Help! RV Toilet Filling With Water After Flushing: Causes and Solutions

Help! RV Toilet Filling With Water After Flushing: Causes and Solutions

Posted by Happy Campers Store on Apr 3rd 2024

RV Toilet Filling With Water After Flushing: Causes and Solutions

If you own an RV, you may have encountered the issue of your RV toilet filling with water after flushing. Unlike regular house toilets, RV toilets operate differently and do not have standard tanks or flappers. Their simple design can lead to specific problems that cause the toilet to fill with water. In this blog post, we're going to cover two commonly asked questions that overlap, but are distinctly different in nature.

Question 1;

What causes an RV toilet to fill after flushing? We will also provide you with practical solutions to fix these issues. 

Question 2;

Why is my RV toilet backing up? We will also provide you with practical solutions to fix these issues. 

I. Understanding the Problem:

Before we delve into the causes and solutions, let's first understand why your RV toilet may be filling with water after flushing. RV toilets use a gravity-flush system, which relies on water pressure to remove waste. The water level in the toilet bowl should return to its normal level after flushing. If it continues to fill with water, there may be an underlying issue that needs to be addressed.

An RV toilet filling with "water" should not be confused with an RV toilet backing up. 

II. Causes for RV Toilet Filling After Flushing:

1. Partially Clogged Waste Line:

A partially clogged waste line can cause water to back up into the toilet bowl after flushing. This can occur due to the accumulation of waste, toilet paper, or other debris in the plumbing system.

2. Faulty Flush Mechanism Seal:

The ball valve, located at the bottom of the toilet bowl, controls the flow of water into the waste line. If the ball valve is not closing properly or is damaged, it can allow water to continuously flow into the toilet bowl after flushing.

3. Malfunctioning Water Control Mechanism:

The water control mechanism, which regulates the water flow during flushing, may be malfunctioning. If it fails to shut off completely, water will continue to fill the toilet bowl.

4. Improper Ventilation:

Inadequate ventilation in the RV's plumbing system can create a vacuum effect, causing water to be drawn back into the toilet bowl after flushing. This can happen if the vent pipe is blocked or obstructed.

III. How to Fix an RV Toilet that is Filling with Water:

Now that we understand the possible causes, let's explore the solutions to fix the problem of your RV toilet filling with water after flushing.

1. Clear the Waste Line:

To address a partially clogged waste line, use a specialized RV toilet auger or a plumbing snake to clear any obstructions. Follow the manufacturer's instructions and be cautious not to damage the plumbing system.

We have written an in-depth post on how to unclog an RV Toilet waste line here;

2. Inspect and Replace the Flush Mechanism Seal:

Inspect the ball valve for any signs of damage or wear. If necessary, replace the ball valve with a new one. Ensure that the new valve is properly aligned and functions correctly to prevent water from continuously filling the toilet bowl.

All About RVs has a great video on how to replace a faulty seal on the flush mechanism. This is the most common source of water filling an RV toilet and it's fairly easy to replace. It's worth noting that there are several different brands and types of RV toilets, so they are not all going to be the same or as easy to replace a seal in as this video shows.

These steps provided in this video use the following parts:

Dometic 310 Toilet

Dometic 310 Toilet Seal.

Valve Grease

3. Check and Adjust the Water Control Mechanism:

Inspect the water control mechanism, which is usually located near the back of the toilet bowl. Ensure that it is functioning properly and shutting off completely after flushing. Adjust or replace the mechanism if necessary.

4. Verify Proper Ventilation:

Check the vent pipe connected to the RV's plumbing system for any blockages or obstructions. Clear any debris or buildup that may be hindering proper ventilation. If the vent pipe is damaged or obstructed, consider seeking professional help to repair or replace it.

How Much Water Should Be In an RV Toilet Bowl?

The amount of water in an RV toilet bowl can vary depending on the specific model and design of the toilet. However, as a general guideline, the water level in an RV toilet bowl should be sufficient to cover the bottom of the bowl and create a seal to prevent odors from escaping the holding tank.

Typically, the water level in an RV toilet bowl should be around 1-2 inches deep. This provides enough water for effective waste removal and helps prevent clogs. It's important to note that the water level may fluctuate slightly depending on the specific toilet model and the water pressure in your RV's plumbing system.

If you notice that the water level in your RV toilet bowl is consistently too low or too high, it may indicate an issue with the toilet's water supply or flushing mechanism. In such cases, it's recommended to consult the manufacturer's instructions or seek professional assistance to ensure proper functioning of the toilet.

Remember, maintaining the appropriate water level in the RV toilet bowl is essential for proper waste removal and preventing odors. Regularly check the water level and adjust if necessary to ensure a functional and hygienic toilet system in your RV.

Why Does My RV Toilet Keep Backing Up?

OK. So this part of the post really focuses on the second question of dealing with a backed-up RV toilet. This isn't just water filling up the toilet bowl - it's waste. Understanding the causes behind an RV toilet backing up is crucial in order to prevent future clogs and maintain a properly functioning toilet system. In this article, we will explore the common causes of RV toilet backing up and provide practical solutions to address these issues. Let's dive in!

1. Insufficient Water Usage:

One of the primary causes of an RV toilet backing up is not using enough water when flushing. RV toilets rely on water to effectively flush waste down the system. When insufficient water is used, waste can accumulate and cause clogs.

Solution: Ensure that you use an adequate amount of water when flushing the toilet. This helps to create enough force to push waste through the pipes and prevent clogs. Consider holding down the flush lever for a few extra seconds to allow more water to flow through the system.

2. Excessive Toilet Paper Usage:

Using too much toilet paper can also lead to RV toilet backups. RV plumbing systems are more sensitive compared to residential systems, and excessive toilet paper can easily cause clogs.

Solution: Use toilet paper sparingly and consider using RV-specific or biodegradable toilet paper. These types of toilet paper are designed to dissolve quickly and reduce the risk of clogs. Additionally, you can try using less toilet paper per flush or consider using alternative methods of waste disposal, such as using disposable liners or wipes.

3. Incorrect Toilet Paper Type:

Using the wrong type of toilet paper can contribute to RV toilet backups. Some toilet papers are not designed to break down easily, leading to clogs and blockages in the plumbing system.

Solution: Opt for RV-specific or biodegradable toilet paper, as they are specifically formulated to dissolve quickly and minimize the risk of clogs. These types of toilet paper are readily available at most RV supply stores and online retailers.

4. Other Contributing Factors:

While insufficient water usage, excessive toilet paper usage, and using the wrong type of toilet paper are the primary causes of RV toilet backups, there are a few other factors that can contribute to this issue:

1. Tank Overfilling: 

If the holding tank is full or near capacity, it can cause the toilet to back up. Regularly emptying the holding tank is essential to prevent backups.

2. Foreign Objects: 

Accidentally flushing foreign objects down the toilet, such as feminine hygiene products, wipes, or other non-biodegradable items, can lead to clogs and backups.


Empty the holding tank regularly to prevent overfilling. Be mindful of what you flush down the toilet and avoid disposing of non-biodegradable items or foreign objects.

Ultimately, what you're dealing with is some type of clog in your RV's septic system. If you have a clogged RV toilet or holding tank, you're going to want to check out our complete guide on diagnosing and fixing a clogged RV toilet;

IV. Tips for Preventing Future Issues:

To avoid encountering the problem of your RV toilet filling with water after flushing, consider the following preventive measures:

1. Use RV-Friendly Toilet Paper:

Use toilet paper specifically designed for RVs, as it dissolves quickly and reduces the risk of clogging the waste line.

2. Practice Proper Waste Disposal:

Avoid flushing large amounts of toilet paper or other non-biodegradable items down the toilet. Dispose of solid waste in designated receptacles to prevent clogs and backups.

3. Conduct Regular Inspections:

Regularly inspect your RV toilet and plumbing system for any signs of leaks, damage, or blockages. Addressing minor issues promptly can prevent them from escalating into major problems.

4. Educate Yourself:

Familiarize yourself with your RV's toilet system and its components. Understanding how they work will help you identify and address any issues that may arise.


Dealing with an RV toilet that fills with water after flushing can be frustrating, but by understanding the possible causes and implementing the solutions mentioned in this blog post, you can effectively fix the issue and prevent it from recurring. Remember to clear any waste line obstructions, inspect and replace the ball valve if necessary, check the water control mechanism, and ensure proper ventilation in the plumbing system. Regular maintenance and preventive measures will help ensure a trouble-free RV toilet experience during your travels.