How to Unclog a Compacted RV Black Tank

Dealing with a clogged black water tank, also commonly known as a compacted tank, might be one of the scenarios you fear most as an RVer.

Whether you’ve just heard about them, or you’re currently dealing with one, you may already know how frustrating these clogs can be — nothing will drain out of the tank, waste can back up through the RV toilet, and suddenly, your RV bathroom becomes unusable.

However, unclogging a compacted black water tank isn’t as bad as it may sound, and only requires following a set of easy-to-follow instructions.

In this guide, we’re going to explain what a compacted black tank is, how to fix clogged RV black tanks, and how to prevent black tank clogs in the future. Let’s get started.

Key Points About Unclogging RV Black Water Tanks:

• Diagnose Your Clog:Make sure that you actually have a compacted black water tank before you start the process of clearing it – other black tank clogs require different methods to fix.
• Misreading Sensors:Sometimes, holding tank sensor probes can falsely indicate that you have a clog, when you actually don’t.
• How to Fix Compacted Black Tanks:Unclogging a black water holding tank is as simple as letting a full tank of water and a high-quality, bio-enzymatic treatment, like Unique Clear-It, work on breaking down the clog for several days until you’re able to dump the tank.
• Stubborn Clogs:If the clog is really severe, you may have to repeat the treatment process a few times before the RV black tank clog is fully cleared.

What is a Compacted RV Black Water Tank?

Compacted RV black water holding tanks typically occur when waste, toilet paper, and debris accumulate, and harden, at the bottom of the black water tank. When this happens, solid waste blocks the exit and nothing can flush out of the tank when the black tank valve is opened.

Compacted tanks often occur when an RV is stored with full black tanks. Over time, the liquid waste evaporates (or leaks out of faulty valves) and the solid waste is left behind and hardens into a solid brick of poop and paper.

If you aren’t sure what is causing your black tank to be stopped up, please review our guide: What Kind of RV Toilet Clog Do I Have?

How to Determine What’s Causing Your Clogged Black Tank

Before trying to diagnose what’s causing your RV black tank to be clogged, we highly recommend being in a location with access to a sewer port, such as a full-hookup campground or dump station. This will give you the opportunity to do a more thorough diagnosis.

Now let’s dive in and figure out what type of RV toilet clog you have:

1. Use your senses to check your RV.

If your RV has been parked for an extended period of time and you are greeted with an overwhelming odor, it’s possible that the black tank was not dumped before being put in storage.

If the odor gets stronger as you approach the camper bathroom, it may indicate that you have a compacted tank.

2. Turn off all water sources to the RV.

3. Look down the toilet with a flashlight to check for buildup.

When looking down your RV toilet, check for the following:

• Do you get a puff of odor when you open the toilet ball valve?
  • If the answer is yes, you likely have a pyramid plug.
• Do you see that the pipe is completely blocked off with paper debris?
  • If the answer is yes, you probably have a blocked toilet line.
• Do you see waste and toilet paper build up below the pipe but not touching it?
  • If the answer is yes, you probably have a compacted tank.
• Do you see the floor of the tank?
  • If the answer is yes, this may mean that you have misreading sensors.
• If you have plumbing fittings between your toilet and black tank, you may not be able to see into the black tank.

4. Move to a location where you can safely drain the holding tank.

A full-hookup campsite is recommended, because there may be a line behind you at the dump station which can interrupt the rest of the process.

5. Connect the sewer hose to the discharge port of your RV.

We recommend having a clear elbow, or sight glass fitting, so you can easily see what is coming out of the black tank.

Unfortunately, not all sewer hoses come with these, and it’s important to be able to see what is exiting the tank.

6. Open your black tank valve.

If water flows out of the tank when you open your black water tank valve, then you may simply have misreading sensors.

If nothing flows out of the tank when you open the black water tank valve, you may have a compacted tank.

7. Add water to your black tank through your RV toilet bowl.

• Does the water collect in the toilet bowl when you push down the flush pedal?
  • If the answer is yes, you may have a pyramid plug or blocked toilet line.
  • If you’ve left your black tank valve open for any period of time, you may have a pyramid plug.
  • If you never leave your black tank valve open, you may have a blocked toilet line.

• Does the water easily flow into the black water tank? If the answer is yes, you may have a compacted tank or misreading sensors.

8. Turn the water sources to the RV back on.

Once you’ve determined that you’re dealing with a compacted black tank, now we can help you resolve the problem.

Misreading Sensors or Clogged RV Black Tank?

Black water holding tank sensors that become coated with waste, toilet paper, and debris can sometimes misread and falsely indicate that you have a clog.

For example, misreading sensors may tell you that the black water tank is full, but then nothing comes out when you open the black water tank valve. This could signal that you have a compacted black water tank, but it could also mean that you simply have an empty tank with sensors falsely reading that the tank is full.

If you haven’t confirmed the type of RV clog you have, we recommend following our helpful diagnostic guide: What Kind of RV Toilet Clog Do I Have?

In some situations, it is even possible that you’re dealing with a clog and misreading sensors at the same time.

Fortunately, resolving these issues is relatively easy. For help with misreading sensors, reference our guide: How to Clean and Restore RV Holding Tank Sensors

How to Clear a Compacted RV Black Water Tank

Initially, compacted RV tanks may be a little easier to start fixing because the toilet line isn’t blocked, allowing you to add plenty of water and treatment to your black water tank.

However, if the waste and toilet paper has been allowed to sit for extended periods of time (if the RV has been in storage for example), they can become extremely hard and solid, increasing the time and effort it will take to remove the clog from the bottom of the tank.

Step-by-Step Instructions for Uncloggling a Compacted RV Black Water Tank

Now that you’ve identified that you have a compacted black water tank, it’s time to clear it with these easy-to-follow instructions.

Step 1: Close your black water tank valve.

You should always keep your RV’s black tank valve closed unless you’re actively dumping.

Learn Why:Why It’s Crucial to Keep Your RV Black Water Tank Valve Closed.

Step 2: Fill your black water tank with as much water as possible.

Water is the best thing you can add to your black tank. Using plenty of water helps prevent clogs, block odors, and keep your sensors functioning properly.

Additionally, the waste-digesting, aerobic bacteria in high-quality black tank uncloggers, like Unique Clear-It, need water to survive, and use the water to reach the waste they are intended to break down.

Note:Depending on how compacted the holding tank is, it may take several attempts to get enough water in the tank to allow treatments to work. You may need to add water and tank treatments several times to clear the clog.

Learn More:Why Using Lots of Water in your RV Toilet and Black Tank is Crucial

Step 3: Pour one entire bottle of Unique Clear-It down the toilet and into the black water tank.

Clear-It is the strongest, most effective RV black tank unclogger on the market — it really is!

The proven formula is powered by a boosted blend of fast-acting enzymes and extra-strength bacteria that work quickly to break through and digest the solid waste that is causing your RV’s black tank to back up.

While other uncloggers make promises, Unique Clear-It even works on old, compacted tank clogs from years of neglect, and breaks through them with ease.

Step 4: Let the full tank of water and Clear-It sit for at least 72 hours, or longer.

We always recommend letting Clear-It work for at least 72 hours, but for more severe clogs, you may need to let the treatment sit for much longer.

Stubborn clogs may need Clear-It to work for several days beyond the initial 72 hours to fully break down the clog. There is no amount of time that is too long to let the treatment sit as it will not damage tank components in any way, in fact, the longer, the better!

Step 5: Open the black water tank valve and dump the tank.

If nothing comes out, close the black water tank valve again and let Clear-It work for longer. Again, the more time you give Clear-It to work, the more successful the treatment will be.

For really severe clogs: You may need to use a PEX pipe to manually break up some of the waste to loosen it and allow the rest to flow out.

If liquid comes out, dump the black water tank.

Note:If you see good flow out of the discharge port that is suddenly interrupted, you may be experiencing a secondary clog. This occurs when only some of the waste and toilet paper is broken down and a large chunk creates another blockage. This is very common with compacted tanks.

In these instances, all you need to do is close the black tank valve, refill the black tank with water, and add another bottle of Clear-It. Wait an additional 72 hours to allow the waste to continue to break down.

Step 6: Close your black water tank valve again.

Step 7: Thoroughly rinse your black tank.

Rinsing well ensures all of the waste and toilet paper is broken up and out of the tank.

Do this by filling your black tank completely with fresh water, and then dumping. Do this twice, and your tank will be rinsed more thoroughly than when using sprayer wands, backflushers, or onboard tank rinsers.

Video:How to Rinse an RV Black Water Holding Tank

Guide:How to Rinse an RV Holding Tank

Step 8: Once you’ve cleared the blockage, close your black water tank valve again.

Keeping your black tank valve closed prevents pyramid plugs.

While it may seem logical to leave the black tank valve open to allow everything to naturally flush out, unfortunately, when you do this, all of the liquid will flow out as expected, but all of the physical waste and toilet paper tends to remain.

As the toilet continues to be used, the waste and toilet paper can stack on top of itself until the pyramid grows so large that it creates a clog by blocking off the pipe.

Learn More:What is an RV Pyramid Plug?

Step 9: Repeat the process if you think there may still be solid waste buildup on the floor of the tank.

And that’s it, these steps should have helped you fully clear a clogged black water holding tank, and allow you to enjoy clog-free camping once again.

Need Help Clearing Your Clogged RV Black Tank?

If you’ve completed all of the steps above and are still having trouble, please reach out to our amazing Customer Support Team. They will be thrilled to help you get your clogged RV holding tanks back on track.

RV Black Tank Cleaning Services

While the process to clear a compacted black water tank is simple, it does take time for the treatment to work. If time is an issue, then hiring a rv black tank cleaning service can dramatically reduce the time it takes to clear a clogged black water tank.

These services use specialized cleaning tools to do the job in a few hours, rather than in several days or weeks. For a no-fuss, time-saving option, companies often charge between $275-$500 for this type of service depending on the size and state of your holding tanks and your location.

Prevent Clogged RV Black Tanks With The Unique Method

To prevent camper clogs and wastewater issues before they happen, try implementing The Unique Method. Specifically created to help you enjoy problem-free holding tanks, this method has been developed over 30 years of solving RVers toughest wastewater problems.

While no process works like magic, following The Unique Method’s simple steps, and using the right products (bio-enzymatic formulas like Clear-It), can allow you to break down waste, eliminate odors, and prevent sensor probe problems all at once.

Take your RV travels to the next level with clog-free peace of mind thanks to Unique Camping + Marine.

Final Thoughts on Unclogging Compacted RV Black Water Tanks

Dealing with a compacted RV black water tank can sound scary, and can certainly put a damper on your upcoming camping trip. However, if you follow these easy steps, and let Unique Clear-It do the heavy lifting, you can be back on the road soon, and at a fraction of the cost compared to expensive tank cleaning services.

Drive into the sunset easily and problem-free with Clear-It, the world’s most effective, and strongest, tank unclogger.

For more advice about how to prevent RV clogs before they occur, review our guide about Preventing Clogs in Your RV Black Water Holding Tanks.