Black Tank Vents: How to Assess and Fix a Clogged RV Sewer Vent

Christopher London
5 min readFeb 20, 2024

That Sewer Smell Could be a Clogged Roof Vent from Your RV’s Black Tank

RVing is a fantastic way to explore the great outdoors, but it also comes with its fair share of maintenance tasks. One such task is dealing with a clogged RV sewer vent or RV black tank vent. This issue can lead to unpleasant odors and even potential health hazards. This blog post will guide you through the process of assessing and fixing a clogged roof vent in your RV.

Firstly, it’s important to understand what an RV sewer vent is and why it’s crucial. The vent allows gases to escape from your RV’s black tank, preventing buildup and ensuring the system operates correctly. It works similarly to a P-trap under your kitchen sink. When this vent gets clogged, it can cause a range of issues, including slow drainage, gurgling noises, and unpleasant odors.

So, how do you assess if your RV sewer vent or RV black tank vent is clogged?

The first sign is usually a foul smell coming from your RV’s plumbing system. If you notice this, it’s time to investigate further.

Most people start with the toilet and quickly move to the black tank for the issue. While this is the place to start, if you’re sure you’ve cleaned and cleared your holding tank then there is most likely a clogged sewer vent.

Understanding Your RV Sewer Vent Stack

The vent stack on your RV’s black tank is essentially a straight pipe made of 1 1/2" PVC that connects to an opening on the top of the black tank and extends through the RV’s roof. As you may know, there’s a removable cap on top.

There could be several issues causing a clog:

Firstly, your tank might be “dry” due to a leaking valve.

To resolve this, fill the tank (if you don’t have a black tank flush valve, use the toilet’s foot pedal and flush repeatedly until the tank is full and gurgles. Then, empty the tank and repeat the process. Aim to dump a full tank 3 or 4 times after filling it with fresh water.

Secondly, the vent stack might have detached from the tank, meaning the 1 1/2" PVC has pulled out of the black tank’s top.

To check this, gently twist the pipe extending through the roof. If it moves, you might have a leaking vent stack issue, although this is less likely.

Thirdly, your black tank might be dirty.

While all black tanks are inherently dirty, yours might have residue stuck to the side walls from years of use without adequate flushing. The best way to remove this is with mechanical action (sloshing water) on the tank’s sides.

We dive deep into how to thoroughly clean a black tank in another post; Learn how to prevent and address RV black tank clogs.

Here is an overview of the steps to use The Extreme Cleaner to Totally Clean your black tank.

1. Make sure your black tank valve is closed.

2. Turn off the fresh water.

3. Mix 1 entire container of Extreme Cleaner into a bucket or toilet bowl full of water. Flush the product and water down.

4. If you are mobile:

Drive your camper/trailer around for a good 45 minutes to make sure what’s in the holding tank gets swashed around real good.

Dump your black tank and rinse.

4b. If you are stationary (can’t drive around):

Add as much hot water into your holding tank along with the full container of Extreme Cleaner.

Let this sit in your tank for 24–72 hours. Better results for 48–72 hours, but we can’t always wait that long, can we?

Empty your black tank.

5. Use your built-in rinser, a tank wand or backflusher to make sure your tank is clear.

6. Turn your fresh water valve back on.

Lastly, it could simply be that the wind is pushing air down the vent stack, and when you flush, the airflow brings a “gentle breeze” up through the toilet.

What can you do to solve that little problem?

Get the Camco Cyclone Sewer Vent:

This vent allows you to use the power of the wind to draw holding tank odors out of your RV. Even a gentle breeze works with the dynamically engineered shape of the Cyclone to create a powerful vortex that pulls odors up and away. Attaches easily to any RV plumbing vent.

How to Check for Sewer Vent Blockage:

Start by visually inspecting the vent on your RV’s roof.

If you see any obvious blockages, such as leaves, bird or bee nests, this could be the cause of your problem. However, sometimes the blockage isn’t visible from the outside. In this case, you’ll need to do a more thorough inspection.

To do this, you’ll need a garden hose with a spray nozzle. Insert the hose into the RV sewer vent and turn on the water. If the water backs up and doesn’t drain, this is a clear sign that your RV black tank vent is clogged.

Once you’ve confirmed that your RV sewer vent is clogged, it’s time to fix the problem. If the blockage is visible and easy to reach, you may be able to remove it manually. Be sure to wear gloves and use a tool like a long stick or a plumber’s snake to dislodge the blockage.

If the blockage is further down the vent, you’ll need to use a method called “water jetting.”

This involves using a high-pressure water jet to break up the blockage. You can either hire a professional to do this or purchase a water jetting kit and do it yourself.

After you’ve removed the blockage, it’s a good idea to clean your RV sewer vent to prevent future clogs. You can do this by running a large volume of water down the vent to flush out any remaining debris.

In conclusion, dealing with a clogged RV sewer vent or RV black tank vent can be a bit of a hassle, but it’s a necessary part of RV maintenance. By regularly inspecting your vent and taking action at the first sign of a problem, you can keep your RV’s plumbing system running smoothly and enjoy your adventures on the open road.

No More Clogged Roof Vent in Your RV

Remember, a well-maintained RV is the key to a successful and enjoyable RVing experience. Don’t let a clogged RV sewer vent or RV black tank vent put a damper on your adventures. With the right knowledge and tools, you can assess and fix the problem with ease. Happy RVing!

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Christopher London

Chris London, Owner/Marketing Director for Pixel Productions Inc, is an expert in brand building, Ecommerce Development, and online marketing.