This sound can happen intermittently and occur every few minutes or every few hours. Such a refill sound is usually alerting you that your toilet is losing water, either internally (if there's no water on the floor or exterior of toilet) or externally leaking if you see water outside the toilet.
CAUSE & SOLUTION
If your toilet is making noise when not in use, a worn or faulty flapper is likely the reason. If the flapper is not working properly, it can cause your toilet to constantly run, make noise, and ultimately, increase your water bill. Replace the flapper.
A toilet that cuts on and off by itself, or runs intermittently, has a problem that plumbers call a "phantom flush." The cause is a very slow leak from the tank into the bowl. This problem is almost certainly caused by a bad flapper or flapper seat.
In most cases, a dirty or bad toilet fill valve seal is the cause of a squealing or whistling toilet.
Most commonly, something is preventing the flapper from closing completely. Therefore, it is always letting a small amount of water out of the bowl. Then, once the toilet tank is empty, the fill valve is triggered, and it refills the tank. That's what you hear when your toilet runs for a few seconds—the tank refilling.
Ghost flushing wastes water, which can result in higher water bills. Even a small leak can waste significant amounts of water over time, so it's essential to find and repair the leak quickly.
Check Your Refill Tube
If the refill tube is inserted too far into the overflow pipe, you should pull it out and attach it to the outside overflow pipe. This is done to keep the tube from entering the overflow pipe and usually will stop an internal leak from the tank to the bowl that caused the ghost flushing.
A hissing sound can mean that the refill valve is still letting a tiny bit of water into the tank because it hasn't shut off like it's designed to. The valve shuts off automatically based on the water level in the tank. A faulty valve or one not set properly will keep running.
The term ghost flushing is used to describe a common plumbing issue where the toilet seems to be flushing every few minutes even when no one is using it. This can be a frustrating problem for homeowners or businesses to deal with since it can cause a rise in utility costs.
Ghost flushing happens, yes, for real, when the toilet tank is leaking, the water level drops until it refills. Out of nowhere, you hear the sound of water running back into the tank. It sounds like a flush.
Toilet and faucet leaks The most common cause for a high-water bill is running water from your toilet. A continuously running toilet can waste up to 200 gallons a day or more depending on the volume flow down the drain.
A worn or faulty flapper could be the reason why your toilet is making noise when not in use. If the flapper is not working properly, it can cause your toilet to constantly run and even waste several gallons of water. Fixing a bad flapper is not a tough job though.
These ballcock valves come with an armature and ball that begin to vibrate when the toilet tank refills after flushing. This vibration of valves causes the whistling sound that you hear. The valves vibrate due to a damaged fill valve gasket, or it could also be due to simple wear and tear that has worn down the valve.
To answer your question in the simplest way, the whistling sound is usually caused by a faulty fill valve. Age and usage often cause this piece to deteriorate, hence the sound. Let us get into more detail about what a fill valve is, how it works, and how it can cause your toilet to whistle.
Don't put off repairing a whistling toilet.
It's really important that you don't ignore the whistling, and you look at it as soon as you notice it. The whistling could go on for a long time, or the valve could completely fail very quickly.
The phenomenon is referred to as ghost flushing. It is when your toilet flushes all by itself, but it isn't caused by any paranormal activity. Ghost flushing happens because water is slowly leaking out of the tank and into the bowl.
Droplets produced by flushing toilets were found to harbor both bacteria and viruses which had been seeded. The detection of bacteria and viruses falling out onto surfaces in bathrooms after flushing indicated that they remain airborne long enough to settle on surface throughout the bathroom.
It is usually caused by a blockage somewhere along with your sewer system. That could be a blockage in the vent stack, a clog inside the toilet, a blocked drain- or the sewer drain itself may have broken and collapsed. Some of these causes are easier to fix than others.
Toilet Parts
The toilet's flush valve will typically last 6-7 years. A toilet fill valve might only last four to five years. In general, you should expect to replace the parts in your toilet every so often while keeping the actual bowl in place.