The Tecmark 1-5 PSI 1/8" NPT Pressure Switch, part 3903-BP, is a reliable safety-related component used in spa and hot tub control systems. It monitors water pressure in the heater or plumbing system and sends an electrical signal when the correct pressure (flow) is present, helping the control board manage heater operation safely.

Specifications:

• Brand: Tecmark Corporation
• Also sold under part numbers 5-20-0008, TDI3903BP
• 1-5 PSI set point — factory-set at approximately 1.5 PSI, not adjustable
• 1/8" NPT connection — standard male pipe thread
• SPST (single pole, single throw) switch type
• 3 amp rated for typical spa control board connections
• Durable plastic threaded body with internal diaphragm
• Part no. 3903-BP

Returns & installation: Confirm your spa's pressure switch fitting and electrical rating requirements match before ordering, as electronic parts are non-returnable once installed. Installation should be performed with power disconnected, per your spa's service manual.

FAQ

Q: How do I know if this switch needs replacing?
A: A pump that won't engage, or a heater that fails to activate despite adequate water flow, can indicate a failing pressure switch.

Q: What does the 1-5 PSI rating mean?
A: The switch is factory-set to activate at approximately 1.5 PSI once sufficient water flow is present, confirming safe conditions before heater operation.