Toilet Leaking — gasket

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   From a dry position, watch the leak without wiping away its first trace. Follow the water path visually from the supply stop or hose, around the fill-valve shank and tank underside, across the tank-to-bowl seam, and around the bowl base.

   Expected result: The first wet point is the supply connection, fill-valve shank, tank-to-bowl joint, bowl base, wall/floor penetration, or cannot be seen because water is pooling or contaminated.

   Next step: If water is active and the stop turns normally, close it and keep the toilet unused. Record the location for a plumber instead of tightening or dismantling the joint.

   Stop if: Stop for sewage, rapid flow, overflowing water, water near electrical equipment, soft flooring, cracked porcelain, or a seized supply stop.

   Why this matters

   Why: A gasket or washer can only be considered after its joint is the first wet point. Water at the bowl base or concealed penetration is not evidence for replacing a tank gasket.

2. Check 2

   When the tank and floor are dry enough to observe safely, look at the tank-to-bowl seam and the underside of the tank while the toilet is refilling or after a normal flush. Do not place hands under the tank, tighten bolts, or rock the tank.

   Expected result: Water appears at the seam or around a tank outlet/bolt, appears only during refill, appears only after flushing, or remains dry while another area wets.

   Next step: Close the supply if safe and request plumbing service for a gasket or connection assessment. Do not keep flushing to reproduce the leak.

   Stop if: Stop for tank movement, porcelain cracks, fast flow, water under the fixture, or any need to hold or lift the tank.

   Why this matters

   Why: A seam leak during a flush/refill cycle supports a tank-to-bowl seal or connection issue; water at the fill-valve shank supports that valve's gasket; a dry seam moves the diagnosis elsewhere.

3. Check 3

   Observe the accessible fill-valve and supply joint without touching it. Note whether water is entering the tank continuously, spilling into the overflow tube, or appearing outside around the shank, locknut, hose, or shutoff.

   Expected result: The valve continues to admit water, the level reaches the overflow, the shank/hose wets, or the external joint stays dry.

   Next step: If the valve cannot shut off or the level approaches the overflow, close the supply and call a plumber. Do not adjust or replace a wet valve connection under pressure.

   Stop if: Stop for overflow, uncontrolled water, corrosion, a loose tank, cracked porcelain, or water near electrical equipment.

   Why this matters

   Why: Overflow is a fill-valve or float-level symptom, while water at the shank or hose is a joint seal/connection path. A fill valve that shuts off normally does not explain a separate tank-to-bowl or base leak.

4. Check 4

   If there is no active exterior leak, the bowl is clear, and the tank is stable, add a few drops of food coloring or a dye tablet to the tank without flushing. Wait 10 minutes and look for color in the bowl; flush afterward to avoid staining.

   Expected result: Color appears in the bowl during the wait, or the bowl remains clear while the exterior joints remain dry.

   Next step: Give the dye result to the plumber and do not replace a gasket solely because the toilet is running. Stop the test if the bowl cannot be flushed safely.

   Stop if: Do not perform this test with sewage, a blocked/overflowing bowl, uncontrolled water, or a tank that is unstable or cracked.

   Why this matters

   Why: Color in the bowl identifies a tank-to-bowl flapper or flush-valve seal leak, not a gasket at the supply or tank exterior. A clear bowl makes a silent flapper leak less likely and leaves the earlier wet-point evidence to interpret.

5. Check 5

   Inspect the bowl base and adjacent floor/wall from a dry standing position after the toilet has been used normally, without rocking the fixture or reaching behind it. Note whether the wetness starts at the base, follows the supply line, or appears from a wall or floor penetration.

   Expected result: Water forms at the bowl base after flushing, is present even when the toilet is not used, follows the supply route, or appears from a concealed area.

   Next step: Close the supply if safe, avoid flushing, protect the floor without touching contaminated water, and call a plumber for base, drain, or concealed-pipe diagnosis.

   Stop if: Stop for sewage, a moving bowl, cracked porcelain, soft flooring, ceiling staining below, or active water entering the wall/floor.

   Why this matters

   Why: A base leak can involve the bowl-to-drain seal or porcelain, while a leak between uses can indicate a supply or tank path. A concealed path needs building/plumbing assessment; changing a tank gasket will not test it safely.

6. Check 6

   Make a service record rather than disassembling the toilet: first wet point, leak timing, whether the supply stop controls it, tank level relative to the overflow, dye result, visible porcelain condition, and any recent tank, fill-valve, or supply work.

   Expected result: The record points to a fill-valve/shank gasket, tank-to-bowl seal, supply washer, bowl-base seal, overflow, flapper, or concealed plumbing path.

   Next step: Leave the supply closed or the toilet unused when practical until the plumber confirms the leak is controlled and the fixture is stable.

   Stop if: Stop all homeowner work if the source is unclear, the leak returns, or any repair would require disconnecting a pressurized hose, lifting the tank/bowl, or handling sewage.

   Why this matters

   Why: A location-and-timing record lets the plumber select the correct sealing repair and avoid replacing an unrelated gasket. A gasket that needs separation of pressurized or porcelain parts is a professional repair boundary.