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Water Leaking From Top Of Toilet Tank

The most important part inside the tank is the flush valves "overflow pipe." The overflow pipe is the safety net for your toilet. When properly set it will prevent water from overflowing the tank and flooding into the home.

The four critical areas of a toilet tank are:

  1. The Tank Lever Hole
  2. The CL (Critical Level) Mark located on Fluidmaster's fill valve
  3. The Overflow Pipe (top end)
  4. The Water Level

The water level should be indicated by a mark or (depending of the age or use of the toilet) a water stain on the inside of the tank. When rebuilding a toilet it is very important to set the fill valve to achieve this height.

New flush valve "overflow pipes" are designed to be tall so that they can work with older or larger toilets as well as modern or smaller toilet tanks. In most cases the overflow should be cut to ensure the safety of the home. The overflow pipe should not extend over or be at the same height as the tank lever hole (the hole that a tank lever will go through). The tank lever, when installed, does not make a water tight joint or seal; it is for this reason the flush valve “overflow pipe” needs to be below the tank lever hole. In most cases the overflow pipe, once cut, should be below the tank lever hole by as much as 1 inch to ensure the safety of the home.

The CL Mark on the Fluidmaster fill valve has a mark located at the top of the fill valve just below the anti siphon holes (the small windows that encircle the valve shaft). This mark is the CL (Critical Level) Mark that is used to measure the valve for proper water height. Adjusting the fill valve so the height of this mark is 1 inch above the top of the flush valves “overflow pipe” will properly set the valves anti-siphon design and, in times of emergencies, will not let the tank water siphon or get sucked back into the main water supply. Setting the CL Mark properly ensures proper water level inside the tank, which will give you a strong or proper flush.