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RV Black Tank Shows Full When Empty? (4 Reasons) How to Fix

You probably don’t give your RV black tank sensors much thought – that is, until they start misbehaving. After all, there’s nothing glamorous about your RV’s black tank sensor. But as any seasoned RVer knows, it’s a vital part of keeping your rig in good working order.

If your black water tank shows full when it is empty, it could be one of four reasons. The sensor could have built up debris, preventing an accurate reading. The tank could also have a pressure build-up because of clogged vents. You could also have a wiring issue or a faulty black tank sensor.

rv black tank sensor

The black tank sensor lets you know when your black tank is full to avoid unpleasant surprises. However, sometimes the sensor can give false readings, indicating that the tank is full when it is empty.

In this article, we’ll discuss why your sensors might show full when empty, how to resolve the issue, and how to prevent it from happening again.

Why Does My Black Water Tank Show Full When Empty? 4 Reasons

If you’ve ever gone to flush your black tank and met with a full sensor reading, you know the feeling of frustration. While it’s tempting to believe that your tank is somehow defying the laws of physics, the reality is often much more mundane.

Here are the reasons why your black tank sensors show full when empty.

1. Dirt and Debris

The most likely explanation is that debris and dirt have built up on the sensor, preventing it from accurately measuring the level of waste in the tank. 

The good news is that you can fix this problem by cleaning the sensor with a brush or cloth. So if your black tank sensor is giving you false readings, don’t panic – give it a good cleaning, and you should be back in business in no time.

Encrusted sensors will commonly read 2/3 full, even immediately after dumping. To fix this problem, you can use an enzyme packet (like Commando tank treatment) to dissolve residue and restore sensor function.

2. Clogged Vents

If your RV black tank sensor displays a full tank when it is empty, one of the reasons could be that the black tank vent pipe is clogged.

When this happens, it causes a buildup of pressure in the tank, which trick the sensor. Check the vent pipe for any blockages if you have a falsely full black tank.

And if you’re feeling particularly adventurous, you can try to unclog it yourself. Remember to wear gloves and a mask – you don’t want to breathe in any of that!

3. Wiring Issue

One possible reason for this is a wiring issue. If the wires are loose or damaged, they may not be able to send an accurate signal to the sensor. 

Regularly inspecting your RV’s black tank sensor and ensuring the wires are in good condition can help ensure that you’ll always know when it’s time to empty the tank.

4. Faulty Sensors

In many cases, the problem stems from a faulty sensor. Over time, RV black tank sensors can become clogged with debris or stop working properly. As a result, they may give false readings that make it seem like your tank is full when it’s empty.

If you suspect that your sensor is to blame, the best course of action is to have it replaced by a qualified technician. With a functioning sensor, you’ll make better use of your black tank and enjoy a hassle-free camping experience.

my black water tank shows full when empty

4 Signs Your Black Water Tank is Clogged

If you’ve ever gone camping, you know the importance of a clean black water tank. It is gross to have a clogged tank, but it can also lead to serious health hazards.

Here are a few signs that your black water tank needs a thorough cleaning:

  1. The toilet won’t flush: This is usually the first sign that something is wrong. If the toilet won’t flush, it’s likely because the black water tank is full, and you’ve to empty it.
  2. The drains are slow: If your drains take longer than usual, it could be because the black water tank has debris, so you’ve to clean it up.
  3. There’s an odor: This one is pretty self-explanatory. If your RV has an unpleasant odor, it’s likely because the black water tank is full and needs emptying.
  4. The tanks are full: If you’ve been emptying your tanks more frequently than usual, it’s likely because they’re clogged and need cleaning.

Did you forget to dump your black water tank before returning home? Here’s how to dump RV waste at home.

Can You Clean Your RV Black Tank With Baking Soda?

Many people swear by using baking soda to clean their RV black tanks. After all, it’s a cheap and readily available option that is also gentle on the environment. But does it work? The short answer is yes. 

However, it is not a magic solution. Baking soda will not completely break down toilet paper or other solid waste and will not eliminate the need to dump your tank periodically. Nonetheless, it can help to reduce odors and keep your tank clean. 

How to sanitize your RV fresh water tank.

The Verdict

As any RVer knows, keeping the black water tank clean is essential for a comfortable and enjoyable trip. However, even with the best intentions, the tank sensors can sometimes become clogged with buildup. If this happens, don’t despair! Clearing the sensors is a relatively simple task that you can do using an approved tank cleaner.

Just follow the instructions carefully, and your sensors will function properly. And remember, proper maintenance and treatment of your black water tank will help to prevent sensor clogs in the future.