How to unclog an RV toilet holding tank

How to unclog an RV toilet holding tank

Having a clogged RV toilet holding tank is the most worrisome and disgusting circumstance you would ever pray for. The thought of having a backed-up toilet that can’t be flushed makes some people’s hearts sickened. However, if you are in this condition you don’t have to panic because there are many ways to unclog your toilet tank and continue enjoying your toilet tank.

Nothing kills the enjoyment of your RV toilet more than having a clogged or backed-up toilet, but with the few techniques I will analyze, you will kiss goodbye to a clogged toilet tank. To start with the first thing is to be sure whether you have a clogged toilet or not.


Clogged Toilet Issues 

If you have a clogged toilet, it’s important to check and know what causes it, before looking into how to unclog it. You don’t want to jump into finding a solution and later end up in the same situation since you don’t know what causes it. Here are some of the causative factors of clogged toilet holding tanks:

  • Pyramid plug
  • Blockage in the line
  • Compacted waste
  • Sensors misreading

How to diagnose the causes of your toilet clog

The first phase is to diagnose whether you have a toilet clog or not.

To diagnose pyramid plug

Start by opening your toilet holding tank, if nothing comes out, you probably have a clog but this is how you know, flush your toilet, if water goes down into the tank, you do not have a toilet clog, however, if the water backed up into the toilet bowl or doesn’t go smoothly, you probably have a pyramid plug or blockage in the line between the toilet and holding tank. 

If you are the type that does leave your toilet tank open you will likely have a pyramid plug but if you do close it and still experience a clog that should be a blockage in the line.

To diagnose a blockage in the line

Most people confuse this with a pyramid plug, however, there’s a difference and it lies in whether you open your tank valve or close it. A tank valve should be closed all the time except if you are dumping the tank.

To diagnose a compact waste

This is not too complex to check. You perform the same process you did in the diagnosis of pyramid clog, open the tank valve and check its rate of flow when flush, and do the same thing when closed. If water flows to the tank, then you probably don’t have an RV toilet clog. However, the things you are seeing may be from sensors misreading which makes you think there is an accumulation of compacted waste.

To diagnose sensor misreading

In some cases, sensor misreading can make you think you have a clog on your toilet holding tank. However, the best way to know is to pour water into your tank, if the water comes out with no hindrances. It might be faults from the sensor misreading.

Causes of RV toilet holding tank

Pyramid plug

Most clogged RV toilet comes from a pyramid plug. This is a situation where a pile of poops and toilet paper that had built up from the bottom of the toilet holding tank then forms a pyramid of grossness that moves upward and prevents the entry of water and particles. This doesn’t mean your toilet tank is full like some RVer think, however, the problem is the clogged tank which arises from the accumulation of waste.

When you close your tanks, all liquid and solid waste flows to the bottom and slosh around. But when you dump it, everything flows out smoothly. When you open the tank valve during normal operation the liquid flows out leaving the solid accumulating on the bottom, this build-up forms a pyramid plug.

Blockage in the line

When you have a blockage, waste (most commonly toilet paper) has accumulated in the pipe that connects your toilet to your holding tank, which is why water is backing up into your toilet bowl. In RVs where the toilet is farther from the holding tank, a clog in the line usually occurs. 

While the majority of recreational vehicles have toilet lines that drop straight down into the black tank, others have long lines with elbows. Toilet paper typically accumulates and causes clogs at these elbows.

When toilet holding tanks have a pyramid plug, many folks believe they have a blocked line, this is because both present the same signs as water won’t flow down when flushed.

Compacted waste

Compacted waste is not that common among all the causes. It develops mainly when solid waste accumulates in the holding tank and prevents the tank from dumping properly. This occurs when you are not using an effective waste-digesting treatment or not following the right treatment process. 

This can also occur if you didn’t empty your tank before putting your RV in storage and the waste has dried out and solidified into a brick. This is by far the worst method for creating a packed tank. The water within the tank evaporates when your RV is put into storage without first emptying the tanks, leaving the dry, hard sediments behind. Your discharge line will get highly solid and clogged with this.

Sensors misreading

Sensors misreading is a common cause of clogs in RV toilets. Poop and toilet paper that cover the sensor probes in your black tank might cause them to misread tank sensors. When the level of the water within the tank reaches the sensors, an electrical circuit is normally closed by these sensors. 

However, when feces and toilet paper build up on the surface of your sensors, they complete the electrical circuit and make them register “full” even though your tank is empty or only half filled.

How to unclog an RV toilet holding tank

How to unclog an RV toilet holding tank

Unclogging an RV toilet holding tank doesn’t have to give you a headache when there are quite a several methods that can be employed to wave goodbye to clogging issues. The four common methods include:

  • Use of hose
  • Hot water method
  • Use of special tools
  • RV tank clog cleaning solution.

Before looking into the step-by-step process of applying this method, some materials must be available before this method can be used. They include:

Method 1: Use of hose

You need gloves to protect your hands from splattering waste or debris, a disposable glove is highly recommended. An important material you will need is a water hose to provide enough pressure to flush away the cause of the clog. Note that, the water hose you use can’t be used in refilling the water tank again, so it’s advisable you use an old water hose.

Method 2: Hot water method

Boiling water is the only thing you will need here. Try to prepare at least a gallon of boiled water or more.

Method 3: Use of special tools

Here there are like three special tools you will need in this method. The first is the toilet plunger, used best in removing minor clogs. The pull and push action of these tools works effectively in unclogging RV toilet tanks. 

The second is the Drain snake for removing hard and stubborn clogs. You can buy an Omont 4-pack drain snake. It works well. A drain pipe is also effective for curved/angled toilet pipes that are susceptible to clogging. 

The last is a bucket, anyone will use either plastic or metal, but the size matters, it must be more than the capacity of the holding tank.

Method 4: RV tank cleaning solution

All you need here is the RV tank clog cleaning solution and a glove. However, avoid the one that has high bleaching power because of your RV’s plastic pipe.

Step-by-step process

Method 1: Use of water hose

Start by connecting one end of your hose to a water source- this is mainly for a power flush. Position the hose down the toilet and set the water pressure from moderate to high. You can connect the water hose to a compressor to increase the pressure.

Spray the water where the clog is located. In some scenarios, the pressure of the water could be high hence disintegrating buildup and transfer into the sewer hose. This is a relatively easy task.

Method 2: Hot water method

With your boiling water, you can unclog an RV toilet holding tank, however, it requires patience for the clog to dissolve. Ensure you use your nose cover too because of the stinking odor.

Step 1: Boil the water either on a stove or water heater. Use a large pot to save you the stress of boiling the water in batches. Note that, it’s wrong to pour the boiled water straight into the toilet because it can damage the PVC piping and seal. Therefore, set the boiled water apart for some minutes before using it.

Step 2: The next thing is to turn off the water main. Open the toilet valve while waiting for the water to cool a bit.

Step 3: Now fill the blocked toilet with hot water. To clear the blockage, leave the hot water in the sink for several hours or overnight.

If there are any blockages, this should clear them, but if you want to boost its efficacy, repeat the process in the morning. Flush the toilet after letting the hot water stand for a few hours.

Method 3: Use of special tools

If the use of hot water doesn’t seem to solve the problem. You can try using special tools to unclog your toilet holding tank. Follow this procedure:

Step 1: The first thing is to prepare for unclogging by ensuring no liquid drips from the tank. Place a large bucket under the dump pipe in place of a catch basin for any escaping liquid. Ensure the dump valve remains open as you remove the sewer hose from the camper van.  

Step 2: You can use a toilet plunger if it is a minor blockage. Drive the plunger into the toilet tank, and push the plunger in and out until you find and remove the clogs. If this isn’t effective enough you can use the third approach.

Step 3: use the drain snakes

Slide the drain snake through the plumbing by inserting it into the dump pipe. Hook it into the clogged debris once it encounters a blockage and twists it. Twist the object until you feel the debris fragment and enter the holding tank.

As soon as you notice any liquid leaking from the pipe, remove the snake and ask someone to stop the valve. Reconnect the sewage hose after that, then empty the tank as usual.

Method 4: RV tank clog solution

The best method of unclogging stubborn toilet clogs is the use of chemicals (tank clog solution). It is easier and faster if applied rightly.

If you use a tablet holding tank solution, you only need to drop a few tablets into the holding tank. Allow it to sit for a few hours or as directed by the label.

Use the entire container of cleaning solution for the liquid version. Don’t activate the cleaning agent for up to 27 hours. It is best not to visit the toilet during this period to avoid story that touches.

Alternately, add one cup of dishwashing liquid, one cup of water softener, and hot water to the toilet. Allow them to sit all night. Flush the toilet in the morning to thoroughly clear the obstruction.


You don’t have to be bed-sick thinking of how to unclog your RV toilet holding tank when there are lots of options you can maximize to continue enjoying your toilet

You can make use of the boiling water method, however, you have to be careful. The use of chemical method is the best and most used method you can try always. Going through this guide again will give you an insight into how to get started.

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