How to Unclog Your RV Black Tank 1090

It’s not a spot any RVer wants to be in – realizing you must unclog your RV black tank. Honestly, there’s a lot you can do to prevent this from happening, and these resources will help you learn how to avoid clogs in your RV’s septic system: 

What Causes RV Toilet Clogs?

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Photo by Camping World

Clogs happen. So let’s start with an overview of the types of RV toilet clogs: 

Issue #1: You left your tank valves open when connected to sewer hookups

Leaving tank valves open when connected to sewer hookups allows the liquids to drain out and leaves the solids behind, resulting in a dreaded “poop pyramid” in the bottom of your black tank.

Issue #2: You stored your RV without first dumping your black tank

Now you have compacted or hardened solids in the bottom of the tank. This can happen if you leave your tank valves open, but it’s a more significant issue for RVers that leave waste in their black tank when their RV is in storage. Liquids evaporate while solids dry out and harden.

Issue #3: You used your RV toilet improperly

Improper toilet use is the leading cause of clogs in the pipes leading to and from your RV black tank. By improper use, we mean using too much toilet paper, insufficient water, non-RV toilet paper, and flushing items other than TP and bowel movements. 

There’s no shame in not wanting to deal with a clogged RV septic system. Contact your local Camping World Service Center today to schedule an appointment to unclog your RV black tank. 

How to Know Your RV Toilet is Clogged

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Photo by Camping World

Two main signs tell you a clog is present in your RV’s septic system: 

  1. Nothing (or very little) drains from your black tank when you’re connected to sewer hookups and your black tank valve is open.
  2. You can’t clear the contents of your RV toilet bowl when flushing.  

Sometimes, your RV may exhibit both symptoms to tell you it’s time to unclog your black tank. Determining what caused an RV black tank clog can be tricky, but it helps to be honest about how well you’ve maintained your holding tanks. 

If you opened your tank valves for a week while connected to sewer hookups, you’re likely dealing with issue #1. 

If you forgot to empty holding tanks before winterizing your RV, you likely have a clog related to issue #2.

If you didn’t think using RV-friendly toilet paper was necessary, you’re probably dealing with issue #3

How to Unclog Your RV Black Tank

If you’re in one of these unfortunate positions, here’s how to unclog your RV black tank and return to enjoying your RV vacations. 

How to Unclog a “Poop Pyramid”

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Photo by Camping World

Start with the first four steps, but your path from there will differ depending on your results. 

  1. Close the black tank valve (and the valve for your gray water tank). 
  2. Pour an enzyme formula RV black tank treatment down your toilet. 
  3. Leave it in the tank according to the manufacturer’s recommendation (usually a few hours and up to several days). 
  4. Connect your sewer hose to a hookup and open the black tank valve. 

If waste flows out normally, close your sewer tank valve and fill the tank with water and additional waste digester to further break down solids. Leave for the recommended duration before emptying the black tank. 

If waste doesn’t flow, you’ll need to unclog your tank manually. This requires snaking your tank with a flexible RV tank wand. The best of these wands hook up to a freshwater source to have the same effect as an RV equipped with a black tank flush. 

To check that you’ve removed a clog, you’ll need to have your sewer hose connected and open your black tank valve. When waste flows out, add water to your black tank to flush it as thoroughly as possible. Repeat until clear water flows through your clear 90-degree elbow connector.

How to Remove Compacted Solids from your RV Black Tank

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Photo by Camping World

If you didn’t store your RV correctly after winterizing it, you’ll have to deal with a block of solids, not just a pyramid. Use these steps to remove compacted solids from your RV black tank: 

  1. Fill your black tank with fresh water and add an enzyme-digesting black tank treatment. 
  2. Let it sit in the tank as long as the treatment manufacturer recommends (usually at least overnight). 
  3. Take your RV to a dump station, connect your sewer hose, and try emptying the black tank. 

If no waste flows from your tank, close the valve and let the treatment sit for longer – another 24 hours won’t hurt. Repeat the process of trying to dump your tank. 

When the contents begin to drain from your tank, flush it completely. Then, fill the tank with fresh water again and drain until you no longer see bits of solids exiting your clear elbow connector. 

How to Clear Pipe Clogs in your RV

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Photo by Camping World

Unclogging a tank that has too much toilet paper or insufficient water is an easy fix. Things will be tougher if you flushed other hygiene products or didn’t use RV-friendly toilet paper

If nothing is draining out of your tank when you open the valve after leaving your valves closed, you’re probably dealing with a clog. 

Here’s your path to clearing clogged RV septic plumbing: 

  1. Use a plunger to try to remove the clog. It may only push out the blockage partially, but it can reduce the backup. 
  2. Try pouring an enzyme solution down the toilet and letting it sit for the recommended duration. After the time has elapsed, try flushing to see if the solution has eaten away at the clog. 
  3. If it doesn’t flush, try plunging the toilet again. You may need to add more tank treatment solution and wait longer. 

If that doesn’t remove the clog, use a flexible PEX pipe or your tank wand to push down through the clog and into the black tank. When you do clear the clog, fill your tank with fresh water and drain it completely to remove the clogged contents. 

FAQs About RV Black Tanks

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Photo by Camping World

To further help you prevent a clogged RV black tank, here’s more info to help you understand how to treat your RV septic water system right. 

How long can black water stay in an RV holding tank?

Your best solution – when your tank indicator LED hits two-thirds, empty it. We don’t recommend letting a full RV holding tank sit for more than a week without emptying it, as this will significantly increase the possibility of odors and clogs. 

Expert Tip: Avoid driving long distances with a full RV holding tank, as the bumps and vibrations can cause full and heavy black tanks to drop out of the bottom of your RV. 

What is the best RV black tank treatment?

When it comes to RV holding tank treatments, Thetford, Camco, Walex, and Pure Power (from Valterra) are some of the leading brands for odor elimination and waste digestion. Most of their products are designed for safe use in all RV septic systems but check the directions and labels before using them in your RV. 

Shop Camping World’s selection of sewer chemicals.

Can you put bleach in an RV black water tank?

Avoid using bleach when removing clogs from RV black tanks. Caustic chemicals can damage the seals, valves, and plumbing lines, leading to more extensive (and expensive) repairs. RV tank treatments are your best friend when you need to break down waste and unclog RV black tanks.


When you’ve dealt with a clogged black tank as an RV owner, you’ll know it’s much easier to avoid a clog than to fix one. Hopefully, these tips will help you eliminate your clog and get back to all the fun parts of RV living

Do you have additional questions about unclogging an RV black tank? Let us know in the comments below.

Tucker Ballister is our Technical Content Writer. He’s a lover of the open road and the proud owner of a 2021 Sunlite Classic travel trailer (his 3rd RV to date). Check out more of his RV adventures, gear reviews, and outdoor advice at thebackpackguide.com.
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