Dry the toilet and floor, then watch where water first appears and whether it occurs while the toilet is idle or flushing. Check the supply connection and cistern, use a dye test for an internal leak, then observe one controlled flush only if the pan base is dry.
Check in a safe order
Find the first wet point. Dry accessible surfaces and place paper towel near visible joints. Check whether water is tracking down from the cistern, wall or pipework above. If water at the pan base could be wastewater, do not touch it or flush again.
Inspect the toilet while idle. With the cistern full, look for moisture around the stop tap, flexible supply hose, inlet connection, cistern underside and external joints. Trace moisture upwards because water can travel along surfaces. Do not tighten, bend or disturb fittings.
Check the cistern water level. If the lid is safely accessible, lift it carefully and place it flat on a stable surface. Without touching the mechanism, check whether water is entering the overflow. This generally indicates a water-level control or inlet-valve problem.
Use a dye test. Add a small amount of food colouring to the cistern and wait at least 10 minutes without flushing. Colour appearing in the bowl confirms an internal cistern-to-bowl leak. It does not identify the failed component. Follow the toilet manufacturer’s instructions where available.
Observe one flush if the base remains dry. Watch the visible flush-pipe joints, cistern-to-pan coupling and pan base. Some toilets have a visible flush pipe; close-coupled models do not. Stop immediately if water emerges at the base.
Evenly spread droplets on a cold cistern may be condensation. Consider this only after excluding wet joints, spills and water tracking from above.
What the observations indicate
| Observation | Likely leak area |
|---|---|
| Stop tap, hose or inlet becomes wet while idle | Clean-water supply connection |
| Dye reaches the bowl while water remains below the overflow | Internal outlet valve or sealing path |
| Water enters the overflow | Inlet valve, float or water-level control |
| Water appears below the cistern only during flushing | Flush-pipe joint or cistern-to-pan coupling |
| Water emerges at the pan base during or after flushing | Possible pan connector or drain-seal leak; treat the water as contaminated |
| Even surface droplets without a wet joint | Possible condensation |
When to stop
Limit checks to observation, dye testing and safe isolation. Do not dismantle fittings, move the pan or remove the cistern.
For an active leak from the toilet’s water supply, close the stop tap only if it is accessible and turns easily. Never force a stiff valve or handle a damaged or actively leaking pressurised hose.
Stop using the toilet if wastewater appears at the base, the porcelain is cracked, the supply hose is damaged, or the source is concealed or inaccessible. Avoid contact with wastewater and keep others away from the area.
These faults require professional investigation rather than further homeowner testing. Contact our licensed leaking-toilet repair team for a leaking supply hose, wastewater at the base or an inaccessible source.