Pool Error Codes

Raypak PRS: Low Water Pressure Fault

PRS means the water pressure switch on your Raypak heater hasn't sensed the flow it needs, so the burner won't fire.

Your Raypak heater's display is showing PRS and the burner refuses to light, even though the pump is out at the pad running. This is one of the most common codes on Digital ASME and low-profile Raypak heaters, and it's also one of the more DIY-friendly ones — the switch itself is fine most of the time, it's just not seeing the water movement it's built to check for before it lets the gas valve open.

Medium severity

Applies to: Raypak Digital ASME and low-profile residential gas pool/spa heaters (106A-406A series)

What it means

Every Raypak gas heater has a water pressure switch wired into its safety circuit specifically so the burner cannot ignite without water actively circulating through the heat exchanger. PRS shows up the instant the control board checks that switch and finds it open — in other words, it isn't a guess about a bad part, it's the heater reporting that it never got confirmation of adequate flow. Until that switch closes, the heater sits idle rather than risk firing a burner into a dry or nearly-dry exchanger.

Likely causes

What you can check yourself

  1. Confirm the pump is on and valves to the heater are fully open
  2. Clean/backwash the filter and clear the pump strainer basket
  3. Bleed trapped air from the filter's air relief valve
  4. Clear the fault and retry once flow looks normal
Call a professional if…

If flow is verified normal at the pad but PRS keeps returning, have a technician test and likely replace the pressure switch.

Sources

Related

This site is an independent reference, not a substitute for a licensed pool professional. Gas pool heaters can leak carbon monoxide and cause fire; pump and heater electrical circuits carry mains voltage. Anything involving the gas line, burner assembly, or house wiring should be handled by a licensed technician or electrician.