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What To Do When Your RV Black Water Tank Is Clogged

Having a mobile bathroom in your RV is quite helpful on the road and keeps you from having to use public facilities that often aren’t as clean as you’d like. With having your own bathroom also comes the possibility of extra maintenance though. Having your RV’s black water tank clog is one of the grossest issues you can deal with in an RV.

Thankfully, it’s not that difficult to unclog your black water tank, in the event it does get clogged. There are also more than a few ways to tell if your black water tank is clogged.

The first step is knowing that your black water tank is clogged. We’ll discuss a few observations you can make. Finally, using ice or other methods might help.

How do you know your RV black water tank is clogged?

Before you begin methods to unclog your RV black water tank, make sure it’s actually clogged first. Here’s how to know that your black water tank is clogged

It doesn’t drain

Try to drain your black water tank, using a clear hose adapter if possible. If you don’t see solid waste coming out and you know there is solid waste inside, you probably have a “poop pyramid” or something like it.

You can smell it

Having a clog somewhere in the line for your black water tank can prevent solid and liquid waste from moving into the black tank – leaving it in the black water line for your nose to inhale.

It’s coming out of your toilet

This could mean you are overflowing and clogged. Having solid and liquid waste backed all the way up to your toilet is a bad sign indeed. First, try draining it, then if draining it doesn’t help – try the upcoming unclogging methods.

How do unclog your black water tank

There are a few tried and true methods. We’ll start with the easiest first.


Ice is one of the easiest methods. Either buy a bag at a gas station or grocery store, or freeze ice cubes in your freezer. Empty the tray or bag (or at least part of it) into your toilet. 

Drive the RV around for a little bit to allow the ice to flow throughout your tank.

This method can break up clogs by having solid pieces of ice ram into the clog to attempt to remove it.

When done, attempt to drain the tank again and see if solids and liquid comes out.

Boiling water

A clog can be removed with ice, or melted. Melting a clog sounds gross, but it works. 

Get a big pot of water and boil it on the stove. Ensure that no one is in your way on the path to the bathroom.

Slowly dump the pot of boiling water into the toilet and flush if necessary. The hot water can melt clogs in the line and potentially break up any clogs inside the black water tank itself.

Like with ice, try to drain your tank and see if anything solid or black/brown comes out.


The problem could actually be simple and within your lines. Get a plunger and put it in the toilet, placing it directly over the toilet drain.

One thing people tend to do incorrectly with a plunger is being too gentle. When you get a good seal, give the plunger several good pushes to create a vacuum and potentially push a clog around. Doing this too gently won’t do much, if anything.

Tank cleaner

This is the second to last resort, though actually calling a plumber won’t likely be necessary unless there is something besides waste caught in your tank.

Tank cleaner contains enzymes and acids that literally at a clog at it’s source. This means that the tank cleaner will help dissolve mounds of toilet paper or solid waste.

You’ll want to wait a little longer with tank cleaner. Ice and hot water will begin to change temperature immediately, so draining earlier is OK. Wait a few hours if not overnight with tank cleaner to let it dig in.

RV owners can then dry to drain the black water tank. You should see some solid waste this time.

How to prevent a clogged tank

One of the biggest things you can do to prevent a clogged tank is to keep some freshwater in there when you maintain and drain your tanks. The dreaded “poop pyramid” is most often caused by having solid waste or excess toilet paper in an overly dry tank with no other liquid, including urine. Urine or water can help keep solid waste moist so it flows naturally and doesn’t stick to the tank or pile up.

The above also means using lots of water when you flush your toilet. A lower flo toilet might be contributing to the problem.

Filling your black water tank with some water can be quite helpful in this scenario.

Also, use RV friendly toilet paper. To be fair, there aren’t many toilet papers that are truly RV unfriendly, just be sure you are using the right kind.

Keep your black tank closed when not in use. This literally means that you should close your black tank valve right away after draining. Don’t store your RV with anything in the black water tank, either.


Your RV bathroom is a pretty convenient place to use the bathroom on the road. Thankfully, the bathroom is relatively easy to maintain though it’s different from your home toilet. The above advice has some easy methods like boiling water and ice, and some methods that need a hardware store trip like tank cleaner. You should clear out your tank occasionally anyway, but using tank cleaner will certainly work with a bit more effort and time.

Just keep water in your toilet tank and you shouldn’t run into many issues of having the tank clogged, as it’s most commonly caused by larger objects stuck in the tank, or overly dry waste.

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