How To Adjust the Water Level in a Toilet Bowl

Learn about correct toilet water levels, why they're important and how to adjust them yourself.

It can be easy to overlook the water level as a possible culprit for a problematic toilet. In reality, water levels play a crucial role in the proper functioning of this hard-working bathroom fixture.

If your toilet’s flushing power has been less than optimal lately, it may be time to take a closer look at the water level. With the help of licensed plumbers Alexander Siv and Jason Duda, we’ll explore the significance of toilet bowl water levels, potential issues if they’re too high or low, and some easy DIY fixes to get your toilet back to working as it should.

Why Is Toilet Bowl Water Level Important?

Every toilet has an optimum water level established by the manufacturer. Keeping the right water level is essential for your toilet’s proper functioning, cleanliness and cost-effectiveness.

“It’s very important to set the water level exactly where the manufacturer engineered it to avoid any problems,” Siv says, “It’s how they are designed to work properly.”

The manufacturer’s level should be on the overflow valve or the inside of the tank, Siv says. If there isn’t a line, in general it should be 1/2- to 1-inch from the top of the overflow tube.

Low water levels

Low toilet water can cause weak flushing pressure, leading to clogs and inefficient waste removal in the trapway or drain. “You need to have enough water in the tank and the bowl to create the flush pressure to remove what’s in the bowl,” Siv says.

Water in the bowl creates a barrier against sewer gasses. If it’s too low, these unpleasant smells can permeate the room.

Proper water levels also prevent stains and mineral buildup in the bowl, and waste and minerals from adhering to the porcelain finish.

High water levels

If the water level is too high, you run the risk of the toilet overflowing when it’s flushed. The toilet bowl is designed to have a certain amount in it, and excess water can overwhelm the system.

Higher than necessary toilet bowl water levels also wastewater and lead to higher utility bills.

Identifying a Water Level Problem

The optimal water level for your toilet depends on the toilet itself but should range from one-third to half full. “Each manufacturer engineers their toilet system to work the way they engineered it,” Siv says. “So each manufacturer will have more or less water in their bowl to get the flush that it needs.”

However, if your toilet bowl water level is suddenly different, it can be a sign that something is wrong.

Be on the lookout for other toilet flush changes as well. “The toilet will either start taking forever to refill or the valve is leaking, so there will be less water in the bowl,” Siv says, “This can indicate it’s time to replace the fill valve.”

Water levels that are too low can indicate a leak, issues with the fill valve or a drain clog. Water levels that are too high can also be a sign of a faulty fill valve or clog in the line. Both can mean your water levels simply need to be adjusted.

How To Raise or Lower the Water Level in a Toilet

If your toilet tank is filling to the manufacturer’s fill line, the water in the bowl should be the correct level, too.

If, however, you find that your toilet tank is below or above the manufacturer’s fill line, adjust the tank water, which will adjust the bowl water level.

“How you adjust water levels in the tank and bowl is determined by your fill valve type,” Duda says.

Fill valves are generally one of two types:

  • Ball float valve: A ball attached to a metal arm regulates water levels in the toilet tank as it moves.
  • Float cup valve: A plastic cup connected to the valve shaft dictates water levels as it rises and falls.

Remove the tank lid, and follow these adjustment steps for each valve type.

Ball float adjustment

To adjust a ball float, you’ll need a flathead screwdriver. Locate the toilet valve shaft, typically on the left side of the tank. “Look for a screw head on the valve that controls the float and that controls the water level,” Siv says. Adjust the water level by turning the screw clockwise to lower the ball or counter-clockwise to raise it.

Only turn the screw one rotation at a time, then flush the toilet to see if it works efficiently.

Float cup adjustment

“If it is a float cup fill valve, there’s an adjuster, usually on the valve arm, that can be turned clockwise or counter-clockwise,” Duda says. “This adjusts how high the water level goes before the fill valve shuts off.”

Use a Phillips head screwdriver to turn the plastic adjuster or turn by hand. Check water levels when finished and fine-tune as needed. Then replace the tank lid.

How To Keep the Water Level Where It Belongs

By being vigilant, performing regular maintenance and addressing issues promptly, you can maintain the proper water level in your toilet.

Follow these steps.

  • Regularly check for leaks:¬†Look inside the tank and around the base.
  • Check tank water levels: Inside the tank, adjust the fill valve to ensure the water level is around one inch below the rim of the overflow tube or at the manufacturer’s fill line.
  • Replace faulty fill valves: If you notice persistent issues with the water level, consider replacing worn-out or damaged fill valves.
  • Remove clogs: Promptly address clogs in the toilet trapway or drain with a plunger or toilet auger.

About the Experts

Alexander Siv is the owner of Amherst Plumbing and Heating in Amherst, Massachusetts. He has a master plumber’s license in Massachusetts and more than 10 years of experience.

Jason Duda is the manager of Boulanger’s Plumbing and Heating in Easthampton, Massachusetts. He has a master plumber’s license in Massachusetts, New York and Virginia with more than 25 years of experience.

Laurie M Nichols
Laurie M. Nichols is a registered contractor in the State of Massachusetts and owner of a home repair business since 2016. Through her business, Laurie has encountered and fixed most home related problems for hundreds of customers. Her skills include carpentry, drywall, tile, painting, flooring, plaster repair and wallpapering. Laurie is also a DIY real estate investor who buys, renovates and rents multifamily properties. Through this venture she has developed creativity in frugal home repair and renovation as well as design. Much of Laurie's writing for Family Handyman is informed by her personal and professional experience, but she also enjoys researching and writing about any home topic, and connecting with fellow pros when necessary, too.