How To Unclog Your RV Black Tank

Contributor

Tucker Ballister

Favorite Trip

5 Months Solo on the Road

Home Base

Hendersonville, NC

Favorite RV

2008 Fleetwood Bounder

About Contributor

Tucker Ballister is our Content Strategist. 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.

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.

  • Comment (10)
  • Brian Lasley says:

    Is restore-it black tank sensor cleaner good to use in a 2023 Jayco J Flight Baja trailer

  • Ryan Watkins says:

    My problem is I can add water through the flush connection, pull the valve to flush it and. quite a bit comes out. But there is waste in the top half and the toilet fills up quickly with water just below the flushing foot pedal lever. I’ve snaked it from the top half once and it seemed to work but now it is backing up in the top half again. The top half won’t drain, what’s the deal?

    • Hi Ryan,

      Sorry for the delayed reply. I wanted to reach out to our technical service team to get their insights. I’d start by referencing our article on maintaining RV holding tanks, which has some great information on preventing back ups and odors: https://blog.campingworld.com/learn-to-rv/maintain-rvs-holding-tanks/

      Beyond that, you mention running water through the flush inlet and THEN opening the drain valve. Your tank flush won’t work as intended if the tank has water in it since the standing water blocks the spray head stream from hitting the solids that have accumulated. You also run a huge risk of flooding the RV with waste water or even blowing the toilet off of the floor!

      The tank flush should only be used when the RV is connected to the dump station with the dump valve open. A clear plastic adapter between the termination outlet and the sewer hose will allow you to observe the discharge water for debris so the know when the tank is clean. The tank should ideally be flushed every single time it is dumped. Now that you have a blockage, it will require significant effort to restore full function.

      I recommend beginning with a full quart of name brand Aqua Chem for every 20 gallons of tank capacity and fill it to the top with water (hot if possible). Let stand 24 to 48 hours. Dump the tank and use the tank flush and/or a hand wand for up to 2 hours. You can use a flashlight or a snake camera down the toilet to see if all of the debris has been evacuated. If not, you can add ¼ to ½ a tank of water and several large bags of ice to the tank and another quart of chemical. Immediately drive around, starting, stopping and turning as much as possible so the ice can scour the remaining solids from the tank. Let sit another 24 to 48 hours before dumping and flushing again.

      It is possible that even after fully cleaning the tank out to see the monitor read incorrectly. This is usually due to the corrosion damage to the in tank sensors. They will have to be replaced with new at a Camping World Service Center.

      Here’s our link to proper use of your RV’s black tank flush as well: https://blog.campingworld.com/learn-to-rv/how-to-use-an-rv-black-tank-flush/

      And one more to where you can find the service center closest to you if you want our certified technicians to have a look at your system: https://rv.campingworld.com/rv-service-maintenance#js-anchor-locations

  • Carlie says:

    We went to drain our tank tonight and we’re not sure if there’s a “poop pyramid” built or the gate is stuck. The sensor is also not working it says the tank is empty and we are positive that is untrue. How do we figure out the solution? What should we do first?

    • Hi Carlie!

      The worst case is that you have a clog or a stuck gate. I’d begin by adding a tank treatment (https://www.campingworld.com/maintain-rv/sewer/sewer-chemicals) to your black tank to expedite the breakdown of any solid waste therein. But there could be several other things going on, depending on the exact process you’ve used.

      I’ll share that one of the most bonehead moves I’ve made is leaving the storage caps on my sewer hose. These caps (https://www.campingworld.com/camco-sewer-hose-storage-caps-for-lug-bayonet-fittings-104644.html) won’t allow you to drain your tanks, obviously. So, you can also close your tank’s gate valves and ensure these caps are removed from both ends of your sewer hose.

      If that’s not a variable in question, I’d have a couple follow up questions:

      Is your RV equipped with a black tank flush you can use to try to clean out the holding tank? If so, here’s our tutorial on using that black tank flush: https://blog.campingworld.com/learn-to-rv/how-to-use-an-rv-black-tank-flush/

      Do you have a tank wand on hand? (https://www.campingworld.com/flexible-tank-wand-14497.html) This can be connected to a garden hose to effectively serve the same purpose as a black tank flush. Just ensure your sewer hose is connected and the gate valve is open before using a tank wand.

      Have you attempted to add water to your toilet? Is there anything cautioning you against doing so?
      Adding water can help get things moving, but, again, ensure your sewer hose is attached and the gate valve is open before doing so.

      Checking the gate valve itself is a scary proposition, as you can probably imagine. If you detach your sewer hose to visually check whether the valve is opening when you pull the handle out…well, you know what might happen. So if the above solutions don’t work for you, I’d highly recommend contacting one of our service centers: https://rv.campingworld.com/rv-service-maintenance

      Hopefully, adding a tank treatment can break down solid waste and allow you to empty your tank. Follow the instructions on that package for how long to let that treatment work before attempting to empty your tank.

      And don’t hesitate to let us know if you have any follow-up questions!

  • Brenda Rippy says:

    Before leaving the campground, we empty our Black/Gray water tanks. But the inside readers show the black water still 2/3 Full while the gray water shows empty. What are we doing wrong?

  • Lakin Zoe says:

    I read your entire content re the black tank directions, problems, different options and prevention methods. The drain snake will be a piece of reasonably inexpensive equipment to help clear a clogged RV toilet.

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