How do I get my toilet to stop hissing?

Why is my toilet making hissing noise?

A: The hissing noise is most likely a defective refill valve. There are two valves inside the tank on the back of the toilet bowl. One is the flapper valve, located at the bottom of the tank, which allows water to enter the bowl.

How do you fix a toilet pump noise?

Will a hissing toilet overflow?

The cause may be a defective fill valve, but more often it’s simply a misadjusted float. If the hissing isn’t accompanied by water spilling into the overflow tube, air may be making the hissing sound. In that case, the toilet doesn’t have a leak, but something is definitely wrong.