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Why Does My RV Toilet Bubble When Flushed?

Everyone fears that random issue with your plumbing that can mess up your Saturday plans, but with your recreational vehicle? That’s next-level dreadful.

Problems with your toilet are terrible wherever they happen, but on the road, with your partner, while driving your RV across interstate lines, they become an even worse nightmare. A plumbing malfunction on the road is a surefire way to instigate panic, dampen the mood, and diminish the enjoyability of your trip.

Why all this trouble with your RV toilet? Why is your RV toilet bubbling when you flush?

Like with any regular toilet, your RV toilet bubbles or burp because of some kind of blockage.

The issue could stem from your black tank being full or congested from buildup, a blockage in the air vent connected to the black tank, or a back-uped drain pipe impeding the flow of matter between the toilet bowl and the black tank.

Once there is any form of partial or total blockage along the RV toilet’s network, the chances are that you will end up with bubbles when you flush.

Yes, we have given you a broad overview of what could be wrong, but that is obviously only half the answer.

You are probably wondering how you find out which one of these potential problems could be the issue, how you fix the issue and fix it fast, and how to prevent it from happening in the future. No worries, we have got you covered.

To help you navigate this mess, our editors have created this knowledge base article that contains everything you need.

Potential Problems Making Your RV Toilet Bubble When Flushed

RV toilets bubbling is one of the most reported lavatory problems with campers and mobile caravans. This fact is unsurprising because problems are bound to occur when you build a toilet system while being that strapped for space.

The toilet bubbling when you flush is one of the most prevalent problems, and here are all the potential reasons why it could be happening.

Worn Out Rubber Components

Recreational vehicles can last quite a long time. There are tales across the internet of Scamp trailers bought during their initial launch in 1972 that are still on the road today.

With this extreme lifespan comes potential faults from wear and tear, and like you would find in most living spaces, the plumbing is first to go in an RV too. One primary reason your RV toilet bubbles when flushed may be because of worn-out components along the sewage line.

Common culprits include the toilet valve, which helps to keep dirty water from flowing backward, the fill valve, which blocks airflow from the tank back into the toilet, and the waste valve, which regulates the flow of water from storage into the toilet bowl.

If your RV is old enough, the chances are that one of these components may be aged and worn.

If these valves slack enough, they could allow excessive air—and consequently air bubbles—to enter the system, causing your RV toilet to bubble every time you flush.

Editor’s Note

Aside from these general wear and tear in your toilet system, most of the other potential problems that cause toilet bubbles will be connected to the black tank (the waste storage tank for your RV’s toilet system)

Filled Black Tank

The most straightforward of these problems? Your black tank is full.

While you are busy racking your brain as to why your RV toilet burps, the problem may be as common and simple as having a full black tank.

Once your black tank reaches its total capacity, it is forced to send (nasty-smelling) air bubbles back into your toilet. Plus, if you leave this problem unattended, you may end up with black tank waste seeping back into your toilet bowl. And you wouldn’t want that.

Most RV toilet units today come with a user-friendly tank monitor that alerts you when the accretion of waste has reached a critical level and requires emptying.

However, in some cases, this monitoring system may be acting up or be inaccurate, giving you an erroneous “not full” reading and consequent supply of toilet bubbles when you flush.

Black Tank Congested with Buildup of Solid Waste

What if you just emptied your black tank at your last stop, yet your RV toilet still bubbles when you flush? Then your RV toilet’s black tank may not be emptying well enough.

As you use your RV toilet system, a significant amount of stuck solid waste may begin to build up from the base of your black tank.

Anything flushed down your toilet bowl that doesn’t dissolve easily or flow while emptying the tank will continue to add to this backlog of sludge that continues to amass in the black tank. Common culprits include thicker toilet paper, wet wipes, and other items you should never flush down a toilet, like tampons and condoms.

With prolonged toilet use, this unshifting mass at the base of your black tank may build up enough to the point where it causes toilet bubbles when you flush.

Clogged Black Tank Air Vent

Sometimes, the bubbling problem you are getting when flushing your RV toilet may stem from a blockage of air rather than one of solids and liquids.

Like most complete sewage systems, your RV toilet unit comes complete with waste storage (black tank) and an air vent connected to the tank that acts as an outlet for the release of Nitrous gasses that can build up over time.

Typically, the air vent is a long pipe that extends from the black tank at the bottom of the vehicle to the roof (or near) of your camper, where it houses the release outlet.

If this conduit gets clogged or blocked (by leaves, dust, or dirt,) a significant mass of nitrous gasses begins to build up in the black tank. Once the black that reaches its max gas holding capacity, every flush of your toilet will force air from the black tank back into the toilet blow, causing bubbles (and probably a bad smell too)

Blocked Drainage Pipe

Another component connected to the black tank that can end up blocked is the drainage pipe.

The drainage pipe is the protruding pipe underneath your RV that extends from the black tank and acts as the connection point for your sewage hose while you are emptying the tank.

In rare cases, this pipe may get blocked by the buildup of solid matter over time. Once clogged, the drainage pipe will significantly reduce the effectiveness of each tank emptying session, leading to the buildup of solids, liquids, and gasses in the black tank and potentially causing bubbles when you flush.

Troubleshooting Your RV Toilet to Stop Bubbling When You Flush

By now, you are already well acquainted with most of the possible reasons why your Camper toilet bubbles when you flush. However, how do you figure out the exact cause of your RV toilet’s burping, and how do you fix it?

Here are some primary troubleshooting steps to figure out the problem and fix it fast.

Replace Worn Out and Broken Components

The fix for your RV toilet burping may be as simple as replacing a rubber valve or other component that is broken or worn out.

Procedure: check your entire RV toilet unit and sewage lines for any signs of wear and breakage and buy replacements for the affected parts.

Empty Your Black Tank Again

If you notice your RV toilet bubbling, the first troubleshooting step you should take is to empty your black tank, even if you unloaded it a short while ago.

While the chances are that the problem may be a bit more complex, emptying your tank is an easy step that eliminates the most basic possible problem, so you are sure it is something else before you begin to try more elaborate fixes.

Procedure: Stop at the dump station closest to you, connect your sewage hose to the terminal, and then allow enough time to empty your black tank entirely. Once the process completes, you should run fresh water through your black tank a few times, filling it up and emptying it again.

Suppose your toilet bubbling problem stems from a temporary blockage anywhere along your toilet system. In that case, this flushing of the entire system should be enough to dislodge the blockage and fix the issue.

Recheck your RV toilet by flushing it to see if it burps. If this procedure fixes it, then it’s back to happy times. If the issue persists, you should proceed to try these other troubleshooting tips.

Check Your Black Tank Air Vent for Blockage

If emptying your black tank doesn’t work, the next section of your toilet system you should check is the black tank air vent.

No thanks to its location at the top of the RV, the black tank air vent is one of those corners of our campers that rarely get any attention. Even some of the most seasoned RV enthusiasts will never have looked at their black tank air vent even once.

Since the air vent has holes to let gasses escape the black tank, it could also provide an inlet for debris, leaves, bugs, mud, or even birds and rodents to enter and potentially clog the vent.

Procedure: Armed with a flashlight, climb to the top of your RV using a ladder and locate the top of your black tank air vent. Scan the inside of the duct for any impediments that may obstruct the airflow. If you find any, you can clean the vent using any pressurized water sprayer or a snaking hose connected to any water supply.

Treat Your Black Tank for Solid Waste Buildup

If you have made sure your vent is clog-free and have emptied your black tank multiple times without fixing your RV toilet burping problem, then it is time to move on to more advanced measures.

If both prior methods fail, there is a high chance that the issue stems from persistent solid waste buildup in the tank or the drain pipe that couldn’t be dislodged by simply flushing the system with water. Your best bet here is to treat and clean the tank again using chemical treatments.

Procedure: While there are several common home remedies for dealing with the issue—such as driving around with a load of ice cubes or a mixture of detergent, bleach, and hot water stuffed into the black tank—we recommend you opt for a reliable industrial-grade black tank cleaner instead. Heavy-duty chemical cleaners will easily dissolve any persistent solid waste buildup in one wash. Make sure to follow the instructions on the cleaner’s packaging to a T.

Snake Your Drainage Pipe

The next part of your toilet system you should attack to clear any residual waste buildup is the drainage pipe.

Procedure: Pressurized water is the best way to clean your drainage pipe thoroughly. Use any pressurized water sprayer or a snaking hose connected to a water supply to force water through the pipes and dislodge any backed-up solid matter.

Consulting a Professional

If all of these troubleshooting methods fail, the chances are that you won’t be fixing this problem without some external help.

In such extreme cases, the bubbling of your RV toilet may result from structural issues with your toilet or the breakage of specific invisible valves that will likely be found only by a professional who deals with RV toilets and sewer systems.

Procedure: Contact the nearest RV professional and schedule a checkup of your RV toilet system.

Preventive Measures to Mitigate RV Toilet Bubbles During Flushing

RV toilets are an essential part of the mobile living experience; hence, we must have them perform optimally, all the time. Once you manage to stop your RV toilet from bubbling when you flush, you should take steps to ensure it never happens again.

The best way to handle toilet burping issues is to implement specific usage practices that prevent this problem from popping up in the first place.

Some of the best preventive measures to employ include:

  • Always flush your RV toilet with excessive amounts of water to prevent any buildup
  • Treat your black tank with a chemical cleaner at least once a month
  • Have a plumbing snake or a sewer hose attachment handy at all times
  • Inspect your air vent for blockages periodically
  • Consider replacing your regular toilet paper with RV-safe toilet paper
  • Avoid flushing any foreign objects like tampons or condoms down your RV toilet

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