How to Unclog RV Black Water Tank?

One appeal of RV travel is the convenience of having a toilet on hand. What’s not often discussed is how intimate RVers become with their waste. An RV black water tank facilitates a mobile toilet and learning how to care for one is part of the RV lifestyle. 

RV owners can unclog an RV black water tank by breaking down the buildup and flushing it out. The location of the clog determines whether a home solution, chemical treatment, or manual labor will clear it best. Regular tank maintenance and good practices then reduce buildup and prevent future clogs.

A clogged black water tank can lead to bad smells, leaks, and costly repairs. By understanding how the waste system works, we can determine the proper steps to take. Let’s take a look at what you need to know to unclog an RV black water tank. 

What Is an RV Black Water Tank?

A black water tank is an on-board waste receptacle that allows an RV toilet to function while not connected to a septic system. Everything that gets flushed down the toilet is led through a pipe into the black water tank that sits in the underside of the RV carriage. 

Waste will sit and collect in the black water tank as you travel, keeping your RV mobile. When you’re hooked up to a dumping facility, a lever on the outside of the RV will release the gate valve and allow waste to flow through the attached hose and into the septic tank. 

How to Unclog RV Black Water Tank?

Dealing with black water tanks can be a dirty business, so it’s important to have the right tools on hand.

Here is a step-by-step approach to unclog an RV black water tank as efficiently as possible. 

Step 1: Prepare for the Task

Before you begin, be sure to grab the proper supplies. These should include:

  • Latex gloves
  • Protective eyewear
  • A towel or paper towels (optional)

Disposable gloves and protective eyewear are non-negotiable safety measures when dealing with feces or chemicals. Towels may or may not be necessary, but it’s wise to keep something to wipe with on-hand as well. 

Step 2: Determine Where the Clog Is

Determining where the clog is in your waste system will help you choose the best method to clear it. 

If you suspect a clog in your RV black water tank, the first place to check is the gate valve. Open the valve with the sewage hose connected to a dumping receptacle and with the black water tank partially full. If nothing comes out, then the clog is likely right behind the valve, preventing it from opening properly. 

It is possible to open the valve manually to remove the clog, but any additional black water will pour out behind it. This is not sanitary for you, nor is it sanitary for the surrounding environment that it may spill onto. Instead, it is best to use a treatment to break up the clog within the tank. 

A clog may also occur before it ever reaches the black water tank. If the gate valve seems to be working properly, take a look down the toilet. The pipe through which waste passes from the toilet into the black water tank can collect waste in mounds called pyramid plugs. These can usually be seen by opening the toilet valve and shining a light down into the pipe, and they may require some manual work to be removed. 

Step3: Remove the Clog

There are several ways to go about removing a clog depending on where and how stubborn it is. We’ll begin with the easiest and progress from there. 

Break Down and Remove Buildup

Clogs occur because of buildup, so the first step is to break down that buildup. There are three popular methods to try first.

  1. The Liquid Soap Method

Pour a generous amount of liquid laundry soap down the toilet and into your black water tank and fill the tank about half-full with water. Then take your RV for a drive—the bumpier, the better. 

The goal here is to knock off and disintegrate any build-up and clogs within the blackwater tank. After driving, let the tank soak for a few hours before flushing the debris out.

  1. The Ice Cube Method 

Fill your black water tank approximately 1/3 full with water, then fill the rest with ice. Take your RV for a bumpy drive to break down clogs, then flush them out afterward.  

  1. Chemical Treatment

There are many chemical treatments made to remove clogs and buildup in RV black water tanks. Each works a bit differently, so be sure to follow product directions.  

Manually Remove Buildup

If the clog is due to pyramid plugs that did not break down with any of the above methods, you’ll have to manually remove them with an auger. 

An auger is a type of toilet snake that will scrape the sides of the pipe to dislodge buildup. It is recommended to get a manual auger to avoid accidentally doing damage to your black water tank.  

Call a Pro

If the clog persists or if your stomach is not holding up, it may be time to call in some reinforcements. Although professional service will cost more than the above methods, they can save you on time and from getting your hands dirty.  

RV Black Water Tank Maintenance 

Unclogging a black water tank can be a hassle, but regular maintenance can help you avoid it. Use the following maintenance tips to avoid clogs and prevent buildup in your RV black water tank.

  • Only flush waste and septic-safe toilet paper. Anything else will not break down and may get stuck and cause clogs. Keep a small trash can next to the toilet for any other items to be disposed of. 
  • Regularly use a black water tank treatment. They come in liquid, powder, and pod form and should be used monthly or each time the tank is emptied. 
  • Always leave the black water tank valve closed when connected to a dumping facility. Rather than leaving the valve open and taking the risk of more solid waste getting stuck and drying along the way, it is best for liquid and solid waste to collect and puddle up, then flush out together as one big mass. 

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