What type of expansion tanks requires shutoff valves to be installed at connections?

Expansion tanks are crucial components in plumbing systems to accommodate the thermal expansion of water as it heats up. The installation requirements for these tanks can vary depending on their design.

Nondiagram-type expansion tanks, which operate without a flexible membrane, typically need shutoff valves at their connections. This is necessary to maintain the system's pressure and allow for maintenance or replacement without draining the entire system. The shutoff valves enable isolation of the expansion tank, which can facilitate service work or replacement while keeping the rest of the water supply functional.

In contrast, diaphragm-type and bladder-type expansion tanks have built-in membranes that separate the air charge from the water. These designs manage expansion and pressure changes internally, making shutoff valves less critical. Therefore, the requirement for shutoff valves is most pertinent to nondiagram-type tanks due to their construction and function within a plumbing system.