. But you may need to do this two or three times, depending on the slope and how much water is left in the hose. The line should be light when it’s empty and you shouldn’t hear any water jostling around when you shake prior to disconnecting. 

Step 8: Disconnect Your Sewer Hose

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Now you’re safe to disconnect your sewer connection and replace the cap on your holding tank outlet. Remove the end closest to your RV first and keep it high to avoid spills and drain any remaining water or waste. 

Follow these tips for caring for your sewer hose when cleaning and storing your hose after dumping. 

That’s all there is to it! Using your RV black tank flush regularly will help you avoid clogs and other not-so-rosy plumbing issues. It’s a super easy procedure that keeps RV toilets and septic systems flowing smoothly. 

Do you have any questions or ideas to share about using an RV black tank flush? Let us know in the comments below! 

If you’re still learning the ins and outs of RV maintenance, check out our downloadable RV ownership and maintenance booklet!