Most instructions I've found online and in books say that a toilet fill valve will have a Critical Level marker on it indicating that the top of the overflow tube should be 1" below it. In one of my toilets I have a fill valve which is entirely submerged in the water, thus definitely not 1" above the outflow tube. Is it possible that this is a correct installation or are there no exceptions to this rule? There is a "Hoov-R-Line" brand name on the device but I can't find any documentation online.

Toilet tank

  • It shouldn't be completely submerged; there should be an air gap to ensure against backflow.
    – keshlam
    Aug 16, 2016 at 23:40
  • Thanks, replaced the fill valve with an adjustable one and set it to the correct height.
    – MarcGuay
    Aug 17, 2016 at 20:23


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