How to Troubleshoot a Fluidmaster Fill Valve

Updated February 21, 2017

A Fluidmaster self contained float and fill assembly unit is the modern version of the old toilet fill tube, with separate float and ball assembly. Fluidmaster has combined the fill and float portions inside of your toilet tank to create a one piece unit. This results in fewer parts that can go bad, and an easier to service unit to troubleshoot if a problem occurs. Essentially, by using standard Fluidmaster replacement parts, a Fluidmaster unit will last the lifetime of your toilet.

Check the black vinyl refill tube that attaches to the Fluidmaster unit near the top. If it is hanging loosely into the overflow pipe, it may act as a siphon and drain water from the tank back down into the valve. Either clip the included angle adaptor onto the overflow pipe at the top, or if no angle adaptor is available, one can be purchased at any local hardware store.

Adjust the water level clip on the side of the Fluidmaster for a higher water level. This is a metal slip ring attached to a control arm on the tank side of the unit. It can easily be slid up or down to get the correct toilet tank water level as desired, but there may be a bit of trial and error when sliding the clip to obtain the correct level.

Water levels that can not be raised by doing either one or the other of the previous steps will mean that the toilet flapper is leaking, and will need to be replaced before any other Fluidmaster adjustments can be made.

Turn off the main water feed to the Fluidmaster by turning the feeder valve in a clockwise direction. The feeder valve will be located beneath the toilet connected to a pipe coming from the wall.

Remove the cover of the Fluidmaster. The cover is located on top of the unit, and can be turned an 1/8 of a turn in a counterclockwise direction for removal. Pull off the cover, place an inverted cup over the top and hold it firmly in place, then turn the water feeder valve back on. Allow the water to flush out any debris that may be clogging the unit. Turn the feeder valve back off, replace the cover and turn the valve back on.

Replace the inner rubber seal if water flow problems persist after flushing. Get a Fluidmaster No. 242 Replacement Seal from any hardware store. Turn off the feeder valve and remove the Fluidmaster cover. Carefully grasp and pull out the old seal inside, and replace it with the new seal. Press it into place, put the cover back on and turn the feeder on.


When checking the seal on a Fluidmaster, if any calcium or lime deposits are noticed, a piece of wire or coat hanger can be used to scrape them away, or a stiff hobby brush can also be used as well.

Things You'll Need

  • Fluidmaster toilet tank unit
  • Fluidmaster No. 242 Replacement Seal
  • Angle adaptor
  • Scissors
  • Cup
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About the Author

Dale Yalanovsky has been writing professionally since 1978. He has been published in "Woman's Day," "New Home Journal" and on many do-it-yourself websites. He specializes in do-it-yourself projects, household and auto maintenance and property management. Yalanovsky also writes a bimonthly column that provides home improvement advice.