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Why Does My RV Toilet Bubble When I Flush?

If your RV toilet bubbles when you flush, there are a few reasons why this happens. This could be due to a blocked drainpipe or blocked black water vent. Your black water tank could also be full or your vacuum breaker could be malfunctioning. This may also be due to debris accumulated at the bottom of your RV holding tanks. 

I’ll teach you how to spot these issues and how to fix them within this article. Keep reading:

Why does my RV toilet bubble when I flush?

At some point, most of the RVers have experienced a bubbling toilet which can actually cause a mess if not addressed as early as possible. I’ll take you through the possible reasons and the solution for each so that can work on it yourself:

1. Blocked drain pipe

When the pipe between the black water drain and the toilet’s drain clogs, you will experience bubbles upon flushing. This is normally caused by bad RV toilet habits, such as flushing cat litter or any solid waste residue.

If this is the reason, be sure to unclog it as early as possible through the following methods:

  • Use the septic declogging chemicals
  • Use an RV black water tank cleaning wand to clear the pipe
  • Use a plumber’s snake to unclog your RV toilet
  • Use ice cubes to unclog the piled-up debris. Pour the ice cubes through your toilet drain and drive around for about 20 minutes. This will loosen the stuck-up debris hence you can easily drain them but don’t forget to rinse it with clean water after draining.

2. Blocked black water tank vent

The vent of your black water may be blocked; so be sure to check if it is clear or not. This vent is the one responsible for channeling out an odor when you flush or empty your black tank.

Sometimes it can be blocked by animals, leaves, or more hence blocking the escaping air hence forcing it to escape through your RV toilet.

Check the vent if there’s any blockage and if there is, get rid of it carefully to avoid damaging the vent.

3. Full black water tank

If you haven’t drained the black water tank, you may experience bubbling in your RV toilet. When there’s no room for more water in the tank, it produces bubbles as an indication since it needs to release out the air after receiving water from the toilet flush.

First, you need to know how your RV toilet behaves when its black water tank is about to fill. Just pay attention to the sound it produces when you flush. Generally, the sound changes hence telling you that it’s getting close to full. However, what if your black water tank is full?

You will need to find a dumping station where you can drain your container. If you fail to do so, it may lead to reverse overflow.

4. Debris at the RV tank bottom

A pile of solids formed at the base of your black tank can also contribute to the occurrence of bubbles. These solids usually pile where the drain enters the tank where it hits the fan. However, it may be a challenge to note this but once you have exhausted all other reasons, you may need to consider this.

If your RV toilet produces bubbles upon flushing due to debris pile up in your black water tank’s bottom, the best way to cure it is by unclogging the blockage. You may be asking yourself how you can about but here are the ways you can employ.

Pour a small amount of hot boiling water, drive around and drain the tank. Boiling water will help you break up the solids or materials causing a blockage in your RV toilet.

Another method is to use an RV cleaning wand to unclog the debris.

5. Malfunctioned vacuum breaker

There could also be a problem with the vacuum breaker. The toilet valve which normally prevents water from being siphoned backward may be broken. So, if this device isn’t functional, it will allow dirty water to flow back which is evident when you observe bubbles.

Always check the condition of the vacuum breaker. In case it is broken, replace it immediately.

How to prevent RV toilet from flushing

Having gone through the possible reasons that cause bubbling in your RV toilet, it is important to note that some RV toilet habits can be fuel the situation. Most of the RVers still have a challenge on what should be avoided when using RV toilets to prevent bubbling. Please note the following:

1. Empty the RV black water tank

Always keep an eye on the tank a couple of times per day so you can address the situation before it strengthens. So, if you are camping, know where you can find a dumping station. Actually, if you are going out, research how far the dump stations are from your destination.

Keep out anything that can fuel blockage or deposition of solids at the base of the black tank: don’t flush anything that is not meant to be flushed down your RV toilet. For instance, diapers, sanitary towels, papers, and other foreign solids.

If you failed to consider this, it will automatically block the system and you will constantly experience bubbles.

2. Employ toilet treatment

There are cleaning solutions such as calcium nitrate that are suitable for your RV black tank. Some solutions will dissolve will some solids and hence can be drained. Apart from that, some may also help eliminate bad odor and most importantly prevent any build-up of unwanted clogging.

Regular cleaning of RV black water tank: ensure that the condition of the RV black tank is stable therefore, you need to pay attention to the ways that we have discussed above when unclogging the tank.

Constantly check on the black water tank vent: sometimes leaves or animal waste pile up there without your knowledge; so keep an eye on the vent. Also, while cleaning it, be cautious not to damage the vent.


1. When do I need to consult a professional?

As we have seen, most of the solutions can easily be solved but some may not. For instance, if the clogging may have been a result of sediment build-up due to iron, magnesium, or calcium, you may require to change the water lines. In other words, it’s more likely a plumbing issue.

Also, some bubbling may be caused by a blockage that needs a professional clearance.

2. What are the main areas to keep an eye on if my RV toilet bubbles when flushed?

Before you check on your RV toilet system, the main areas to consider are your RV black water tank and RV toilet. To differentiate the two, the RV black tank consists of rain pipe, RV black tank bottom, full RV black tank, and the vent of the RV black tank.

And when it comes to the RV toilet, we major on the vacuum breaker.

3. What are signs there’s something wrong with my toilet?

Apart from bubbling, there are some signs that give a warning. So, if you experience a strong odor coming from your toilet or black water tank then you have an issue to address. Also, if you drain your tank but you don’t hear or see anything then there could be a problem.