Many questions here ask about how to fix a toilet that continues to run.

How do you PREVENT a running toilet from happening? Alternately, do mechanisms exist that stop it from running for more than some maximum time or volume, as a fallback?

  • 2
    Take away it shoes
    – Kris
    Mar 23, 2019 at 1:01
  • You may want to amplify this with what you've looked for, why it's a problem, and a better view of your overall goal, and what level of resources you are willing to throw at it. E.g. A microphone with a bandpass filter that 'listened' for running water, tied into a timer and an electric valve. Set the timer to longer than normal fill time. If sound was longer than that, activate the shutoff valve. Mar 23, 2019 at 1:23
  • 4
    you prevent a running toilet from happening by ensuring that all the components in the tank are in good working condition
    – jsotola
    Mar 23, 2019 at 2:40
  • Tie it up on steel chains. Mar 23, 2019 at 2:55

2 Answers 2


I'm not aware of any device on the market but I could imagine a solenoid valve with us 555 timer chip connected to a water level sensor where it would reach minimum and then start the timer for a minute or so, enough time to fill it. That would do the trick. It could be made battery operated. I wouldn't know how to describe how to build it. It's more electronics than DIY. Setting up the flapper properly is an art form, especially when retrofitting one.

  • This is an answer to the question IMHO, but does not answer how to refill the toilet when a problem occurs.
    – davidgo
    Mar 24, 2019 at 5:39

Presumably it is running because it is not staying full (leaking thru flapper) or float is not working (in which case tank would overflow). If it is not overflowing then it is the flapper. That has always been the case for me. Overflowing is pretty obvious. That has only happened once, thank goodness because it was expensive.

Flapper rubber oxidizes and gets hard and the seal is weak. You could test to see if it the flapper by putting a brick on the flapper. That should improve the seal. See if the toilet stops running. If so, get a new flapper. Bring your old flapper to the hardware store and try to get a match. They are not hard to install.

One might think (read: I thought) that vaseline on the bottom of a poorly sealing old flapper would help it seal. In case you too have that thought: it does not.

  • Any ideas on how to make a flapper last longer? It seems that the manufacturers could do a lot better. Mine aren't lasting much more than a year. Mar 30, 2019 at 13:43
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    Interesting question. I think the problem is chlorine in the water that oxidizes the rubber. I wonder if you had a bunch of other rubber stuff in the tank if that stuff would soak up the chlorine so there was less available to oxidize the flapper. You could test it - get a bunch of rubber surgical tubing and wrap it around a brick or something that will stay put. See if your flapper lasts longer with the rubber tubing running interference for it. That rubber should be even more vulnerable to oxidation than the silicone rubber flappers are made of.
    – Willk
    Apr 10, 2019 at 3:02
  • Willk, brilliant! Your comment would be a great potential answer. Apr 11, 2019 at 17:51

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