RV Black Tank Cleaning and Maintenance Tips

Can you guess what is the most hated RV maintenance chore is? If you’ve answered cleaning the RV black tank, you’ve guessed right! It’s a nasty job but someone’s got to do it. Is it going to be you? But what if you don’t even know how to empty, flush or clean your holding tanks?

Properly caring for your RV black tank will mitigate costly repairs and headaches down the road. So, let’s roll up those sleeves, put on your doctor gloves and let’s get to this crappy chore!

RV Black Tank Cleaning and Maintenance Tips

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First, let’s learn about your RV sewer system. And, after we’re finished, we’ll throw in a few great black tank maintenance tips to keep it smelling fresh and clean.

About your RV Holding Tanks

Recreational Vehicles have three different tanks. Your RV water tank obviously holds your motorhome’s or camper’s fresh potable water.

The gray tank collects the dirty gray water from showers, washing hands, and dishwashing.

Your RV black tank holds whatever goes down the toilet. That said, some smaller RV’s bathroom sinks may empty into your RV black tank.

Each tank has an electronic sensor that is supposed to indicate available capacity on your sensor control panel inside your RV. However, more often than not, debris from waste collects on those sensors; giving false indications on your gray and black tank readings.

Always On Liberty - RV Holding Tank Level Indicators

To help alleviate that issue, you need to clean your tanks frequently to get rid of debris (sludge, paper, calcium, etc.) so your readings will be accurate. 

It’s extremely important to keep all of your RV tanks clean and properly maintained or you’ll suffer nasty consequences caused by piling (piled up crap and toilet paper) and clogs caused by piling.

There’s controversy of whether to keep your RV’s gray tank open vs. closed. We keep ours closed per professional advice from our friend, Jim, owner of Kleen Tank RV Tank Cleaning Service.

He also recommends to wait until your black tank is at least two-thirds full before dumping.

When hooked up to sewer, it’s important to keep both gray and black tank valves closed until dump time as to not allow any waste to solidify or dry out in your RV’s sewer hose and connections.

How to Empty and Flush your Gray Tank and RV Black Tank

Always On Liberty - Dan with Rubber Gloves

1. Put on your big kid gloves

On RV black tank maintenance and dump days, put on your disposable gloves before getting started because face it, this job is nasty! 

2. Get out all your RV sewer accessories

After putting on your gloves. You’ll need to get out your RV sewer hose and accessories:

DO NOT use your blue or white drinking-water hose for flushing your tanks! 

Let all occupants know not to use the bathroom during this process.

3. Tank Valves

Like we mentioned earlier, it’s recommended that you keep your tank valves closed. If you don’t, then close both, the black tank and the gray tank valves the right before cleaning. 

4. Install Sewer Hose and Attachments

Remove sewer pipe cap on RV sewer discharge port. Attach your clear sewer hose adapter to one end of the sewer hose. Then attach that to the RV sewer discharge port.

5. Connect your hose

Attach RV bayonet elbow fitting to the other end of sewer hose and insert end into the sewer hole in ground. Make certain it’s secure. If it isn’t stable, place a heavy object on top to hold it into the hole.

6. Open black tank valve and let ‘er rip!

Open black tank valve first to discharge contents completely. 

7. Open gray tank valve to flush

Open gray tank valve to discharge gray tank contents. This will also flush out existing black tank residuals from sewer hose.

8. Hook up water

Hook up all-purpose water hose to water spigot and black tank flush port. Turn on water at spigot to flush black tank until water runs clear through clear sewer hose adapter.

9. Secure water

Shut water off at spigot. Close black tank valve.

10. Disconnect hoses and attachments

Wait until water is completely flushed and sewer hose is empty before disconnecting clear sewer hose adapter and bayonet attachments. Stow sewer hose and attachments. Re-attach cap on RV sewer outlet port.

11. Clean toilet and add chemicals

Go inside and add one gallon of clean water into toilet bowl. Flush into black tank. Add second gallon of water to toilet bowl with toilet cleaning solution and clean with toilet brush. Add in rv holding tank treatment and flush into black tank to prevent piling.

Always On Liberty - Black Tank Empty and  Flush Procedure

Back Flush Method

The back flush method should be done at least once a month if you’re full-time RVing.  And if you’re part-time or weekend camping, you should back flush at least quarterly to semi-annually.

After your initial dump and rinse, you’re going to close all valves and fill your black tank with water. Then you’re going to repeat steps 6-8 above.

The idea is to use as much water as possible to clean your RV black tank. The end result should be the water that flushes from your tanks to be clear

Some RV’s have a factory installed back-flush system. If you don’t have a factory installed back-flush system, you can easily install aftermarket systems.

Black Tank Treatment

As we’ve mentioned earlier, after you’re finished flushing your RV sewer system, then it’s time to add in the black tank treatment.

There’s three different black tank treatments you can use; the Geo Method, the Dawn Method or just us a commercial product.

The RV Black Tank Geo Method:

The GEO Method also breaks down water surface tension. We just flush it down your toilet. This ensures we won’t create the infamous poop pyramid in the bottom of the tank.

The environmentally safe GEO Method also cleans scum and prevents hard water deposits on the sensors.

You’ll need an empty five gallon bucket, 1 cup Calgon water softener, 1 cup Borax powder and 4 gallons of hot water. Then, mix Calgon, Borax and hot water in bucket thoroughly. Dump entire bucket of mixture into the toilet and flush.

The RV Black Tank Dawn Method:

Another is the Dawn method which is just as simple and supposedly performs similar to the above Geo Method.

In your toilet, just add two capfuls of Calgon water softener and about 1/2 to 1 cup of liquid blue Dawn dish detergent. Flush well.

RV Black Tank Commercial Product Method

If you prefer to use a easy drop-in black tank treatment, we recommend Happy Camper.


Which toilet paper should you use?

Toilet Paper

It’s extremely important to use only septic-safe dissolvable toilet paper. Now, I’ll say this here. You don’t need to buy expensive RV toilet paper you see at the camping stores or RV section in big box stores. Just remember, when using your RV black tank, “AFTER YOU GO, ADD LOT’S OF H2O!!”

Tank Maintenance Tips from the Pro


Here’s what Kleen Tank recommends for tank maintenance:

Before leaving for your RV trip:

Fill gray and black water holding tanks about 1/3 full of fresh water. The sloshing motion of your moving RV combined with the water in the tanks will help break down solids, gently clean the tanks and help with the overall health and maintenance of your RV’s waste holding tanks

During your trip or while using your RV

Always keep both tanks closed (as we also mentioned above). Also, your tanks’ sensor panel should read 2/3’s to full before dumping.

If they don’t but you still need to dump because you are headed out to camp off the grid or boondock, you’ll want to top off both tanks with fresh water for an accelerated exit flow.

Also, anytime you leave the campground, dump the gray and black tanks and again. Fill each 1/3 full of fresh water for your trip home or next destination.  This will help keep your tanks lubricated and the sloshing will minimize damage and repairs.

After your RV trip:

Top off both tanks with fresh water and dump before storing. Be sure to winterize your water system (if applicable) and add a lubricating antifreeze to tanks before storing long-term. This is a critical maintenance necessity.

Always On Liberty - RV Tank Management - Trip Planning

Final thoughts on cleaning and maintaining your RV Black Tank

Lastly, before signing off from reading how to clean and maintain your RV black tank, take a moment to watch our video interview with a RV tank specialist on how to take care of our RV holding tanks. Trust me, you need to watch this!

Always On Liberty - Black Tank Maintenance Tips

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2 Replies to “RV Black Tank Cleaning and Maintenance Tips”

  1. Hi Guys. Thanks for the informative post. One question, you mention your method for cleaning out your BW tank (1 Cup Calgon Water Softener and 1 Cup Borax Powder) and Kleen Tank's GEO method (Pine-Sol with a half cup of Calgon Bath). Do both recipes accomplish the same thing? Also, you don't mention when you add the Kleen Tank slush to your system. Is this added just before leaving camp? Thanks!

    1. Jonah, thank for reading and paying attention to that. You can use one of the other. We use ours after we empty our tanks and flush really well.

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