Noisy toilet when filling up

Updated February 21, 2017

A noisy toilet flushed in the middle of the night can wake up the entire household. Not only that, it may be causing your toilet to use too much water, wasting this resource as well as raising your utility bills. With a little basic knowledge, this problem can be corrected without the need to call in a plumber.

Toilet Operation

Toilets must draw water from your home's plumbing system to operate. They do this through a fixture called a fill valve, which is mounted inside the toilet tank. A rod is connected to the tank handle, which in turn connects a chain to a toilet flapper. The flush cycle begins when the handle is pressed, lifting the rod and, in turn, the flapper. The flapper releases the water inside the tank, where it flows under the force of gravity into the bowl and carries away the waste inside into the sewer flange beneath the toilet. Fresh water then flows into the tank through the fill valve.

How a Fill Valve Works

The fill valve helps maintain a constant level of water inside the tank. The underside of the fill valve connects to the water inlet hose. The top of the fill valve is connected to device called a float. The fill valve and float assembly sometimes is referred to as the "ballcock". The float is buoyant and rises with the water level inside the tank. When the float reaches the proper level, it cuts off the fill valve, preventing more water from entering the tank. The fill valves cause the most noise inside a toilet tank, so, when investigating a noisy toilet tank, this is the best place to start.

Working With Toilets

Because toilet tanks are filled with water, they can be difficult to work inside. Empty the tank before starting work by shutting off the water supply valve, which usually is found on the floor or wall underneath the toilet. Turn the supply knob to the right to cut off the water. Water inside a toilet tank can be emptied by flushing the valve. Because the water supply has been shut off, the toilet won't refill.

Malfunctioning Fill Valve

The body of the fill valve is connected to other components in two places: the inlet hose underneath the tank and the float assembly. Some newer fill valves feature an integrated float assembly that does not need to be disconnected before the fill valve can be removed. The ball float at the top of a fill valve usually is held in place by a thumbscrew assembly. A retaining ring holds the fill valve body in place from the underside of the tank. This must be removed before the fill valve can be extracted. If the fill valve is constantly running, it should be replaced. Because of various anti-siphon plumbing codes, it's not a good idea to try and repair a fill valve.

Worn Out Flapper Not Sealing

Another cause for a noisy toilet is a worn out flapper that isn't sealing. If the flapper doesn't sit tightly against the outlet in the bottom of the tank, it allows water to leak out into the bowl, making the toilet noisy and running constantly. A worn flapper can be replaced by unsnapping the old one from the hinge assembly and connecting a new one. Silicone grease, dabbed around the inside of the flapper rim, will help keep a watertight seal.

Float Out of Adjustment

The float connected to the fill valve automatically cuts the water inlet on the valve when the water level in the tank reaches the fill level. A float that is out of adjustment won't close the fill valve and will keep the valve running. Older style ball floats can be adjusted by bending the float rod up or down to raise or lower the water level, while newer, doughnut style float valves are adjusted by turning the adjustment screw.

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About the Author

Nathan McGinty started writing in 1995. He has a Bachelor of Science in communications from the University of Texas at Austin and a Master of Arts in international journalism from City University, London. He has worked in the technology industry for more than 20 years, in positions ranging from tech support to marketing.