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This symptom \ issue appears (seemingly) randomly, so I have labeled it an intermittent failure. The float (of a 2 year old Fluidmaster toilet fill valve) intermittently fails to float and does not cut off the water. The resulting symptoms include

  • water is not shutoff and requires intervention
  • cylindrical black float is submerge beneath the waterline (photo below)

The patch has been to manually tap the float once and it will rise and shutoff the water. It would be nice if the root cause of a intermittent stuck-float were corrected.

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Although I could install a new fill valve, my concern is that I will arrive with the same problem in a few months. I would like to understand why this is happening so that the corrective action can be judiciously selected.

If you have experienced this problem please state this in your reply, as experience is preferred. Bonus if you have the experience and successfully corrected the problem.

1) Is this a a) design problem or b) maintenance issue?
2) if a), what was the replacement used?
3) if b) what corrective action was taken

Any lessons-learned or pitfalls to avoid are appreciated. Thank you

  • Root Cause - poor design - works when new, ages poorly.
    – Ecnerwal
    Jun 23 '17 at 22:43
  • @Ecnerwal did you end up using a different design (model)?
    – gatorback
    Jun 24 '17 at 1:05

I have had these same valves get to the point where they quit working reliably so yours may be on it's way. However I would venture to guess that one of the following could contribute to intermittent failure.

  1. The float on your particular valve may have been deformed slightly in its manufacturing process to that it is just a little out of ideal shape. This lead to the thing binding on the riser post if it was in just the right position.
  2. There may be some molding seam flash on either the float or the post that leads to a binding problem with the float when it rises with the water fill.
  3. Check to see if there is any possibility of mineral deposit build up in the working slide area of the float. This could lead to sticking or binding.
  4. Make sure that the float is fully away from the sides of the tank so that it never has the opportunity to scrape on the tank side.
  5. Check the upper valve lever arm hinge under the upper cover (turn water off before removing) and make sure it has nothing that could cause it to want to stay in the down position making to force the float to stay down.


These valves are really pretty inexpensive and it only takes about 30 minutes to replace one [provided your shut off valve is functional :^) ] so I recommend that you just get a new one and swap out the intermittent one.

  • I agree with all of the above, with one additional comment: I have experienced where the rubber diaphragm (if you turn off the supply water and carefully twist the top assembly CCW 1/4 turn, while holding the valve body to keep it from turning, it will come off- revealing the diaphragm) gets soft from age and "grips" on the actuating pin, preventing the float and pivot arm from moving. replace the diaphragm for $3. Jun 23 '17 at 20:40
  • Amazon price for a whole new unit is <$8.
    – Michael Karas
    Jun 23 '17 at 20:43
  • Yes I agree replacing the unit is what I might do, but then you have stop-valve, supply line, valve adjustment, and tank seal issues to deal with. Jun 23 '17 at 20:47
  • @MichaelKaras Good call: I found & installed a Fluidmaster Pro45. Maybe the follow-on question (for another thread), is which fill-valve is reliable given that this one failed within 2 years.
    – gatorback
    Jun 24 '17 at 0:53
  • What has been the experience with the Korky fill valves? Jun 24 '17 at 3:24

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