How To Clean Out An RV Black Water Tank (5 Simple Steps)

If you haven’t been thoroughly cleaning your RV’s black water tank, all the air fresheners in the world won’t hide the bad smell.

That’s because a black water tank is the equivalent of a home’s septic tank and a lack of cleaning it will lead to its content’s stink wafting back into your RV.

Even worse, a neglected tank can lead to plumbing issues and breed dangerous bacteria that could prove harmful to anyone using the RV.

Luckily, deep cleaning your black tank doesn’t have to be a tedious and messy job with our simple 5 step plan!

Let’s begin.

How To Clean An RV Black Tank

Step 1: Prepare for the Job

Your black tank’s contents are hazardous, so you should avoid inhaling any fumes or letting any of it get on you or your clothing.

Before starting with the cleaning process, protect yourself by wearing rubber gloves and protective glasses. Shoe covers and a face mask are optional, but recommended protective gear, as well.

Just in case, have soap and running water ready nearby for cleaning up after the job. Avoid bringing contaminants into your RV by cleaning up outside.

Step 2: Empty the Tanks

After wearing your protective gear, the first step in the cleaning process is emptying the RV tanks.

We recommend doing this before the tanks become too full, or else the excess content might damage the tank or plumbing and lead to your black tank leaking. If the tank is too full, you also can’t add water to liquefy solid waste and prevent clogs while draining.

On the flip side, make sure your tank is at least 2/3rds of the way full. Emptying your tank too often can leave solid waste behind. When it’s full, it’s easier for the solids to breakdown and empty out.

After adding water to your black tank, park your RV beside a sewer outlet, which you’ll find at a campsite or dumping station. If you are emptying the tank at your house, check out our guide on how to dump an RV black tank at home.

Hook your sewer hose up to your RV and then to the dump station inlet. The bayonet-style end goes in your RV while the “L” shaped elbow end will go in the dump station inlet. Check out our guide on how to properly hook up a sewer hose for more information.

Tip: Use an RV sewer hose support system to create a downhill effect for your hose. This will help for sites where the ground slopes uphill to the dumping sewer inlet.

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After setting up the sewer line, follow these steps:

  • Close the black water tank and gray water tank valve, then fill the gray tank with water.
  • Open the black tank valve to empty it.
  • Once it’s empty, open the gray tank valve and let its water flush the sewer hose clean.

To avoid running into trouble with other campers while draining your black tank, stick with these tips:

  • Be polite to others at the dump station. Unruly behavior has led to the closure of dump stations across the country.
  • Don’t use harmful chemicals, such as formaldehyde, to flush your waste tanks. It damages your tank and equipment at the dump station.
  • Close the black valve until you are ready to dump and again immediately after dumping is complete.
  • Don’t use the RV’s drinking water hose to flush the black water tank or sewer hose. Using it for such purposes can contaminate your fresh water source.

Step 3: Soften and Remove Waste Tank Buildup

Removing waste tank buildup is something you should do at least once a week. If not, the waste can cake to the side of the tank, causing blockages, odors, and other problems.

After emptying the waste tank, lock the drain outlet and begin the buildup removal process by flushing the toilet until 3/4 of the black tank is full.

Next, we simply need to use your black tank treatment of choice, whether that be a liquid enzyme cleaner, your own homemade holding tank treatment, or two cups of liquid bleach into the tank via the toilet.

Note: Contrary to popular opinion, bleach, when used correctly will not hurt your tank or plumbing when diluted and used correctly. Be sure to not let the water/bleach mixture sit for more than 10 minutes and completely rinse out the bleach.

Give the mixture 10 minutes (no longer) to soften the caked waste within your tank and sterilize it. After 10 minutes, drain the tank’s contents and immediately fill it with water before emptying it again.

If using bleach, keep doing this until the bleach smell completely disappears, and you can’t see debris passing through the clear hose adapter. Making sure the bleach smell is gone ensures no bleach residue damages your plumbing or tank.

If you regularly perform this step (weekly) then more often than not your tank will be thoroughly cleaned out and you can skip ahead to step 5. However, if you still have build-up in your black tank we will need to backwash it, as described in step 4.

Step 4: Backwash the Black Tank

Backwashing is a thorough cleaning process that eliminates all waste from the black tank’s walls and floor with pressurized water. Even hardened caked waste can’t withstand this cleaning, especially after the earlier bleach cleaning.

Depending on your RV’s design, you can backwash the tank with the built-in rinser system or buy a handheld backwasher that attaches to a water hose.

Using the Built-In Rinser

If your RV comes with a built-in cleaner, plug it to a water hose and open the coach’s pressure washing valve. Let the system keep running until you see clear water running through the clear hose adapter. But note that this is just a general guide as built-in rinsers vary between RVs. You can consult your RV’s rinser manual for more detailed information on this stage of how to clean out your RV black water tank.

Using a Handheld Backwasher

Most handheld systems come in the form of a wand that you can stick down the toilet to pressure wash the tank. To use the wand:

  • Attach it to a water hose that’s plugged to a tap
  • Close the tap until the wand is down the toilet
  • Once the wand is in the tank, open the tap
  • Move the wand around the tank to pressure wash every possible corner
  • Keep going until the waste passing through the clear hose adapter is debris-free

How quickly and effectively you can do the job with a handheld backwasher will depend on the product’s quality. We recommend the Camco Flexible Swivel Stik.

Camco RV Flexible Swivel Stik with Shutoff Valve

Camco RV Flexible Swivel Stik with Shutoff Valve

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Macerator System

A macerator system connects directly to your TV waste outlet and not only allows you to drain your tank for longer distances, but it can also flush your tanks out.

The system sprays high-velocity water to peel off the accumulated waste and flush the black water tank. You can also use it to clean the sewer hose.

Flojet Portable RV Waste Pump

Flojet Portable RV Waste Pump

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Flush Valve

It does the same job as a macerator system and also comes with a built-in backflow preventer. It’s so effective it can break and clean clogs, as well as clean your tank sensors.

You can get a flush valve that you can install or uninstall without tools for each use. Alternatively, you could go for the option you can permanently install on your RV and connect to the tank.

Camco Rhino Blaster Sewer Tank Rinser with Gate Valve

Camco Rhino Blaster Sewer Tank Rinser with Gate Valve

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Step 5: Prepare The Tank & Toilet

The last step in our How to Clean Out an RV Black Water Tank guide is preparing the toilet and tank for use until the next clean.

Firstly, shut all the drain pipes to avoid leaking waste everywhere you take your RV. After that, fill and flush the toilet four to five times to fill the black tank’s bottom. If you don’t do this, the first waste that goes in will solidify and stick to the bottom, which will cause clogging issues later on.

When there’s enough water, add an eco-friendly enzyme cleaner.

Bio-Pak Natural Holding Tank Deodorizer and Waste Digester Drop-Ins

Bio-Pak Natural Holding Tank Deodorizer and Waste Digester Drop-Ins

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Enzyme cleaners use macromolecular biological catalysts (enzymes) to accelerate the breakdown of waste. Aside from liquefying waste to prevent clogs, enzyme cleaners also prevent odors. These benefits will work together to make your next black water tank cleaning far easier.

Also, unlike products that contain formaldehyde or other harsh chemicals, enzyme cleaners don’t damage water tanks or other aspects of your plumbing. You can get it as a liquid, tablet, pouch, or powder to suit your preference.

Bio-Pak Natural Holding Tank Deodorizer and Waste Digester Drop-Ins

Bio-Pak Natural Holding Tank Deodorizer and Waste Digester Drop-Ins

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Final Tips on How To Clean Out an RV Black Water Tank

That’s everything you need to know about how to clean out an RV black water tank. But don’t forget, during steps 2, 3, and 4, your black tank drain must remain connected to the sewer drain. If not, you could end up with a nasty mess on the ground (or worse, on you)!

Camco RV Flexible Swivel Stik with Shutoff Valve

Camco RV Flexible Swivel Stik with Shutoff Valve

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You also need a clear sewer hose adapter. Without one, the only way to see how clean the tank is during each flush is by opening the drain line while waste flows out of it. You don’t want that.

Also, when picking a handheld backwasher, take into consideration your toilet’s design. Straight tank rinsers are suitable for toilets with black tanks directly beneath them. If the tank isn’t directly under the toilet, go for a flexible tank rinser that can bend to enter the tank at an angle.

Camco 90 Degree Sewer Hose Adapter For Portable RV Waste Tanks

Camco 90 Degree Sewer Hose Adapter For Portable RV Waste Tanks

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