Which of the following is NOT a type of water storage facility?

Steam boilers are primarily used for heating purposes and do not function as water storage facilities within water distribution systems. Their primary role is to generate steam for heating or power generation, utilizing water as a medium but not serving the purpose of storage in the context of water distribution.

In contrast, elevated tanks, clear wells, and hydro pneumatic tanks all serve specific functions related to water storage and distribution. Elevated tanks are designed to store water at a height to provide necessary pressure for distribution systems. Clear wells provide storage for treated water to ensure a reliable supply and help with sedimentation or settling. Hydro pneumatic tanks are used to maintain pressure in a water distribution system and hold a certain volume of water, but their main purpose is controlling pressure rather than long-term storage. Thus, identifying steam boilers as not fitting into the category of water storage facilities is accurate.