American Standard Piston Assembly for Manual Toilet Flush Valve 1.0 GPF(Blister Pack 100) - AMS-M964905C-007

It's the internal piston assembly, the working guts of a manual (handle-operated) toilet flush valve. When the handle is pushed, the piston lifts off its seat and releases the metered charge of water, then reseats to shut the flush off. It's the part you replace when a flushometer runs on, flushes short, or won't shut off, rather than swapping the whole valve body. American Standard supplies it under part number M964905C-0071000A.

No. This piston is built for 1.0 GPF manual toilet flush valves, and the piston is what meters the flush volume. Putting it in a 1.6 or 1.28 GPF valve changes the water delivered per flush and can put the fixture out of spec. Match the piston to the GPF stamped on the valve you're repairing.

It's specified for manual flush valves, the handle-operated kind. Battery or hardwired sensor flushometers use a solenoid-driven operating kit instead, so a manual piston isn't the repair part for those. Check whether the valve has a handle before ordering.

It ships as a blister pack of 100 pistons. That's a bulk maintenance quantity aimed at facilities standardized on American Standard 1.0 GPF manual flushometers, a school, hospital, stadium or multi-family portfolio doing a rebuild campaign across a lot of fixtures. If you're fixing one restroom, this is more piston than the job needs.

A flushometer that runs on is usually the piston not reseating, from a worn seal or grit under the seat. On a manual 1.0 GPF American Standard valve, this piston assembly is the rebuild part for that symptom. Shut the control stop, pull the cover and the old piston, flush the line briefly to clear debris, and drop the new one in. If the valve still runs after that, look at the control stop or the handle assembly.