A waxless toilet seal leaked into a kitchen ceiling for a year. What the install sheet says about flange height

The owner described the case on Reddit's r/Plumbing: a plumber opened the ceiling, found mold in the floor framing, and the leak stopped after a standard wax ring went in. Without the flange measurements, the cause of that leak cannot be pinned down from the description alone. The manufacturer's install sheet shows where the setup can go wrong.

Fluidmaster's 7530 instructions start with measuring the flange. If it sits above the floor, the spacer is discarded and the rubber seal goes on alone. If it is flush or up to 1/4 inch below, the spacer goes on foam side down with the seal on top, and the sheet warns that leaks may occur if the foam faces the wrong way. Deeper than 1/4 inch calls for the spacer plus two seals, and a flange more than 3/4 inch down needs an extender. The installer presses down on the bowl and tightens the nuts alternately, without overtightening, then flushes and checks for leaks.

If the bowl rocks, Fluidmaster's product page says to shim it when the gap is 3/16 inch or less and to build up the floor with a base plate when it is 1/4 inch or more. The International Residential Code, in Section P2705.1, requires floor-mounted fixtures to be secured to the drain connection and the floor with corrosion-resistant fasteners, and the contact area with the floor to be watertight.

For the damage below, EPA guidance says to fix the leak first and dry wet materials within 24 to 48 hours. A moldy area under about 10 square feet is usually a job the homeowner can handle; larger growth or heavy water damage falls under EPA's remediation guide for bigger buildings. Ceiling tiles and other porous materials may have to be thrown out, and EPA says not to paint or caulk over mold.