Identifying and Rebuilding Nelson 9001/9002 Sprinkler Valves

Mystery Valves in New Home's Irrigation System

A homeowner with a Nelson 8300 controller found four unmarked black valves in the valve box. One zone runs continuously unless the controller is unplugged, and another has low pressure. The goal: rebuild all four valves with original parts.

Valve Identification

The valves are Nelson model 9001 or 9002. Both share the same diaphragm and solenoid; the difference is pipe connection (glue-in vs. threaded). Look for markings on the top or sides of the valve body.

Rebuild Procedure

1. Shut off water to the system.
2. Remove the six screws holding the valve bonnet to the body.
3. Extract the diaphragm from between the halves.
4. Disconnect solenoid wires, labeling them for reconnection.
5. Take the bonnet (with solenoid) and diaphragm to an irrigation supply store for exact matching parts.

Pro Tip

Since zones function except for the two issues, rebuilding all valves proactively prevents future failures. The constant-on zone likely has a stuck solenoid plunger or debris preventing diaphragm seating. Low pressure may indicate a torn diaphragm or clogged solenoid port.