Why Is There A Low Water Level In The Toilet Bowl?

Although the amount of water in your toilet bowl can seem unimportant, it's actually something you need to keep a careful eye on. Low water in the toilet bowl acts as a warning sign that your toilet or plumbing system might be damaged. In other cases, it already causes certain plumbing issues, like preventing the toilet bowl from completely flushing.

The water also helps remove smells from the bathroom, so when the toilet water levels are low — you might encounter foul smells like sewer gas. To prevent issues from arising,  here are the most common reasons for low water in a toilet bowl and how to fix any of these problems.

low water in toilet bowl

Degraded Fill Tube

The fill tube is a small plastic hose. It connects to a plastic tube inside the toilet tank called the overflow tube. When working correctly, the fill tube allows water to flow into the bowl with each flush.

The fill tube can degrade over time or even unclip from the overflow tube. If the fill tube has a problem, it can trick the fill valve into shutting off the water flow too early after flushing, resulting in too little water in the bowl. Fill tube problems are the most common cause of low water in toilet bowls.

Fixing an issue with the fill tube is usually simple. If the tube has shifted out of the correct location, you can snap it back into place without much of a hassle. Replacing a worn or damaged fill tube is also quick and easy. Sometimes, it's also better to just invest in an anti-clog toilet to avoid future issues.

Blocked Sewer Vent Line

The sewer vent line runs from your bathroom to the exterior of your home. It allows sewer gases to escape safely when you flush the toilet.

Blockage in the sewer vent line can result in small amounts of water in the bowl. Anything can potentially block the line from outside, such as leaves, branches, and other outside debris.

To identify a blocked sewer vent line, you'll need to physically examine it. A snake is often the most helpful tool for removing the blockage. You'll need to get on the roof and analyze the situation before using your tool to remove things.

Cracked Bowl

cracked toilet bowl

Cracked toilet bowls aren't common but can be an issue, especially with older toilets. If the porcelain cracks, toilet water can leak out, resulting in low amounts.

Sometimes, a cracked toilet bowl is obvious. You'll see a line in the porcelain and water on the floor. However, other cracks aren't as apparent. A small gap could result in water leaking internally, which can have more indirect signs, such as water stains on the ceiling of a lower floor.

If your toilet has a crack, there are two options available. You can either seal the crack or replace the toilet. Sealing cracked porcelain requires a moderate amount of repair know-how but can end up cheaper than buying a completely new toilet bowl.

Never ignore any cracks in the porcelain of your toilet, as they will only grow worse with time.


Certain types of clogs can lower the water level in a toilet. A traditional clog in the internal piping causes water levels to rise too high. Water spills over the edge of the toilet onto the bathroom floor. While this type of clog is an issue you'll need to deal with immediately, it won't result in low water levels.

However, there's another type of clog that can drop water levels. In this situation, the blockage siphons water away from the bowl.

Flush the toilet and watch what happens. A partial clog is likely responsible if the water rises to the top of the toilet, almost to the point of overflowing, only to drop below normal water levels.

To remove the clog, you have a few options. A plunger is usually the simplest solution, but it might not work if the blockage is located deep inside the pipes. If a plunger doesn't work, try using a snake with a longer reach.

Clogged Inlet Holes

Also called rim jets, inlet holes are the tiny holes found underneath the toilet rim. They allow water to flow from the tank into the toilet bowl and start the flush cycle. The inlet holes are also angled to create a circular water flow, making flushing more effective.

If the inlet holes become clogged, the water level in the toilet will drop. The most common type of clog is due to calcium buildup, which can occur due to the mineral composition of the hard water in your area. This is why it’s essential to routinely clean the toilet rim.

You should watch signs like a toilet failing to flush completely, water flowing slowly, diagonal water flow turning vertical, and orange or black spots on the inlet holes.

Fortunately, removing calcium buildup is usually simple. Pour hot vinegar into the toilet tank through the overflow tube. Allow the vinegar to sit in the toilet for several hours.

Vinegar will loosen and remove the bulk of the calcium build-up. To get rid of anything that remains, use a small wire, such as a straightened hanger, to poke into the holes. Then, scrub each inlet with a small brush.

Final Thoughts

Low water in a toilet bowl often indicates a problem with your toilet or plumbing. It's important always to note any changes in the toilet’s water level and determine the cause. Fortunately, by following the guidelines outlined above, you can keep your toilet and plumbing system in optimum condition.   

If you find that none of these methods have worked for you, make sure to call a licensed plumber who can help figure out the source of your plumbing problems. 

About the author 

Ryan Thompson is a residential and commercial plumber from Miami, Florida. He has over 20+ years of plumbing experience. He is also a huge DIY enthusiast who does all types of improvement projects around the house.

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