Clogged RV Toilet? [5 Easy Methods To Fix The Problem]

By Ray Roman | December 8, 2021

Do you have a clogged RV toilet? Wondering how to unclog it without going nuts? Picture this: You’ve been on a long weekend getaway in your RV. You’ve had the best time but unfortunately, it is time to return to the real world. 

You’re all packed up and making your final stop at the dumping station.  You open the valve to dump your black water and… nothing happens.  Nothing.  Happens. 

clogged RV toilet

Clogged RV toilet (or the black tank) in an RV?

We’re guessing you don’t have to try too hard to picture this scenario and that more than likely you’re reading this article as you stand at the dumping station frantically searching for assistance from the internet.  Don’t you worry, you’ve come to the right place!

What’s Involved When You Need To Fix a Clogged RV Toilet?

Part of the troubleshooting process will involve adding gallons of water, or buckets of ice, to your black tank.  Consider the capacity of your tank as you start dumping water in it.  You can find the exact size of your tank by looking in your owner’s manual.  If you don’t have one, check google.  

The black tank in most RVs will be smaller than the grey and freshwater tanks.  We’ve listed the average size of tanks per class for you below:

Average black tank sizes

Fifth Wheels – 39-88 gallons

Class A – 31-51 gallons

Class C -27-63 gallons

Class B (Not all have a black tank) 10-26 gallons

This information may become handy as you venture through trial and error to clear any obstruction.  

Remember to only use products that are designed for RVs.  We’ll repeat that a lot in this article because it is important!

Are you ready to unclog your clogged RV toilet? We’ve listed these in what we think is the easiest to more complicated (or lengthy) methods for unclogging an RV toilet.

Just Add Water

Pour a bucket of water down your toilet.  The idea is the rush of water into the tank could move the obstruction and allow your black tank to drain properly. After trying this you still have a clogged RV toilet move on the next method.

Check the Roof Vent

Another quick option is to check the Roof Vent.  A clogged roof vent can create a vacuum that will prevent your black tank from draining.  With the water pump off, have someone flush the toilet inside the RV, if the black tank starts to drain then you know the problem is in the air vent. 

You can clear the vent by removing the cap and sticking in a hose to wash down the blockage.  Keep in mind there will also be a grey tank vent on the roof.

If the smell from the vent doesn’t make it obvious which vent is which, flush them both.  Don’t forget to reseal the caps once you’ve cleared the obstruction. 

If the roof vent is not the problem and you still have a clogged RV toilet there are a few other methods you can use to try and dislodge the obstruction.  

The Drive Around Method

First, you’ll need to purchase a black tank treatment which can be found at most hardware stores or your local superstore.  

Next, get a five-gallon bucket and fill it with hot water and half a cup of dishwashing soap. If you don’t have hot water, cold water is fine.  Hot water is just better at breaking up particles such as toilet paper.  

Dump 2-3 times the normal amount of the tank treatment chemical down the toilet and follow that with the bucket of hot soapy water. If you have the space add an additional bucket or two of hot water (or cold water if you are out of hot).  

Now you take your RV for a drive.  It is not necessary that you drive erratically or unsafely.  You just want the water to slosh around in the tank.  

If you are not pressed for time, letting the tank sit with the chemicals in it for a day or two will give those chemicals time to break down waste and the clog but if you are in a hurry try dumping the black tank after driving around for a while (30-45 minutes).

We’ve also seen people swear by another form of the drive-around method that involves dumping ice in the tank and driving around with it instead of hot water or chemicals. 

Ice is available at most campgrounds so it should be easy to come by.  Dump a bag or two down the toilet and then take your RV for a spin.  After half or a full hour of driving, try emptying your tank again. Hopefully, you no longer have a clogged RV toilet, but if you still do keep reading.  

Try a few hand tools

These are easier things to do but they could be messy so they landed toward the bottom of our list for this reason.

If the clog seems to be higher than the black tank we recommend using a regular plunger (if you can create an air-tight seal) to try to dislodge any particles stuck in the pipe.  

You could also try a flexible toilet tank wand if a plunger isn’t likely to do the trick.  Remember to only use products made specifically for RVs so you do not run the risk of puncturing or damaging the plumbing system. 

The Last Hope

If you believe the clog to be in the black tank itself and you’ve tried all the options above and you’re still unable to drain the tank a final option could be to snake it from the gate valve end.  We know.  Hear us out.  

There is the potential that this will work (which is awesome!) but that means that the tank will then immediately start to drain (which is far less awesome if you are on the other end of that valve).

A way to prevent a large mess would be to purchase an inexpensive sewer hose and drill a hole near the bayonet coupling.  Yes, drilling a hole in the sewer hose will then make it unusable for normal use, that is why we suggest using an inexpensive hose, not a quality hose.  

With proper maintenance and cleaning you should be able to minimize future clogs but on the off chance it happens again, consider keeping the “snake hose” for future use – after it has been cleaned, of course.

Feed the snake through the drilled hole and get to work.  Use something to cover the hole that the snake entered to minimize any mess that will come from the rush of black water if you find success.  

Keep in mind once you’ve cleared the clog you can stop the draining and re-attach your original drain hose which should stop any additional mess from taking place.  

If you still have a clogged RV toilet after trying all the methods above, it is time to call in the professionals.

How Do I prevent RV Toilet clogs in the future?

Most clogged RV toilet situations can be prevented by regular maintenance and care of your black tank.  

Only use toilet paper specifically designed for RVs. Here are our 7 best recommended RV toilet papers.

Don’t dump it too often (leads to a dry tank) or wait too long to dump it (organic material could build up).  We recommend dumping every 3-5 days or when the tank is 2/3 full.  

Never flush sanitary products or flushable wipes.  

Make sure you’re using the correct treatment chemicals and cleaning the tank after each trip. 

Unclog an RV Toilet Summary

Unclogging a toilet is never a fun job.  We hope that our article has at least given you the tools you need to make this crappy chore (see what we did there?) less painful on your wallet than a call to a professional would be. 

If you keep your tank clean and do all the recommended maintenance, clogged toilets shouldn’t be a routine part of your RV lifestyle.  Good luck!

Frequently Asked Questions

  • Can I use a plunger on an RV toilet?
  • Well, yes and no.  If you’re able to create an airtight seal with the plunger you can use it to remove any obstruction that is near the top of the pipe. Unfortunately, tho, anything too far down, or in the tank itself, will not be affected by the plunging action. 

  • What can I pour down a toilet to unclog it?
  • Only pour RV-specific chemicals down your toilet.  The plumbing system in your RV is not like the one in your home.  Do not use anything that isn’t marked as RV safe.

  • How do I unclog a Thetford RV toilet? 
  • The same way you would any other RV toilet.  The ideas listed above should be helpful.  

  • Will a toilet eventually unclog itself?
  • Unlikely.  In fact, it is possible the clog will get worse over time if not dealt with quickly.  You need water flowing through the pipes and in the tank to keep the organic material from hardening and sticking to the internal plumbing.  

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    Ray Roman

    Ray Roman is the co-owner/author of Go Travel Trailers. He is the main contributor of content and an avid researcher of travel trailers and the RV lifestyle. He loves fly fishing, vacationing in Red River, NM, and spending time with family and friends.