A toilet that keeps running can drive up your water bill, in addition to the constant noise. The good news is that most issues come down to two items: the flapper and the fill valve.

You can easily replace each one by following the steps outlined below. The first step is to diagnose which item needs to be replaced.

In general, if the toilet is running infrequently, replace the flapper. If it’s running continuously, replace the fill valve.

To confirm your diagnosis, turn off the water to the toilet. The water can be turned off at the valve where the supply line comes out of the wall or floor. Turn the valve clockwise to turn off the water.

Once you turn the water off, if the tank starts to empty out, it’s the flapper that needs to be replaced. If the toilet stops running as soon as you turn the water off, it’s the fill valve that needs to be replaced.

Now that you know which item to replace, let’s walk through the steps:

How to replace the toilet flapper:

The toilet flapper is easy to replace. They come in two sizes, two or three inches, and you can find them at any home retail store. In general, older toilets use a two inch flapper, and newer ones use a three inch one. If you’re still not sure, just measure the current one before buying a new one.

Once you have the new flapper, here’s how to replace it.

1. Turn off the water to the toilet. 

This is where the supply line comes out of the wall or floor. Turn the valve clockwise.

2. Empty the tank by flushing the toilet. 

You can hold down the flush handle to drain as much water as possible.

3. Observe how the current flapper is installed. 

The best way to ensure you know how to install the new flapper is to look at how the current one is installed, especially the length of the chain or lift rod.

Go ahead and remove the current flapper.

4. Clean the seal area with a cloth. 

The old flapper might just be worn out, but there could still be residue at the seal area preventing it from closing. Wipe down the area with a cloth.

5. Install the new flapper. 

Be sure the new flapper closes completely and that the chain is relaxed with a little slack.

Test it out by turning the water back on and flushing the toilet a few times.

Now let’s review how to replace the toilet fill valve:

Replacing the toilet fill valve requires a few more steps than replacing the flapper, but you can do it by following the steps below.

Finding a replacement fill valve is easy since nearly all toilets use the same type. Just select a universal fill valve at your home retail store.

1. Turn off the water to the toilet. 

This is where the supply line comes out of the wall or floor. Turn the valve clockwise.

2. Empty the tank by flushing the toilet. 

You can hold down the flush handle to drain as much water as possible.

3. Remove any remaining water with a sponge. 

You want to remove as much water as possible. When you remove the fill valve in a few steps, you will create a hole in the toilet that will empty any remaining water on the floor. You can wring the sponge out in the toilet bowl.

4. Disconnect the fill tube and the supply line.  

The fill tube connects to the overflow tube in the tank. It’s usually attached with a clip. The supply line is where the water line enters the toilet on the bottom left side on the outside of the tank.

5. Remove the old fill valve. 

In the same location as the supply line on the outside of the tank, unscrew the valve nut on the fill valve.

This is what connects the fill valve to the toilet tank.

6. Install the new fill valve. 

Tighten the valve nut on the outside of the tank until it’s snug. Consult the instructions that came with the fill valve and adjust the valve with the threaded screw on the side to achieve the correct water level in the tank.

7. Reconnect the supply line and the fill tube. 

Now you can turn the water back on and test out the fill valve a few times.