How to Replace a Toilet Flapper

One of the most common (and annoying) problems with a standard toilet, commonly known as a gravity-flush toilet, is when the fixture continues to run after the flush cycle is complete. Not only is the constant sound of trickling water irritating, but it can waste hundreds of gallons of water if you're not careful. When looking to solve this issue, turn your attention to your toilet flapper.

Anatomy of a Gravity-Flush Toilet

A standard gravity-flush toilet is remarkably simple in design, but having a good knowledge of its mechanism will help you understand what can go wrong. In many cases, you should be able to fix many problems without enlisting the help of a professional plumber. A gravity-flush toilet consists of the following parts:

Fill Valve

Also known as the ballcock or water supply valve, the fill valve is what delivers fresh water into the tank. The fill valve has a built-in float device that controls the water flow, opening when the water level in the tank drops, and closing when the water level is once again near the top of the tank. 

Toilet Tank

The toilet tank serves as a reservoir for the water that will be released downward when a flush cycle is initiated. 

Flush Valve

A flush valve is the opening at the bottom of the tank that connects to the toilet bowl. The flush itself occurs when water stored in the tank is released downward through the flush valve. The flush valve unit is integrated with the overflow tube and serves as a mounting point for the flapper. 

Flapper

Lifting the flapper initiates the flush cycle, allowing water to rush into the toilet bowl. When the flapper drops back into place as the flush concludes, the tank can begin to refill with water. 

Handle and Lever

This manually operated lever connects to a lift chain that lifts the flapper away from the flush valve when the toilet is flushed. 

Overflow Tube

As part of the flush valve unit, the overflow tube serves two functions. First, it provides an escape route for excess water to drain down into the bowl should the fill valve fail to shut off. Second, it allows a small stream of water delivered by a refill tube from the fill valve to flow down into the toilet tank. This small stream of water refills the standing water level in the toilet bowl. 

Toilet Bowl and Trap

The toilet bowl is integrated with a loop-shaped trap built into the body of the toilet. Together, this configuration holds standing water that seals off the sewer system from the bathroom. During the flush cycle, water and waste material in the bowl pushes through the trap and into the drain pipes. 

Diagnosing a Running Toilet

When a toilet continues to run after you flush it, there are several possible causes. Start with simple observation. If you take the cover off the tank of your toilet and peer inside, you'll notice a component down in the bottom: a hinged flap valve made of plastic and soft rubber (usually black or red) that is connected to the chain hanging down from the flush handle lever. This component is known as the flapper.

If you flush the toilet, you'll see that the chain lifts up the flapper, allowing water to rush down into the bowl. This initiates the flush cycle. As the water empties from the tank, the flapper drops back down like a trap door, closing the valve so that the tank can refill for the next flush. 

When a toilet continues to run after a flush cycle, it's usually because the flapper fails to seat itself properly back over the flush valve opening, allowing water to continue to flow into the bowl. In turn, the fill valve keeps pumping water as it continues its attempt to refill the tank. While sometimes there are adjustments you can make to the flapper, often the problem occurs because the rubber of the flapper hardens or softens over time and can no longer seal the valve properly. The solution is to replace the flapper with a new one.