Which of the following is NOT a reason for a float-controlled valve in a water closet flush tank to leak?

A float-controlled valve in a water closet flush tank is designed to regulate the water level within the tank, making sure it fills to an appropriate level for effective flushing. The factors typically causing leaks can be characterized by mechanical failures or adjustments.

Floating steady level, while it accurately describes a situation where the float is maintaining the water level, does not contribute to leakage. The float's primary function is to signal when to stop the water flow when the tank reaches the correct level. In contrast, improper float adjustment, valve washer wear, and foreign material obstruction all directly influence the valve's ability to seal properly, resulting in leaks.

Improper float adjustment may cause the tank to either overfill or not fill enough, leading to continual running water or inadequate flushing, but it does not inherently cause the valve to leak. Valve washer wear results in degradation over time, making it more difficult for the valve to create a watertight seal, thus leading to leakage. Finally, foreign material obstruction can prevent the valve from functioning properly, causing it to leak around the clean-out area or fail to close completely. Each of these situations leads directly to leakage, whereas maintaining a steady, properly adjusted float does not create these issues.