Flushometers error codes, explained
Sloan Royal/Regal-class commercial flush valves (Zurn similar). Codes below: Rebuild and sensor guides. Each guide covers what the code means, what you can safely try yourself, when to stop and call a technician, and what the repair typically costs.
Commercial toilet keeps flushing / won't shut off (Sloan-type flushometer)
Per Sloan's own troubleshooting documentation, a flushometer that runs continuously has a diaphragm problem: the bypass hole in the diaphragm assembly is clogged with debris (wash it under running water) or the diaphragm/relief valve is worn — replace the kit. The first response is always the control stop: the shutoff under the chrome cap beside the valve (flathead slot or vandal-resistant key) — turn clockwise to stop the water and end the flood while you sort out parts.
Weak flush, or the toilet flushes by itself (sensor flushometers)
Two documented Sloan facts: a weak or short flush usually means the WRONG diaphragm kit is installed — kits are matched to flush volume (GPF), and a low-consumption kit in a conventional fixture starves the flush — or supply pressure is low (Sloan flags below ~25 psi). And ghost flushing on sensor models is a RANGE problem, not a haunting: the sensor is set too far out and detecting the stall door or reflections; Sloan documents adjusting range via the override button. Dying batteries cause failure-to-flush, not phantom flushes — the low-battery signature is the red LED flashing 4 times when someone steps in range.
The $25 part that rebuilds a commercial toilet valve
Flushometers don't get replaced — they get rebuilt, and the diaphragm kit is the rebuild. Kits are matched by fixture type and flush volume: closet (toilet) kits in 1.28, 1.6, and 3.5 GPF; urinal kits in 0.5, 1.0, 1.5 GPF. The GPF is printed on the valve label or fixture. Sloan documents the mismatch failure explicitly: wrong kit = short, weak flush (or a water-waster in the other direction). Kits run $15–55 retail.