How to Repair a Running Toilet [Video]

With a little know-how, you can find out what causes a toilet to run and fix it, saving the expense of a costly professional repair.


Sooner or later, virtually every household will have a leaky toilet that keeps running. You may notice water drips or just hear it constantly refilling. This is not only annoying, it’s wasteful and expensive. Even a moderate toilet leak can waste 6,000 gallons of water a month, adding hundreds of dollars to your annual water bill.

Fortunately, with a little know-how, you can find out what causes a toilet to run and fix it, saving the expense of a costly professional repair.

Before you begin, make sure there's sufficient water pressure in the toilet tank for efficient operation. Water flows to the toilet through a small valve on the wall or floor behind the toilet. Turn the valve counterclockwise to the full “on” position to maintain proper water pressure while you are checking for leaks.

The most likely causes for a running toilet are the flapper or flapper chain, the fill tube or the fill valve and float. You may need to check them all to find the source of the problem.

Flapper and Flapper Chain

Open the toilet tank and check the chain attaching the flapper to the flush mechanism. The flapper is the rubber stopper that lifts up during the flush, allowing water to flow from tank to bowl. If the chain is too loose, the slack part of the chain can get between the flapper and the rim of the flush valve, preventing the flapper from sealing properly. If the chain is too tight, the flapper can’t fully seal onto the flush valve. You may need to experiment to get the right amount of tension in the chain.

Check the flapper itself. Over time, the flapper’s rim can corrode or deteriorate and fail to seal properly. If this is the case, remove the old flapper and buy a new one at your hardware store. Attach the new flapper to your flush mechanism and make sure it is sealing properly as the tank fills with water.

Fill Tube

Check this small plastic tube running from the toilet tank’s fill valve into its vertical overflow tube. If the end of the tube is under water, cut it back so that the tube clears the water level.

If the toilet handle remains stuck in the downward position after you flush, you may also need to replace the lever mechanism.

Fill Valve and Float

Check the water level in the tank. It should be half-inch to one inch below the rim of the vertical overflow tube. If the water level is too high, adjust the float mechanism. If the water level is too low, there will not be enough water pressure for the toilet to operate properly.

Older toilets have a ball float that controls the fill valve. If the ball floats too high, the water rises above the overflow tube, and the tank never stops draining. A quick fix is to bend the arm of the ball float downward to reduce the flow. You can also adjust the float by turning the screw that attaches the float arm to the fill valve.

In newer toilets, the float assembly may be part of the fill valve. Depending on the type of valve and float you have, you can adjust the float using a screw on top of the float or a clip on the adjustment rod.

If your toilet is still running after checking the water level and adjusting the float, you may need to replace the fill valve. Turn off the water supply, flush and drain the tank and free the valve by unscrewing the water supply line outside the tank. Take the old valve to the hardware store to make sure you’re buying the right replacement. Attach the new valve and adjust the float to the desired water level.

If your toilet is still running constantly after replacing bad parts or making adjustments, the problem may not be water pressure. A clogged toilet could be the culprit. Use a nylon brush to clear away any clogs and increase your toilet’s flush performance.

Repairing a running toilet on your own requires a little time and patience (and possibly a visit or two to the hardware store), but the savings and satisfaction are worth the effort.


AHS assumes no responsibility, and specifically disclaims all liability, for your use of any and all information contained herein.

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