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  • Writer's pictureJolly Plumbing

Why is My Toilet Making a Hissing Noise?

Updated: Nov 8, 2022

Are you wondering why your toilet is making a hissing sound?

Here's how you know you can easily solve the problem, if you immediately take the lid off the top, the hissing sound will stop. The hissing sound means that the refill valve allows a small amount of water into the tank, preventing it from shutting off as intended. If this does not solve the problem, read on for more troubleshooting options.

Whether it’s loud or fairly quiet, a hissing toilet can be an annoying sound for any homeowner to deal with. The good news is that a hissing noise is a fairly common issue, especially if your toilet is older, and can often be fixed with a handful of tools and a couple of inexpensive parts. The hissing comes from an issue with the flush valve assembly, which is allowing water to leak from the tank into the toilet bowl.

Check the Refill Valve When You Hear the Hissing

Every time you flush your toilet, clean water from the tank empties into the bowl and is then refilled by your home’s water supply. The valve responsible for making sure the water is at the right level is the fill valve. The fill valve can be blocked by a buildup of sediment, be incorrectly calibrated, or it may have broken down over time which causes the tank to over-fill. Where the hissing sound may be coming from is the excess water flowing into the overflow pipe. Recalibrating or replacing the valves is a pretty easy repair to accomplish.

There are two main types of fill valves, one looks like a plastic ball that sits on top of the water and the second is referred to as a ball-cock which looks like a small inflated balloon attached to a rod. Each of these two fill valves keeps the water in check, but most newer toilets will employ the plastic ball/bouy design. To adjust the water level, simply find where the float is connected to the rest of the system, which usually looks like a pair of plastic clips or screws. Then adjust the float so it sits below the overflow pipe, which should solve the issue.

Check the Flap Valve If the Hissing Continues

If you attempted the repair above with the fill valve and it still didn’t fix the issue, then your problem may lie deeper into the tank with the flap valve. The flap valve is usually gray, black, or blue rubber or hard plastic and its job is to lift up and allow for water to rush into the bowl whenever the toilet is flushed. Over the years, the seal located on the underside of the flap valve that keeps the water in check when the toilet is not in use can become brittle or covered in sediment buildup. Whenever small amounts of water are leaking into the toilet bowl, it can cause a loud hissing noise.

Occasionally just cleaning the flap valve and seal is enough to solve the problem. You can do this by shutting off the water supply and unscrewing the flap valve from the bottom of the tank. Inspect the seal and clean it will mild dish soap and a sponge. If the valve seal looks cracked or compromised in any way, then it will need to be replaced. Take the seal with you when you go to the home improvement store to ensure that you are buying the correct one.

If neither of these repairs were helpful, or you simply want a second opinion from an experienced plumber near you, give our team at Jolly Plumbing a call today!

Check Out What People Are Saying About Our Toilet Repair Services:

Here’s what Steven Mizak had to say about us on Google:

“Had to have a pressure reduction valve replaced so I called Jolly. Daniel showed up the same day and not only replaced the valve but helped me install a thermal expansion tank as well. He was great and happy to explain all the aspects of the job to help me learn. I highly recommend Jolly plumbing!”

Rating: 5/5 ⭐⭐⭐⭐⭐

Date: 11/7/2020

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Nov 24, 2020

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