/ / How To Unclog RV Black Tank? [Step by Step]

How To Unclog RV Black Tank? [Step by Step]

Blackwater tanks are not the most pleasant ones, but they deserve the same tender loving care that any other RV component gets.

A clogged black tank is a nightmare, but someone’s got to do the dirty work. If you’re lucky enough, unclogging your black tank will be as simple as cleaning the junk around the valve. If you’re not, then get ready for some bad news.

Fortunately, you don’t have to get your hands soiled. There are several clean and safe ways to unclog your black tank without having to deal with its contents.

Unclogging the Black Tank: What Not to Do

There are many “solutions” making rounds on the internet that claim to free up clogged black tanks. And chances are, you’ve probably already used some of them to deal with past clogs. But what you might not know is, these may end up worsening the clog. Perhaps, that’s why you’re dealing with this clog today in the first place.

Regardless, here’s what not to do:

  • Don’t use a pressure washer. This is the most common mistake we’ve seen people making. Yes, a pressure washer does clean up your tank. However, it can lead to other problems. Pressure washers may end up puncturing your tank, which is a big no. Plus, you might end up injuring yourself. So, avoid these at all costs.
  • Ditch pressurized air. Pressurized air may seem like the second-best idea, next to pressure washing. But much like pressure washing, it can cause cracks in the tank. Additionally, pressurized air may end up pushing waste into hard-to-reach corners of the tank, worsening the clog.
  • Avoid motorized toilet snakes and toilet snakes for your black tank. Toilet snakes are quite handy, but they’re not the right choice for freeing up a black tank. You shouldn’t use any toilet snake for your black tank. But it’s safe to use toilet snakes to clean up the line that connects the toilet and the tank. Even then, do not use motorized augers, as they tend to puncture the tank and the line.

The Right Way to Clean Your RV’s Black Tank:

Step 1: Prepping Up

Before you begin with any plumbing work, you must prepare yourself, both mentally and physically. Always wear latex gloves when handling blackwater; this one’s a no-brainer.

But since you might be using chemicals as well, try buying protective eyewear. Also, check the manufacturer’s recommendation for the type of safety equipment needed to handle the chemical you’re using.

Psychologically, be prepared for the worst. Unclogging a backwater tank may be as pleasant as simply cleaning the valve or as nasty as manually dumping the contents. If you’re not comfortable working with blackwater, consider calling someone else.

Step 2: Cleaning the Line

Now on to the cleaning methods. Since no one wants to deal with blackwater, it’s generally a better idea to first try other methods. Instead of cleaning the tank, you can try cleaning out the line that connects the tank to your toilet. This line can develop pyramid plugs, which may be the cause of your issue.

The easiest way to deal with pyramid plugs is with an auger, a kind of toilet snake. This will go deep into the toilet’s line and help pull out any visible clogs.

Be sure only to use this for the line and nowhere else. Also, avoid motorized augers. These augers may end up puncturing the blackwater tank, which will wreak havoc on everything.

You can try another method, which involves dumping a soap solution down the toilet. Fill your blackwater tank halfway with water, then add a bit of liquid soap. Run your RV around for a bit and let the soap solution do its magic.

If you’re lucky enough, it will soften up any challenging clogs, and you can safely flush the line.

Step 3: Checking the Valves

In case cleaning the lines doesn’t work, you can try checking the valves. The first valve you should check is the gate valve. The gate valve should be letting out some amount of liquid unless it’s completely clogged up.

To check this, look for the blackwater T-handle. It’s usually placed close to the greywater T-handle. Try pulling it. If the T-handle can be pulled back and forth with little to no resistance, then your gate valve is faulty.

You can fix this by manually opening the gate valve. A lot of blackwater will come out when you do so, so be prepared. If your tank starts draining like normal, then your issue is fixed.

If not, it means you need to do some more cleaning. Sometimes, there’s a clog right behind the valve that’s preventing anything from coming out. You can fix this by backflushing the toilet, hopefully breaking up any clogs and freeing up the valve.

You can use several products that will shoot water up the valve, breaking up any clogged waste. If the waste is toilet paper or plastic, it will work better. If it’s something else, you’ll need to do more work.

Step 4: Using Chemicals

If all else fails, you’ll have to deal with the blackwater tank, waste, and all. Luckily, you can avoid having to mess with the tank personally. Instead, you can use some chemicals that will make the job less disgusting.

These chemicals come in many forms. Some will come as drops that will clear up any clogs in your blackwater tank with a single drop. Others will require more handiwork. But the result will hopefully be satisfactory.

Step 5: The Ice Cube Method

This may sound like an unconventional idea, but it’s either this or dealing with your black tank. The trick here is to fill your blackwater tank halfway with water. Then top the rest of it off with ice cubes. And yes, as you may have guessed, you’ll need a lot of ice cubes.

But the idea here is that the ice cubes will break up anything that’s clogging the black tank. If you find this method useless, you can skip over to the next method.

Step 6: Boiling Water Method

If all else fails, there’s one last method you can try. In this, you take boiling water and pour it down the toilet. You’ll need a lot of water, enough to fill half or three-fourths of your black tank.

Let the water sit overnight, and then drain the tank in the morning. The heat from the boiling water will hopefully unclog anything that’s blocking the blackwater tank.

This should fix up most clogs. And if not, then your only hope is to call a professional. They may be able to look at your blackwater tank and determine both the cause of the clog and its solution.

Preventing Future Clogs

So, you’ve finally unclogged your black tank. Now, wasn’t that unsettling? To save you from doing the dirty work in the future, here’s how you can prevent clogs:

  • Watch what you flush. This is a simple preventive measure. While human waste can lead to clogs, most clogs are caused by flushing the wrong items down the toilet. Avoid flushing toilet paper, plastic bags, and small items.
  • Clean your black tank regularly. Dealing with smaller clogs will prevent bigger clogs that will be harder to cure. Apply any of the above cleaning methods at least once a week.
  • Keep the sensors in check. You can’t take a peek into your tank, so the sensors are your eyes and ears. Keep them in check, as clogged or malfunctioning sensors will inhibit accurate readings.
  • Dump the black tank often, but not too much. Don’t wait a lot to dump the tank. As soon as you’re on a road trip, dump your tank in a dumping ground. But don’t dump it all the way. This will cause any solid waste to sink to the bottom, causing a clog.
  • Use special RV black tank chemicals only. Not all household drain cleaners will work with your RV’s black tank. Make sure the chemical is rated just for your RV.


Cleaning out a black tank is a nasty job, but someone’s got to do it. Luckily, you can use a few methods to unclog your tank without dealing with its contents.

But more importantly, knowing the right way to clean the tank is knowing the wrong way. After all, you don’t want to damage your tank and worsen the clog.

You can be a bit more mindful of what you flush down the toilet and prevent an unnecessary clog in the future. It’s better than dealing with some nasty business.

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