Causes and Effects of Leaking Toilet:  Stuck/Open-Flapper: Caused by a bound up chain connecting the toilet’s flush handle to the flapper or by. the flush handle getting stuck in the down position. Water loss translates to 4,800 gallons/day or 200. gallons/hour.  Warn/Warped Flapper (silent leak): Caused by normal wear and mineral buildup on flapper over time. Such wear is contributed to by an increasing level of chemicals added to municipal water systems to purify. the water.