Toilet Hissing Very Loudly (with video)

Hey everyone!

our toilet in our master bath off the bedroom has always had a loud hissing noise after being flushed since moving in 3 years ago. However, it seems to be getting worse. It's so bad that if someone uses the restroom in the middle of the night that it wakes the other up. Even with the door closed it's extremely loud and seems to reverberate through the walls.

We also have some water lock / hammer lock happening that is kind of hard to hear as it's a big thunk and happens right as / before the hissing stops. For the hammer lock I tried turning off the main waiter and opening all of the faucets, tubs, draining the washer and dishwasher as well as flushing the toilets and then turning back on... it didn't do anything (unfortunately).

However, my main concern is the hissing noise. It's way too loud. I've looked online and it seems it could be one of approximately 10 things, and I'm not a toilet expert nor do I feel like taking every single thing apart one at a time. Was hoping this video may help someone cue in on what exactly might be causing this noise?

Any help would be very appreciated. Thank you so much.

(Video)

https://photos.app.goo.gl/ukBNVzNsVcaDVyNV8

sounds like excessive pressure
turn the valve under the toilet off half way and see if that helps

frodo said:

sounds like excessive pressure
turn the valve under the toilet off half way and see if that helps

Click to expand...

Thank you so much! That seems to have helped! Not sure about the hammer lock but the big issue was the hissing, which is now mostly gone. Appreciate it!

Did one of those 10 possible solutions suggest replacing the flush valve?
That may fix both of those problems, particularly since the "water hammer noise was associated with the toilet flushing.

Diehard said:

Did one of those 10 possible solutions suggest replacing the flush valve?
That may fix both of those problems, particularly since the "water hammer noise was associated with the toilet flushing.

Click to expand...

That may be something worth looking into, as we still have some water hammer. Also, the pipes themselves seem to be loud through the walls. The hiss in the bathroom has pretty much disappeared thanks to changing the pressure, but still loud (not as loud) in the bedroom as the pipe seems to still be quite noisy after a flush... any tips for that?

jblock22 said:

That may be something worth looking into, as we still have some water hammer. Also, the pipes themselves seem to be loud through the walls. The hiss in the bathroom has pretty much disappeared thanks to changing the pressure, but still loud (not as loud) in the bedroom as the pipe seems to still be quite noisy after a flush... any tips for that?

Click to expand...

When you say, "...but still loud (not as loud) in the bedroom as the pipe seems to still be quite noisy after a flush.", are you referring to the hissing sound or the water hammer sound?

Flush valve are usually under $20. I strongly suggest you put one in. The are quite easy to do.
Very common for flush valves to make strange noises when they get worn out. And the fact that the water hammer sound, "happens right as / before the hissing stops." is a good indication that it's the flush valve causing it. Could be something loose in there shuts quickly, which is the cause of water hammer.
Reducing the pressure is a good temporary solution but not the problem.

You can also buy small hammer arrestors, which are designed to go after the sill clock. Sioux Chief makes them, and you can buy them on amazon if you have trouble buying them local.