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Unclogging An RV Toilet

October 11, 2019

How to unclog a plugged camper toilet RV motorhome holding tank step by step

So you have a clogged RV toilet. Well, you’re not alone! Plenty of RVers have been in the same boat. In truth, nothing kills RVing fun like a disgusting, backed-up toilet! Let's be honest: isn't a comfortable bathroom experience one of the main reasons why we buy RVs? There are a number of reasons your toilet might be clogged or appear clogged: 1) a pyramid plug, 2) a compacted tank, or 3) misreading sensors. If you want to get rid of your clog, no matter what the cause, read on. We'll tell you everything you need to know to find a solution. Don't worry. In most cases, this is a very inexpensive and easy fix!

What’s covered in this guide:

  • How to diagnose your problem.
  • What’s causing these problems.
  • How to unclog your RV holding tank if you have a pyramid plug.
  • How to unclog your tank if you have a compacted tank.
  • How to restore your misreading sensors.
  • How to prevent pyramid plugs.
  • How to prevent a compacted tank.
  • How to prevent misreading sensors.

Step 1: Diagnose Your Problem

The first phase of unclogging your RV holding tank is to diagnose the problem! There are a number of reasons your RV toilet might be clogged or appear to be clogged: 

  1. A pyramid plug
  2. A compacted tank
  3. Misreading sensors

To determine which issue you’re dealing with, here’s what to do:

  • Try opening your black tank valve. If nothing comes out, your tank is either empty, or you have a plug. In this case, you do not have misreading sensors. 
  • Try to add water to your black tank through your toilet. If you can add water, then you do not have a pyramid plug. 
  • If you can add water to your tank, but nothing comes out when you open your black tank valve, then you have a compacted tank. A compacted tank prevents added water from exiting the system, but it doesn’t prevent it from being added. 
  • If you can’t add water to your tank because a mound of poop is blocking your toilet, then you have a pyramid plug. A pyramid plug blocks you from adding any water to your tank through the toilet. 
  • If you can add water to your tank and water comes out when you open your black tank valve, then you do not have a clog at all. In this case, your sensors are misreading and need to be cleaned (see below).

What’s Causing These Issues?

Pyramid Plugs

The majority of clogged RV toilets come from pyramid plugs. A pyramid plug is literally a pile of poop and toilet paper that has built up from the bottom of your black water holding tank and formed a pyramid of grossness that has now reached your toilet and is clogging it up. When dealing with a clogged RV toilet, many people incorrectly assume that their holding tank is totally full. For a very few people, this may indeed be the case, but for most people, the culprit is not a completely clogged tank but, in fact, a pyramid of waste.

To understand why you get a pyramid plug, you first have to understand that your holding tank is essentially flat on the bottom. Why is this important? Well, most people who get pyramid plugs do not follow Rule #1 of The Unique Method: KEEP YOUR BLACK TANK VALVE CLOSED. This is an important point, because if you follow The Unique Method, most of these issues would have been prevented in the first place (see below)!

Here’s how a pyramid plug develops:

When your black water tank valve is kept in the closed position during normal operation, the solid and liquid waste accumulate in your tank and slosh around. When you dump, all of that sloshing waste flows out smoothly.

However, if you keep your black water valve in the open position during normal operation (which you shouldn’t!), every time you use the toilet, the liquid waste flows freely out of the tank and into the sewer, but because your tank is flat on the bottom, the solid waste accumulates. Over time, if you keep adding more and more of that solid waste, you will begin to build a pyramid plug.

Compacted Tanks

A compacted tank is less common than a pyramid plug but no less frustrating! There are a couple ways that a compacted tank could develop: 1) you could have solid waste or toilet paper stuck in your discharge line or 2) you didn’t dump your tank before storing your RV. 

The first way a compacted tank might develop is if solid waste or toilet paper clogs your discharge line (the line leading from your black tank out of your RV), your discharge port, or the tank drain. If these lines are blocked, the waste has nowhere to go, so it builds up on the bottom of your tank. 

The second reason you might have a compacted tank is because you did not dump your tank before putting it in storage! This by far is the worst way to develop a compacted tank. When you put your RV into storage without first dumping your tanks, all the water inside the tank evaporates, leaving the hard, dried solids behind. This will clog your discharge line and become extremely solid. But, lucky for you, our products will still remove it (see recommendations below)!

Misreading Sensors

Misreading sensors are a common problem for RVers, and many accidentally mistake them for a clogged tank.

Note: Misreading sensors are not limited to black tanks. They can develop in gray tanks as well. (Read our article on restoring gray tank sensors by touching or clicking here)

Misreading tank sensors in your black tank are caused by poop and toilet paper that coat the surface of your sensor probes. These sensors typically work by completing an electrical circuit once the water inside the tank reaches the level of the sensors. But when poop and toilet paper cake onto the surface of your sensors, they complete the electrical circuit, which causes your sensors to read “full” when your tank is actually empty or only partially filled.

Step 2 - Fix These Problems

Pyramid Plug

If you have a pyramid plug, you won’t be able to add much if any water to your tank through the toilet (because it’s clogged with poop!). All the same, some liquid will often get through even if it’s only a tiny bit. So, before you try anything else, we recommend that you open the toilet valve and pour 1 entire bottle of Unique Tank Cleaner into your RV toilet bowl. Some product will likely seep through the top of the pyramid plug and open a channel into your tank. If you can get this to happen, pour as much water into the tank as you can. (Remember to keep your black tank valve closed, otherwise this water will all flow out again!) 

Sometimes, however, the recommendations given above won’t cut it. You still won’t be able to get water into your tank. In this case, we recommend that you go down to the hardware store and purchase some PEX pipe. PEX pipe is more flexible than PVC, which will allow you to access areas that you wouldn’t be able to access with a pipe that won’t bend. 

The idea is to use a flexible PEX pipe to break up the top of the pyramid plug, creating enough space to get water into the tank. Here’s how to do it: first, turn off your fresh water. This will allow you to hold your toilet flush pedal down and keep the valve open without filling your toilet with water. With your toilet valve open, send your length of PEX piping down the toilet and into the tank. Try to knock out some of the pyramid plug with the PEX pipe or at least create enough space to get some water and Tank Cleaner into the tank. 

If you can create enough space to add water, pour 1 entire bottle of Tank Cleaner into your tank through your toilet and add as much water as possible. Let the product work for as long as you can. There is no time that is too long for Tank Cleaner to do its job. It won’t harm your tank, and the longer you give it, the more it will digest the waste making up your pyramid plug. 

Note: If your tank is so full that you cannot add any more water, you can skip adding water to the tank. However, you should know that for Unique Tank Cleaner to work properly, it needs liquid to nourish the active cultures that digest the waste. So, getting as much water in the tank as possible is incredibly beneficial.

Open your black tank valve and dump your tank. If you have a tank rinser or flusher, you should rinse your tank for 20-30 minutes. It’s important to run your tank rinser for 20 minutes or more after the tank contents have been broken up and successfully dumped from your black water tank. Often, when you first start your rinser, you'll see clear water coming out, but don’t assume that your tank is completely clean. This is just the clean hose water running out of the tank. Normally you’ll find that if you let the rinser run longer, at some point the waste will break loose, and you'll see a tidal wave of brown water come pouring out of your tank. This can often last for several minutes!

Close your black tank valve and keep it closed so you don’t get another pyramid plug! Also, you may need to repeat the process given above a few times to make sure the tank is completely clean. 

Here’s a quick summary of the steps given above:

  1. CLOSE YOUR BLACK TANK VALVE. (Always keep it closed unless you’re dumping your tank.)
  2. If the plug isn’t blocking your toilet opening, add several gallons of water to your black tank. The more water, the better, so fill up your holding tank as much as possible without making a mess. Again, using Tank Cleaner and PEX pipe can help to unblock the toilet opening. 
  3. Through your RVs toilet, pour an entire bottle of Unique Holding Tank Cleaner into the tank (if possible).
  4. Let sit for as long as possible. After the treatment period, the solids in your holding tank should be broken up and liquefied.
  5. Open your black tank valve and dump the tank.
  6. If you have a tank rinser (i.e., the flusher), run it for about 20-30 minutes so that the tank is thoroughly rinsed out.
  7. CLOSE YOUR BLACK TANK VALVE, and only open it when you're dumping so you never have to deal with this problem again!

If you’ve tried all the recommendations given above, and you still aren’t seeing results, please reach out to our customer support team!

Compacted Tank

A compacted tank is a little easier to fix because your toilet opening isn’t blocked, so it’s easy to add water and Tank Cleaner to your black tank! With that said, sometimes the compacted waste on the bottom of the tank can be extremely solid (especially if it has been allowed to dry while the RV was in storage). 

As you might have guessed, the first step in fixing a compacted tank is to close your black tank valve and fill your tank with water. Next, pour 1 entire bottle of Tank Cleaner into the tank through your toilet. Let sit for as long as possible. Open your black tank and allow the tank to empty out. Flush your tank with a rinser or flusher for 20-30 minutes.

All the waste should be liquified when you open your tank, but if nothing comes out or you only get a small amount of waste to exit the tank, close the valve and let the product sit a little longer. When you’re dealing with a compacted tank, you will probably have to let Tank Cleaner work a little longer than normal. This is due to the fact that the compacted waste is so solid and, well, compacted!

Pro tip: If you’re having issues getting your tank to empty after you open your black tank valve, it can sometimes help to (very gently!) tap your discharge pipe with a shoe or other object. This can help to dislodge any chunks of waste stuck in the pipe or discharge port. Again, just as a caution, be sure not to hit the pipe too hard. You don’t want to break it! Also, using PEX pipe to dislodge chunks of waste in your discharge port or pipe might also work. 

Here’s a summary of the points given above:

  1. CLOSE YOUR BLACK TANK VALVE. (Always keep it closed unless you’re dumping your tank).
  2. Fill the tank with water.
  3. Pour 1 entire bottle of Unique Holding Tank Cleaner into the tank through your RV toilet. 
  4. Let sit for as long as possible. After the treatment period, the waste inside your black tank should be liquified.
  5. Open your black tank valve and dump your tank.
  6. Run your tank rinser or flusher for 20-30 minutes.
  7. If the tank won’t empty, let Tank Cleaner work for a little longer. You can use a shoe to gently tap the discharge pipe, which may help to dislodge some chunks of waste.

If you’re still having issues after following all the steps above, please contact us here!

Misreading Sensors

Like we said above, some people mistake misreading sensors for a clogged tank, but remember, if you can pour water into your tank and dump it out of your discharge port, then you don’t have a clog. In this case, you’re dealing with misreading sensors that are telling you your tank is full when in fact it isn’t. 

Our comprehensive guide to cleaning and restoring holding tank sensors will walk you through each step of restoring your black tank sensors. Keep in mind, however, that if you follow the processes given in the guide, and you still have issues, your sensors might simply be broken. If that’s the case, you’ll just need to replace them. 

Step 3: Prevent These Problems

Pyramid Plugs

Like we mentioned earlier, your holding tank is flat on the bottom, which can cause waste to accumulate into a giant pyramid in your tank if you don’t keep your black tank valve closed. So the key to preventing pyramid plugs is to always follow rule #1 of The Unique Method: ALWAYS KEEP YOUR BLACK TANK VALVE CLOSED unless you’re dumping your tank, which we have admittedly harped on quite a bit in this article! 

But it’s a crucial point, because following The Unique Method will virtually eliminate all holding tank clogs and odors, and when it comes to pyramid plugs, keeping your black tank valve closed is the first step.

The idea is to ensure that the liquid inside your tank is a sloshy mixture. (You want it to slosh around in your tank, which will help keep the waste liquified.) You also want to make sure you’re using a high-quality, waste digesting, bacterial holding tank treatment like RV Digest-It.  All this is covered in depth in The Unique Method. The Unique Method is a series of practices that we have created through our own experience and working with thousands of RVers over the years. Try it out and tell us what you think! We've found that it can be a lot to grasp at first, but is absolutely worth it to keep your RV clog AND odor free!

You might think that a lot of people experience clogged toilets when dry camping (boondocking) because they use very little water with each flush, but in most cases, dry campers have to keep their black tank valve closed until they get to a dump station. This allows for plenty of sloshy action inside the tank that can help keep the waste liquefied, so clogs aren’t as common for dry campers as they are for full hook-up campers.

We know, we sound like a broken record, but we cannot stress it enough: keep your black tank valve closed! As much as we like to think of our RVs as our homes, the plumbing simply doesn't work the same way as the plumbing in your home, so you can't expect your waste to flow out into the sewer lines with every flush.

Compacted Tanks

To prevent a compacted tank, first make sure that your black tank valve is closed and you’re using plenty of water in your tank. In general, the more water you use, the less likely it is that you’ll experience clogs or odors.

On top of adding a lot of water to your tank, you should also be using a high quality waste digesting treatment like RV Digest-It. A waste digesting treatment will add good bacteria to your tank, which will help to break down the solid waste.

Finally, never store your RV without first dumping all the waste and flushing out your tank! This is a simple but absolutely critical point. It’s worth going through the extra effort to dump and clean your tank before you store it so that you don’t have to deal with these time-devouring and frustrating issues down the road!

And last of all, like we said above, follow The Unique Method to make sure you never have to deal with this issue again! 

Misreading Sensors

Misreading sensors can be easily restored by performing an annual deep clean of your tank using Unique Sensor Cleaner. Again, this is covered in The Unique Method as well as in our article on cleaning and restoring holding tank sensors!


We hope that this article answers all of your questions about your clogged RV toilet! If after following all the guidelines above, you should still find yourself in this putridly poopy predicament and need further assistance, please don't hesitate to reach out to us for help. We're more than happy to help you get your toilet issues back on track!

Happy Camping!

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