Drain Running — seal, tank

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

1. Check 1

   Locate the sound and visible water without touching contaminated water: check whether the flow is inside one toilet tank and bowl, at an exposed supply connection, at a floor or cleanout, or from a buried or outdoor drain path.

   Expected result: Only one toilet makes a refill sound or shows water entering its bowl, or water is instead appearing at a pipe, cleanout, floor drain, yard, or more than one fixture.

   Next step: For a toilet-only pattern, continue with the tank checks. For any external, sewage, buried-line, or multi-fixture pattern, reduce water use, keep away from contaminated water, and call a licensed plumber.

   Why this matters

   Why: A one-toilet refill pattern fits a tank seal or fill-control problem. A pipe, cleanout, sewage, or multi-fixture pattern is not established as a tank-seal issue.

2. Check 2

   If the bowl is rising or the toilet cannot stop filling, turn the local toilet water valve clockwise only until flow stops if it moves normally; do not force a seized valve. Keep the floor dry and do not use the toilet until the cause is identified.

   Expected result: The valve stops the refill and the tank remains stable, or the valve will not turn, the connection leaks, or water continues despite the valve being closed.

   Next step: If the valve cannot safely stop water, close the home's main water shutoff only if it is safely accessible and arrange a plumber. Do not use tools to force a valve or reach through sewage.

   Why this matters

   Why: A working local shutoff can limit water damage while a toilet issue is investigated. A seized valve, leaking connection, or uncontrolled flow needs professional attention rather than force.

3. Check 3

   With the water supply controlled and the tank area dry, lift the tank lid and observe the water level, the overflow tube, the flush-valve seal or flapper, and the chain or handle linkage without pulling parts apart.

   Expected result: Water is visibly flowing over the overflow tube, the flapper is not seated, the chain is tangled or too tight, the handle is held down, or the tank water is quiet but a refill sound returns periodically.

   Next step: Correct only a plainly loose or tangled external linkage if it moves freely and the exact toilet instructions allow it. Do not bend an unknown float or dismantle the flush valve; continue with the dye test or call a plumber if the cause is unclear.

   Why this matters

   Why: Overflow points toward fill-valve, float, or water-level control. A seal that does not seat or a chain that holds it open points toward the tank seal or linkage. Periodic refilling with no visible overflow is consistent with a quiet seal leak.

4. Check 4

   For a quiet or periodic leak, place a few drops of food coloring or a dye tablet in the toilet tank and wait without flushing, following the EPA WaterSense test interval; then inspect the bowl for color and flush afterward.

   Expected result: Color appears in the bowl, or no color appears while the tank still overflows or the fixture continues refilling.

   Next step: If color appears, turn off the local supply and have the correct seal or flapper replaced according to the toilet's model information. If there is no color but overflow continues, have a plumber inspect the fill control and overflow setting. Flush after the test to avoid staining.

   Why this matters

   Why: Color in the bowl confirms water is crossing the tank seal or flush valve. No color makes a tank-to-bowl seal leak less likely and shifts attention toward the fill valve, overflow level, handle, or another water source.

5. Check 5

   Compare the old seal or flush-valve assembly with the toilet model information only after the water is off and the tank is empty enough for safe work; check for a deteriorated seal, mineral buildup, damaged seat, or a chain that prevents closure without scraping or forcing the valve.

   Expected result: The seal is cracked, hardened, warped, mineral-coated, or the seat is damaged; alternatively the seal looks intact but the fill valve or overflow remains the source of flow.

   Next step: Use the toilet model and the old part to identify a compatible seal, or have a plumber replace the seal, seat, flush valve, or fill valve. Do not rely on an unverified universal part or alter the water level beyond the manufacturer's guidance.

   Why this matters

   Why: A worn seal can cause continuous or silent leakage, but not every running toilet uses the same flapper or flush-valve design. A failed fill control requires a different part and adjustment.

6. Check 6

   After one model-appropriate seal or linkage correction, observe one refill and verify that the bowl is not receiving a continuous stream and that no water is escaping onto the floor or into a hidden drain path.

   Expected result: The refill stops normally and the bowl remains quiet, or the toilet continues running, leaks at the tank or supply connection, backs up, or the original sound came from outside the toilet.

   Next step: For continued or external symptoms, leave the local water supply off when safe and call a licensed plumber. Request inspection of the toilet, branch drain, building drain, or sewer connection as the observations require.

   Why this matters

   Why: A stable post-repair refill supports a resolved tank-seal or linkage problem. Continued running, external leakage, backup, or a different source means the first diagnosis was incomplete or another plumbing defect is present.