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Preventing Clogs In Your RV Holding Tank

  • 10 min read

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Article 7 of 8 in Series: RV Toilet Clogs

Read series from the beginning

Key Points: 

  • There are three types of camper clogs that could occur in your toilet or black tank: pyramid plug, compacted tank, blockage in the toilet line
  • Misreading sensors can sometimes fool you into thinking there is a toilet clog when there is not
  • Regularly practicing The Unique Method is the best way to avoid clogs

Clogged and stinky RV holding tanks and toilets are one of the leading issues RVers deal with every single year. These clogs and odors are frustrating and have the potential to turn travelers away from the RV lifestyle. The good news is that prevention of these issues is really simple. In this guide we are going to explore what kind of clogs could occur in your black water tank and what kind of habits you can adopt to prevent them. 

What Type of RV Toilet Clog Could Develop?

There are three types of clogs that could occur:

Diagram: RV Pyramid Plug | Unique Camping + Marine

1. Pyramid Plug – This is poop and toilet paper that accumulates into a pyramid shape right under your toilet line and has finally reached the top where it is now preventing anything from being added to the tank. A pyramid plug usually occurs when you have left your black tank valve open while on hook-up because any liquid added to the tank immediately drains out of the open valve allowing accumulated waste to dry and build up. Always leave your black valve closed unless actively dumping a full tank. For more details on pyramid plugs, refer to our guide, What is a Pyramid Plug?

Diagram: Compacted RV Tank | Unique Camping + Marine

2. Compacted Tank – A compacted tank just means that solid waste has accumulated in the bottom of your black water tank, preventing waste from exiting the tank when the valve is opened. This can occur if you are not using enough water in your tank, not using a high-quality waste-digesting treatment, have a leaky discharge valve, or waste was left sitting in your tanks while in storage, which means the liquids eventually evaporate and the poop dries out, making it much harder to clean when you’re ready to use it again.

Diagram: Blocked RV Toilet Line | Unique Camping + Marine

3. Blocked Toilet Line – A blockage of toilet paper and solid waste can become trapped in the actual pipe that leads from the toilet bowl to the black tank. This problem mostly occurs in RVs where the toilet is not situated directly over the black tank and the plumbing system therefore has turns and elbows where waste and TP can easily become congested. With systems like these where the toilet pipe does not empty vertically into the tank, it's best to use more water than you may think necessary when flushing. This type of clog shares the same symptom as a pyramid plug but has a slightly different fix, so be sure you know exactly which type of issue you are dealing with.

Diagram: Misreading Sensor Probes | Unique Camping + Marine

Note: Misreading sensors that are caked with waste and toilet paper debris (black water tanks) or grease and oils (gray water tanks) can sometimes falsely indicate you have a clog, telling you the tank is full but nothing comes out when you open the black valve. It could be a compacted tank or it could just be an empty tank that has sensors falsely reading full. If all you have is misreading sensors, it is an easy fix. Refer to our guide on How to Clean and Restore RV Holding Tank Sensors.

In the next section, we will cover some of the primary Unique Method habits that you can practice to avoid clogs before they ever develop. Of course, the most thorough way to do this is to follow The Unique Method, so we urge you to become very familiar with that guide as well.

How to Prevent Camper Clogs

The best way to prevent any type of clog is to follow The Unique Method, which is our proven process for treating RV wastewater tanks. The Unique Method is a 50/50 approach that requires 50 percent the right care habits and 50 percent the right products. We always recommend our products when using this proven process because they were formulated with The Unique Method in mind, which means you get the best possible results.

In the sub-sections below, we will call out a few of the techniques to prevent specific types of camper clogs, all of which are included in The Unique Method, so we highly recommend that you begin using the process as a preventative measure against issues like clogs.

Keep your black tank valve closed unless actively dumping a full tank


One of the biggest misnomers in the RVing world is that you can leave your black tank valve open while on hook-ups and everything will just flow right into the sewer. Doing this is the fastest way to develop a clog. When you leave your black tank valve open, any liquid inside your holding tank drains out and all that you're left with is a pile of solid waste that keeps getting taller every time you go number two. Liquid (specifically water) helps break down the waste and cover the odors, but without it, you may end up with a pyramid plug, which is literally a pyramid-shaped pile of waste that reaches right up to the toilet line. A pyramid plug will build until it finally stops anything (even liquid) from being added to the tank. Many people don't realize that their black water tank is most likely flat across the bottom, so if solid waste is added to a tank devoid of liquid, it simply lands on the bottom of the tank and continues piling up in that one spot.

Caution: You might be one of those campers who always leaves your black tank valve open and you've never experienced any problems. You’re lucky you haven’t experienced one so far and conversations with hundreds of RVers dealing with clogs tells us that it’s only a matter of time before your luck runs out. We strongly recommend that you change this practice while you're still ahead!

Guide: Why It's Crucial to Keep Your RV Black Water Valve Closed

Use a high-quality, bacteria-based tank treatment (like Unique RV Digest-It Plus)

You want the waste inside your black water tank to be nearly liquefied and the best way to accomplish that is to regularly use a high-quality bacteria-based holding tank treatment, like Unique RV Digest-It Plus. Bacteria-based products work amazingly well because aerobic bacteria (the kind in RV Digest-It Plus) break down waste into near liquid form without leaving behind residue and byproducts, without adding odors, and in fact, push out the smelly bacteria that ride in on the solid waste.

There are other holding tank treatment products available, but again, we highly recommend you take the bacterial route simply because it is so effective at keeping your tanks clean and fresh. And if you’re going to use bacteria-based tank treatments, be sure to keep your black valve closed until you’re ready to dump a full tank. If you leave the valve open while on hook-ups, your tank treatment will simply flow down to the sewer and it will be just like you didn’t add any treatment at all.

Guide: Why You Should Use a High-Quality Waste Digester in Your RV

Avoid using chemical cleaners and antibacterial dish and hand soap

If you opt to use bacteria-based tank treatments, using chemical toilet bowl cleaners, shower cleaners, or antibacterial dish soap and hand soap will counteract the tank treatment you are using. These products will kill the beneficial, waste-digesting bacteria you’ve added to your tank through a bacteria-based treatment like Unique RV Digest-It Plus. If you damage or kill this bacteria by using chemical cleaners, it can easily lead to clogs because waste remains solid instead of being broken down into its smallest possible size by the bacteria. Chemical cleaners can also damage seals and valves, so do your homework before using them in your RV.

Guide: Why Are Bacteria and Enzymes Good for Your RV Holding Tanks?

Use lots of water each time you flush

Water is one of the best things you can put in your wastewater tanks. In fact, even if you don’t use any tank treatment, being generous with water in your black tank will still help prevent a pyramid plug and a compacted tank because water helps soften the waste so it dips below the water line and doesn’t cling to the walls and floor of the tank. The easiest way to add water to your tank is to simply hold down the flush pedal for at least 10 seconds every time you flush. This adds more water to the tank to help control odors and helps keep the bacteria healthy and doing their job well. 

You should also add water to the toilet bowl before you use it and replenish the bowl with water after every flush. This helps with continuous odor prevention and a smooth trip for the waste to get to the tank and avoid a toilet line blockage. Water is also super important for the aerobic bacteria you add to the tank by using a bacteria-based tank treatment; they need lots of water to survive and to reach all the waste they will break down.

You might think dry campers/boondockers are the ones who deal with the issue of pyramid plugs the most because they don’t use much water, but the difference is they MUST keep their black valve closed because it is considered illegal dumping to empty your black water tank onto public use lands (and just about anywhere other than approved dump stations or your own home clean out valve); therefore, any liquid, even if it’s a small amount, still remains inside the tank. It’s actually hook-up campers who deal the most with pyramid plugs because they often leave their black valves open, which will allow all the water to leave the tank and the solid waste to dry out and accumulate in one place. Always keep your black valve closed unless actively dumping a full tank; we sound a little naggy about keeping your black valve closed, but it’s less annoying than experiencing a clog!

Guide: Why Using Lots of Water in your RV Toilet and Tanks is Crucial

Keep temperatures regulated

Odors will increase in hot temperatures, and if you are using a bacteria-based tank treatment, high heat will cause the bacteria to be super sluggish and not digest waste effectively. All high-quality bacteria-based holding tank products have an effective temperature range of roughly 45-85 degrees Fahrenheit. On both the extreme cold and the extreme hot ends of that spectrum, all brands of bacteria-based holding tank treatments will struggle. If you’re camping in either of these environments, we recommend insulating or heating your tank in cold weather and increasing water usage and adding a higher dosage of bacteria treatments in hot weather.

Guide: How to Keep Your RV Holding Tanks from Freezing

Guide: Controlling RV Holding Tank Smells in High Heat

Rinse/flush the tank (even briefly) after each dump

The wastewater tanks use gravity to dump, meaning there will be residual waste particles stuck to the walls as the waterline slowly decreases. Think about a sink dirty dishwater draining; yes, most of the residual food particles go down the drain, but there are always some grease and particles that figure out how to cling to the edges of the sink. It’s the same with even small particles of waste clinging to the tank floor, walls and sensors; if you’re not rinsing every time you dump, small bits of waste could accumulate after each dump and then cause sensor misreading and residual waste buildup on the tank floor and around the discharge port.

Every time you dump your tank, flush or rinse it well. The longer you rinse your tank, the better (we recommend 20-30 minutes of rinsing when possible); this will help to clean out the nooks and crannies of the tank. This thorough cleaning will ensure that no residual debris is hiding somewhere in the tank waiting to create a future clog.

Guide: How to Flush Your RV Holding Tank

Perform a regular deep cleaning

Deep cleaning your tanks will help wipe the tank and the sensors of even minimal waste residual that could be clinging to them. We recommend weekend warriors and dry campers/boondockers do this at the start and end of each camping season and full-time RVers should deep clean every 3-5 dumps. Luckily, deep cleaning is fairly simple, even for the full-time RVer who still needs to use the tanks. 

Guide: Deep Cleaning RV Wastewater Holding Tanks

Never store your RV with waste in the tank

Storing your RV with waste in the tank is the best way to create a compacted tank. You may have done everything right to keep the waste liquefied, but if you store the RV with waste sitting for weeks, the water in that sloshy waste mixture will eventually evaporate and all that will be left is a nice, even layer of dried out waste that will cover your discharge line, making it impossible to dump later. The best policy is to dump at a station on your way home or immediately when you return home so you don’t forget about it and have to deal with a compacted tank later.

Guide: How to Prepare Your RV Holding Tanks for Storage


The best way to prevent camper clogs is to always follow The Unique Method; all of the habits we’ve described in this guide are included in The Unique Method, plus a few more that will benefit your camping experience. Here is a short summary of the prevention measures we discussed in this guide:

  • Keep your black tank valve closed unless actively dumping a full tank
  • Use a high-quality, bacteria-based tank treatment
  • Avoid using chemical toilet/shower cleaners and antibacterial soap
  • Use lots of water every time you flush the toilet
  • Keep tank temperatures between 45 and 85 degrees Fahrenheit
  • Flush the tank after every dump
  • Perform a deep cleaning at least twice a year
  • Never store your RV with waste in the black tank

Now that you know what types of habits you should be applying to keep your tanks problem-free, you might wonder, “Should I just not poop in my RV toilet to avoid clogs?” Some in the RVing community have decided to not poop in their RV toilet in order to curb the possibility of clogs, but don’t forget why you bought your RV: to enjoy the comforts of home on the road or in the wilderness. Read our next article to find out why it is more than okay to poop in your RV toilet.

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