Why does a toilet tank refill every few minutes even when no one flushes it?

If a toilet tank refills every few minutes without being flushed, it is usually a sign of hidden water leakage inside the tank. The refill only happens when the fill valve starts working. When water slowly leaks from the tank, the water level drops. After a short time, the fill valve detects the lower water level and starts refilling the tank again.

In many cases, this problem is related to the flush valve seal, flapper, or other sealing parts inside the tank. If the seal is aged, deformed, or not closing properly, water may slowly leak into the toilet bowl even when the toilet is not being used.

This intermittent refilling is a useful warning signal. By observing whether the tank refills repeatedly, you can identify possible leakage from the flush valve or other tank components early, before it causes higher water bills or more serious toilet repair problems.