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Is your RV’s black tank clogged and refusing to drain?
Learn what causes this, the best way to unclog it, and preventive measures to keep your RV’s plumbing system running smoothly.
Important: Below are the most effective ways to unclog a black tank that won’t drain, not to unclog a camper toilet. They are two similar but separate issues. If your camper’s toilet is clogged and won’t empty into the black tank, then check out our guide on how to unclog an RV toilet.
Why is My RV Black Tank Not Draining?
If you hooked up your sewer hose, opened the holding tank’s gate valve… and nothing happens, you likely have a blockage or clog in one of two spots.
1) Outlet Inside Tank is Blocked
One of the most common reasons your RV black tank won’t drain is because the outlet inside the tank is blocked. This obstruction prevents the waste from exiting the tank, leading to a clog.
2) Clog in Outlet Sewer Line
Another common issue is a clog in the outlet sewer line. This can happen when solid waste, toilet paper, or other non-dissolvable items get stuck in the pipe, creating a physical barrier.
Causes of RV Black Tank Clogs
Leaving the Black Tanks Open When Connected to Sewer
Leaving the black tanks open when connected to a sewer is usually a newbie mistake that can lead to clogs and the infamous poop pyramid. This is because the liquid waste drains away, leaving the solid waste behind. Over time, this solid waste can build up and harden, leading to a blockage of the outlet or even a clog in the inlet pipe.
Tip: If your camper toilet won’t empty into the black tank and you’ve been leaving the black tank valve open when connected to the sewer, you likely have a poo pyramid! Check out how to get rid of the poo pyramid for important step-by-step instructions.
Storing Without Dumping
Storing your RV without first dumping the black tank can lead to significant clogs and other issues. As liquids evaporate, the solid waste can harden over time, making it difficult to remove when you finally try to empty the tank.
Not Using Enough Water with Each Flush
The water helps to break down the waste and move it through the system. Without enough water, the waste can build up and harden, leading to a clog.
A Leaking Black Tank
If the tank is leaking, it may not be holding enough water to properly flush the system. This can lead to a buildup of solid waste and a subsequent clog.
Not Filling Your Black Tank After Dumping
It’s important to always Fill your RV’s black tank about 10% with water after each dump. The water helps to break down any remaining waste and flush it out of the system. Without this water, the remaining waste can harden and cause a clog.
Using “Flushable” Wipes
Despite their name, these wipes do not break down as easily or as quickly as regular toilet paper. When these wipes are flushed into the black tank, they can accumulate and form a thick, hard mass that can block the tank’s drain.
Struvite Formation
Struvite, a mineral compound composed of magnesium, ammonium, and phosphate, can form in your black tank and sewer plumbing. Depending on the level of buildup, you may need to use a special struvite remover if “blasting” it out using the method below doesn’t work.
How to Unclog an RV Black Tank
The two most effective techniques to remove a clog and get the tank draining again are to reverse flush the black tank or use a powerful black tank treatment. Let’s learn how to perform each technique step-by-step.
Flush the Black Tank
One of the most effective ways to unclog an RV black tank is to flush it. This involves pumping water into the tank in the opposite direction of the normal flow to dislodge the clog.
This is easy to do with a product like the Camco Rhino Blaster Pro.
Camco Rhino Blaster Pro RV Tank Rinser
Price:Clicking this link to make a purchase may earn us a commission at no additional cost to you.
The Rhino Blaster is a powerful tool that injects a high-pressure stream of water into the sewage pipe, effectively removing any clogs and cleaning the tank. Its 45-degree angle design ensures the water flows seamlessly through the pipes and into the tank.
How to Use the Rhino Blaster Pro to Remove a Clog
- Ensure the holding tank gate valve is closed, and remove the cap from your RV’s sewer outlet.
- Connect the transparent end of the Rhino Blaster to the sewer outlet using the swivel bayonet fitting.
- Attach your sewer hose to the other end of the Rhino Blaster.
- Connect the black vacuum breaker between the faucet and the water hose, then connect the other end of the water hose to the threads on the side of the Blaster.
- Ensure all connections are securely fastened.
- Open the gate valve to the black tank.
- Switch the water hose knob to the “on” position to initiate the flushing process.
- Close the gate valve on the Rhino Blaster Pro. You’ll notice water filling up in the Rhino Blaster Pro as it moves through the pipe and into the black tank, removing the clog.
- Turn off the water, open the valve on the Rhino Blaster, and let the contents drain out.
- After the contents of the black tank have drained out, it’s a good idea to flush the tank again while you have the Rhino Blaster Pro still connected.
Important: Use the supplied vacuum breaker with the Blaster to avoid contaminated water flowing back into the hose. Use a water hose marked “not for drinking water use.”
Camco Rhino Blaster Pro RV Tank Rinser
Price:Clicking this link to make a purchase may earn us a commission at no additional cost to you.
Use a Black Tank Treatment
A black tank treatment can also help unclog your RV black tank. These treatments contain enzymes and bacteria that break down waste, removing any clogs in the system.
Arguably, the best product for this job is Unique’s Clear-It!
Unique Clear-It
Price:Clicking this link to make a purchase may earn us a commission at no additional cost to you.
This product effectively eliminates clogs in black water tanks and plumbing systems with its blend of enzymes and bacteria that quickly break down and digest toilet tissue, waste, and sludge.
Simply add it to your tank and let it work its magic over 48-72 hours. There’s no need for any driving!
Check out their quick product video!
Preventing RV Black Tank Clogs
Proper Flushing Techniques
Using proper flushing techniques can help prevent clogs. This includes using enough water with each flush to help break down waste and move it through the system.
Regular Dumping and Cleaning
This includes emptying the tank and thoroughly cleaning it to remove any residual waste that could harden and cause a clog.
Tip: Check out our guide on how to clean an RV black tank for our exact step-by-step process.
Proper Disposal of Wipes and Non-Toilet Paper Items
Despite being marketed as “flushable,” many of these items do not break down as easily as toilet paper and can lead to a buildup of waste in the tank.
It’s best to avoid using “flushable” wipes in your RV altogether. If you must use them, dispose of them in a trash can rather than flushing them down the toilet.
Importance of Closing the Black Tank’s Gate Valve
Leaving the black tank’s gate valve closed until it comes time to dump is crucial in preventing clogs. Leaving the valve open can allow liquid waste to drain, leaving solid waste behind that can harden and cause a clog. Remember the poop pyramid mentioned above? This is the number reason for that to form. Don’t do it!
Cleaning Tanks Before Extended Storage
Dumping and cleaning your black tank before putting your RV in storage for an extended period can help prevent clogs. If waste is left in the tank during storage, it can harden and cause a clog when you try to empty it later.
Regular Use of Holding Tank Treatments
These treatments contain enzymes and bacteria that break down waste, making it easier to flush out of the system.
Here are a few of the best holding tank treatments as well as some homemade holding tank treatment options you can try.
Black Tank Inspections
By regularly inspecting your tank, you can identify and address potential issues before they lead to a clog, mainly leaks.
Related: Why Does My RV Black Tank Leak When It’s Full?
By understanding the causes of RV black tank clogs and taking steps to prevent them, you can keep your RV’s plumbing system functioning smoothly. Remember, prevention is always better than cure, especially when maintaining your RV’s black tank.
Great article!! I learned of a procedure that I was not aware of. And, I am sure most campers are doing it wrong too……thanks!!
Thanks Adrian!