Your water pipes may whistle and sing after you flush the toilet, or they may bump and grind. Either way, something's wrong -- they shouldn't make any noise at all. When the pipes make loud banging sounds, the fault is in the pipes, but whistling sounds usually come from the toilet fill valve.
Whistle and Sing
Musical sounds from the toilet, such as whistling, humming and singing, usually originate in the fill valve, and they signify an older, metal ballcock mechanism that may need to be replaced. This type of fill valve is regulated by a plastic ball float on the end of an armature; as the ball falls into the empty tank, it opens the valve, and as the water level rises -- and the float with it -- the valve gradually closes. The whistling starts when the valve is almost closed, and it's usually the result of worn washers. Correct this in one of two ways:
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- Unscrew the screws holding the plate on the top of the valve and remove the plate. Lift out the armature and replace the washers on the end, then reassemble the valve.
- Replace the fill valve.
Replacing the valve is the more reliable of the two options because modern valves are plastic and won't whistle, even when worn out.
Bump and Grind
Loud bumping and banging sounds from the pipes when the toilet is filling are usually the result of water hammer -- an unwelcome byproduct of confining pressurized water in metal pipes. When the toilet fill valve opens, pressurized water repeatedly slams against the valve opening, which creates the banging sounds. Alternatively, you may hear a banging only after the valve shuts off.
Remedies for Water Hammer
You may be able to control water hammer at the toilet by partially closing the water supply valve to reduce pressure on the valve. You may also be able to stop the banging by securing loose pipes to the framing with pipe clamps. If neither works, you'll probably need to install a water hammer arrestor to correct the problem. An arrestor is an air-filled tube with roughly the same diameter as the pipes. Inside the tube, a piston separates the air-filled chamber from the water and absorbs excess pressure by compressing the air. Install the water hammer arrestor in the water supply pipe by cutting into the pipe and soldering it on in the same way you would install a coupling.