Storage tank screens can become clogged, usually with ________.

• A. Ice
• B. Sand
• C. Rust
• D. Algae

Answer: (A)

Screens in potable water storage tanks tend to clog from biological growth rather than inorganic debris. Algae readily grow in stored water when there’s light exposure and available nutrients, attaching to screen surfaces and forming mats that impede flow and increase headloss. This makes algae the most common culprit for screen blockage in storage tanks. Ice would only occur if water freezes around the screen, which isn’t the typical operating condition for a healthy distribution system. Sediment like sand or corrosion products like rust can contribute to clogging in some situations, but algae is the usual and most expected cause in a properly managed storage tank. Regular tank cleaning, keeping tanks dark to limit photosynthesis, and maintaining disinfectant residuals help prevent algae buildup on screens.