(Replacement caps are no longer available at Home Depot and I've included updated links where they can be purchased) I'm a Calgary realtor (https://www.mikolajow.com) and often come across simple fixes to common household DIY problems. When a friend asked for help with their "hissing" running and leaking Toto toilet - we found it was dripping into the bowl and wasting a substantial amount of water. We were able to quickly and easily install an all-new replacement flush valve mechanism - a relatively easy task, which cost about $25 at Home Depot Canada.

Well, Murphy's Law decided to remind me of its existence and within a few days, my Toto toilet began making the same hissing noise! Curiosity got the best of me and, while tinkering, I noticed the rubber valve under the top cap had deteriorated and started to curl - from chlorine and hard water mineral deposits. Back at Home Depot, I discovered the top cap & valve was available for $5 and, this time, an entire flush valve replacement wasn't needed.

In the USA, the easiest way to buy appears to be ordering from Amazon https://www.amazon.com/Korky-Replacem... but it seems to be available at True Value and Ace Hardware.

In CANADA, The Korky Quietfill Replacement Cap is $6.59 at Rona https://www.rona.ca/en/product/korky-... or Lowes https://www.lowes.ca/product/toilet-f... and is a replacement for Toto, Korky Quietfill and Platinum fill valves. There's a two pack of caps for about $20 at Amazon.CA as well. https://www.amazon.ca/Korky-Toilet-Re...

I've been a Calgary Realtor for over 25 years - now brokered by eXp Realty.