Closeup on a toilet blowl with arrows pointing down, indicating a dropping water level.

If it takes more than one flush to clear waste from your toilet, its water level is low. How can you identify what is causing this problem, and what should you do to fix it? 

This article will cover the factors that can cause your toilet water level to drop randomly and highlight solutions you can implement to overcome this problem.

Let’s expiscate!

Why Does My Toilet Water Level Randomly Drop?

Your toilet water level can drop randomly if the fill pipe or valve is faulty. Blockages in the rim jets due to bacteria or mineral deposits can also cause this problem. Also, if anything obstructs the vent stack or your area is experiencing high-speed winds, it can affect the toilet’s water level.

So now that you’ve seen the big picture, let’s look closer at each of these culprits.

No Water Flowing From the Fill Pipe to the Overflow Tube

The fill valve is a crucial part of the toilet, which is responsible for loading the tank with water. At the same time, it also directs water toward the overflow tube. It does so by allowing the water to flow through the fill pipe. 

If you’re unfamiliar with how a toilet works, the overflow tube connects to the bowl. The water from the overflow tube enters the bowl and maintains the water level. 

So, if there’s barely any water flowing or no water flows from the fill pipe to the tube, your toilet water level may drop.

How To Fix

To understand whether the problem is with the fill pipe, you need to remove the toilet tank’s cover. In most toilets, it is easy to remove the lid as you can just pull and separate it from the tank.

However, removing the lid for models like the dual flush toilet involves an extra step. First, you must remove the buttons (flush) using a flat-head screwdriver. This procedure will reveal the screw you must unscrew before removing the casing holding the buttons.

If you find this confusing, you can watch this video breaking down the whole process of removing and reinstalling the tank lid:

Screenshot from a video video breaking down the whole process of removing and reinstalling a toilet tank lid.
Courtesy of Billshowto

Once you’ve taken off the toilet lid, follow these steps:

  1. Locate the fill pipe, which starts from the fill valve and ends inside the overflow tube – remove it from the overflow tube and flush the toilet. When the tank refills, check if water comes from the fill pipe.
  2. You’ll need to replace the fill valve if there is no water – this process is relatively easy as you don’t need to be a plumbing expert. First, find the same fill valve model as the one in your toilet. Before you replace this part, make sure you turn off the toilet’s water supply. 
  3. Flush the toilet to clear out all the water from the tank – place a bucket below the tank to catch any excess water in the fill valve. Remove the fill valve and replace it with a new one, and you’re good to go.

If you feel uncomfortable with this do-it-yourself (DIY) solution, you can contact a professional plumber to do the whole process.

Strong Winds or a Storm Outside

Strong winds, especially during a storm, will affect your toilet water level because of how toilets and plumbing systems are designed. Generally, your plumbing system will have vents. 

When you flush the toilet, the water will go down the drain pipes. At this moment, the water will try to pull down air provided by the vents.  

These days, toilets come with a plumbing trap in the pipes, which prevents sewer gas from entering the toilet and gives your bathroom a foul smell. The plumbing trap is a clever pipe design that retains a particular volume of water.

When your area is experiencing strong winds, air will enter the vent forcefully. Not only will this disturb the water in the toilet, but it also forces it to start draining from the bowl.

How To Fix

Unfortunately, there is no way to fix this problem. You’ll need to wait for the storm or strong winds to stop or settle down for the toilet water level to normalize in the bowl. Also, you’ll have to flush once after the strong winds or storm to restore the water level.

The Fill Valve Is Faulty or Set Up Incorrectly

If the toilet water level is low, it can be due to the fill valve. Any problems with this part, like leaks or cracks in the housing, will cause issues. 

The fill valve will have a float, which tells it when to start and stop filling the water in the tank. If water leaks from this component, an inadequate volume of water will go toward the overflow tube, decreasing the water level. Also, there won’t be sufficient pressure for water to flow to the fill tube consistently.

If there aren’t any flaws with the fill valve, it’s possible that it wasn’t set up properly after installation. 

Every fill valve will have a screw, which you can turn to increase or decrease the water level in the toilet’s tank. First, open the tank and look for the manufacturer’s recommended water level. It will be indicated either on the tank itself or the overflow tube.

How To Fix

Ideally, when you flush, the water will fill up to a certain height before cutting off the water supply to the tank. However, if it is lower than the recommended level, you need to adjust the fill valve. For this, you’ll need a flat-head screwdriver.

Locate the screw and turn it clockwise to increase the water level in the tank. Doing so will also raise the water level in the toilet bowl. Then, flush the toilet to see how much you’ve increased the water height in the tank.

Illustrated image demonstrating how to increase the water level in the toilet tank
Courtesy of wikiHow

While you can increase the toilet water level beyond the manufacturer’s recommendation, you should avoid this practice. In most cases, the excess water will enter the bowl. Also, some of this water will exit via the drain, wasting precious resources.

If there is visible damage on the fill valve and it leaks, you’ll need to replace this part. When ordering this component, ensure it is the same size as the previous one. Otherwise, it won’t fit inside the tank.

The Vent Stack Is Blocked

As highlighted earlier, vents are crucial when draining water from the plumbing system. If there is some blockage in the vent, e.g., plant debris or an animal or bird has built a nest inside the pipe, it will affect the toilet water level.

You can test whether the vent is clogged in your bathroom. Turn on the tap in the sink or the shower and see if it changes the toilet’s water level. If it goes down, it indicates something is blocking the vent.

Another way to test the vent is to flush the toilet. Does the water bubble when the toilet bowl gets refilled? Or does it take a long time for the water to drain from the bowl? You must check the vent if the answer is yes to either of these questions.

How To Fix

The solution is simple: Locate the vent and remove the clog. If you can’t find anything, you must contact a plumber. They will have the necessary tools to remove the blockage, especially if it is deep inside the pipe network.

A plumber working on a toilet in a bathroom

Once you’ve removed the clog, we recommend installing a filter on the vent. Also, you should check on it regularly to keep it free from debris.

Mineral Deposits or Bacteria Are Clogging the Rim Jets

When you flush the toilet, you’ll notice water coming from the bowl’s top. There are openings in this part of the toilet, known as rim jets. 

Unfortunately, the size of these gaps makes it easy to get blocked. 

The clog can happen due to the following reasons:

  • Your household receives hard water – as a result, there are mineral deposits on the rim jets. Over time, the thickness of these deposits increases, blocking the openings.
  • Bacteria growing inside the rim jets – bacteria growth can happen if you haven’t used the toilet for a while.

Before taking action, you must ensure something is blocking the rim jets. You can use a small hand-held mirror, like a dentist’s mirror, to look at these openings. If there are white or light-colored deposits or dark spots, it is a clear sign of a clog.

How To Fix

You’ll need the following to remove the blockage:

  • White vinegar
  • Brush with plastic bristles

Although you can use a brush with metal bristles, the problem is that it will leave scratches on the porcelain. 

A gloved hand scrubbing a toilet bowl

Here’s how you can fix this problem with the rim jets:

  1. Open the toilet tank’s lid and locate the overflow tube.
  2. Next, heat the white vinegar until it starts boiling
  3. Transfer it to another container and pour the white vinegar into the overflow tube.
  4. Wait at least an hour for the white vinegar to work its magic. You can pour white vinegar and wait overnight if there is heavy build-up.
  5. Use the brush to scrape the mineral deposits or bacterial growth off the rim jets.
  6. Finally, flush the toilet and check whether the toilet water level in the bowl goes back to its original height.

If there are excessive mineral deposits in the rim jets, you’ll need something more substantial than white vinegar. Any toilet descaler solution will suffice, and you can follow the same steps listed above.

If the hot white vinegar didn’t remove the bacterial growth, you’d need to use bleach. However, since you’ve used vinegar, you should wait at least a day before adding bleach to the overflow tube because bleach and vinegar together can create harmful gases that are extremely dangerous. Also, use the toilet regularly to flush out any remaining vinegar. 

For white porcelain, bleach won’t be a problem. However, if you have colored porcelain, we recommend sticking to liquid oxygen-based bleaches, which won’t damage the toilet’s tone. 

Pour the bleach solution into the overflow tube. As bleach is a harsh chemical, don’t wait more than 10-15 minutes after adding it to the toilet. Use the brush to remove any residual bacteria from the rim jets, and flush the toilet to remove the bleach solution and bacteria. 

A Crack in the Toilet Bowl or Piping

If you’ve tried all the above solutions, there may be a crack in the toilet bowl or piping that’s causing the toilet water level to drop. 

You can check for this by placing toilet paper on the floor around the toilet. Wait an hour and see if it is wet. You’ll need to replace the entire unit if there are cracks in the housing. For leaks, it is possible to seal them. In any case, we recommend contacting a licensed plumber to help you out.

Leaks in the bathroom can be expensive. To learn more, you should check out this article.

Final Thoughts

There are five possible reasons why your toilet water level is low. Most of these issues are easy to fix on your own. However, you can contact a licensed plumber if you’re uncomfortable making DIY repairs or need to replace the toilet.

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