(Image credit: Emil Evans)

Life is all about the details, but sometimes, those details aren't pleasant. If your toilet is running, you're potentially wasting gallons of water a day. But don't despair! Most often, it's just a simple fix, no tools — or plumber — required.

The first thing to understand is that toilets work on gravity. When you push down the lever it lifts up a rubber flapper, allowing water to run out of the tank and into the bowl. Once the water in the tank runs out, the flapper closes and allows the tank to fill again. The tank water then slowly rises until a float closes the intake.

(Image credit: Emil Evans)

To figure out which part of the toilet is leaking, take off the tank lid and identify your parts:

A: Toilet flush lever
B: Rubber flapper blocking the tank water from descending into the bowl. It is connected to the toilet flush lever above.
C: Pump which refills the tank after it empties.
D: Float which raises and lowers with the water level to tell the pump when to go and stop.
E: Overflow tube, what sets the high water level in the tank.

Note: the water in the tank is clean (unused); it's perfectly fine to stick your hands in the tank to pull out or adjust parts. Like any home repair, wash them when you're done.

This is the silver knob that turns on and off the flow of water to the toilet. Before you start, turn this off (all the way to the right.)
(Image credit: Emil Evans)

Before you do anything else, it's a good idea to turn off the water connecting to the toilet. This is easily accomplished by tightening the silver knob on the wall behind the toilet.

Common Cause #1: Problems with the Chain

(Image credit: Amazon)

Check the connection between the flush lever and the rubber flapper it's attached to. Jiggle the flush lever and watch the chain between it and the flapper. The chain is too short if it constantly pulls on the flapper even when the flush lever is at rest. If it's too long it might interfere with the flapper closing.

If there's extra length on the chain it's simple to move the clip down. Otherwise, just replace the chain with any aluminum ball chain or other small chain that's longer in length.

Tip: Some chains have floats attached (like the one above from Amazon). If there is a float on the flapper chain, make sure it's loosely floating on the surface or else it also may be pulling up on the flapper. If so, either move the float up on the chain or remove it.

Common Cause #2: Broken, Dirty or Warped Flapper

This rubber flapper is connected to the flush lever and is what opens and closes when you flush the toilet.  The two arms on the left are hooked in place to create a hinge for the rest to go up and down.
(Image credit: Emil Evans)

Over time, the flapper can warp or break at the hinge, and start to leak. To check on the flapper, first flush the toilet to drain the water out of the tank. Unhook the flapper from the base of the tank and pull it to the surface in order to get a closer look.

The bottom of the flapper.  If there are vertical lines of discoloration, it's probably warped and should be replaced.  This one looks good!
(Image credit: Emil Evans)

Turn the flapper over and look for any discoloration (which could be a sign the flapper is warped and needs to be replaced), mineral deposits, warping, or any breaks in the plastic or rubber.

First try cleaning off any buildup that might prevent the flapper from closing properly. Or, if you see a problem with the actual flapper, they are cheap and easy to replace. To switch it out, simply disconnect the old one from the chain and attach the new one. Then hook the new flapper back over the drain.

Tip: When buying a new flapper, make sure you get one that attaches to the chain on the thick center part, not the thin outer lip (where it's more likely to warp).

Common Cause #3: Float Position

This plastic balloon floats on the top of the water to tell the pump (left) when the tank is full. When full, the water level should be just below the top of the overflow pipe at the bottom center of the image.
(Image credit: Emil Evans)

When a toilet is flushed, the tank should stop filling when the water is just below the overflow pipe. If it goes over and the tank is still filling, then the float for the pump is too high. Test this by flushing the toilet a few times, and noting where the water stops.

The simplest fix is to bend the rod connecting the float to the pump so the float is lower and it will signal the pump to turn off sooner. If the arm won't bend, then it might be time to call in the tools...and the plumber.

So, next time you hear the sound of a leaky toilet, get in there, poke around, and see if you can identify the most likely problem. Chances are good you can figure it out, make the easy fix, and save money on a plumber!