DIY Error Codes

Jandy JXi gas pool heater Fault CHECK FLOW

The heater is not sensing enough water pressure, so it will not fire. Start with the pump, filter and valves.

Make sure the pump is running, clean the filter and check valve positions. If CHECK FLOW stays, call a qualified technician.

Start the fix →When to call a pro ↓
Full answer & models

Jandy JXi CHECK FLOW means the heater senses too little water pressure. Check the pump, filter, valves and return fittings; if it stays, call a pro.

Applies to: JXi 200JXi 260JXi 400
Also searched as: Jandy heater CHECK FLOW, Jandy JXi check flow, Jandy pool heater check flow fault, Jandy heater flow error

Gas appliance. Owner checks only; Jandy says a qualified professional service technician must do all service.
Why
Jandy, what to do if you smell gas: immediately switch off main gas supply; do not try to light any appliance; do not touch any electrical switch; do not use any phone in your building; immediately call your gas supplier from a neighbor's phone and follow the gas supplier's instructions; if you cannot reach your gas supplier, call the fire department. Installation and service must be performed by a qualified installer, service agency or the gas supplier. Jandy: ELECTRICAL SHOCK HAZARD. This heater contains wiring that carries high voltage. Contact with these wires may result in severe injury or death. Jandy servicing safety: service procedures can be hazardous because they involve fuel gas, electricity, moving parts and procedures which require testing or temporary bypass of safety controls, so the heater must be serviced only by a qualified professional service technician. Improper installation or maintenance can cause nausea or asphyxiation from carbon monoxide in flue gases which could result in severe injury, or death.

What CHECK FLOW means

The heater is not sensing enough water pressure, so it will not fire. Start with the pump, filter and valves.

More detail
Jandy's JXi manual (Section 10.2, Service Diagnostic Messages, p. 47) lists CHECK FLOW with these possible causes: pump is not running, low pump pressure, pressure switch fault, or variable speed pump set too low. Section 1.8 (p. 7) says the water pressure switch senses whether water is available to the heater by measuring back pressure at the header inlet; if insufficient pressure is detected, the display shows "Check Flow" and combustion stops.

5-minute checks

Fix it step by step

Step 1 of 5

  1. Make sure the pump is running

    • 5 min
    • None
    • Caution

    Safety: Gas appliance. Owner checks only; Jandy says a qualified professional service technician must do all service.

    Pump not running is the first cause Jandy lists.

    More detail

    Make sure the pump is running.

    Jandy remedy (p. 47): check breakers and power source, recheck wiring, set time clock and current time. Checking the breaker and setting the time clock are owner tasks; leave any wiring to a qualified technician. Electrical shock hazard. Jandy: this heater contains wiring that carries high voltage. Leave all wiring to a qualified technician.

    Did the code clear?

  2. Clean the filter and check valves

    • 20 min
    • None
    • DIY

    Low pump pressure is the next cause.

    More detail

    Clean the filter and check valves.

    Jandy remedy (p. 47): clean filter or clear blockage, and check the position of valves in the plumbing system.

    Did the code clear?

  3. Check the return fittings

    • 5 min
    • None
    • DIY

    Jandy: return eyeball fittings must be installed.

    More detail

    Check the return fittings.

    Jandy remedy (p. 47): make sure return eyeball fittings are installed on the wall of the pool.

    Did the code clear?

  4. Variable speed pump: raise the speed

    • 5 min
    • None
    • DIY

    Jandy lists a pump set too low as a cause.

    More detail

    Variable speed pump: raise the speed.

    Jandy lists "variable speed pump set too low" as a cause, with the remedy "adjust variable speed pump" (p. 47). Jandy's specifications list a minimum water flow rate of 30 gpm (76 lpm) (Section 1.5, p. 5). Follow your pump's own manual to change its speed.

    Did the code clear?

  5. Call a qualified service technician

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a qualified service technician.

    Jandy's remaining remedies (p. 47), adjusting or replacing the pressure switch, are technician work. Jandy: refer to qualified service personnel. Jandy (Section 11, p. 48): call a qualified service technician to perform all service and repairs on the heater. Do not open the heater cabinet yourself.

    Still showing CHECK FLOW?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still CHECK FLOW after step 5? call a pro.

Call a pro if…

  • You smell gas (switch off the main gas supply if you can, then call your gas supplier from a neighbor's phone).
  • CHECK FLOW keeps coming back after the owner checks.
  • Anything that needs the heater cabinet opened, wiring checked, or gas pressure tested.

FAQ

What does CHECK FLOW mean on a Jandy JXi?

The water pressure switch did not sense enough back pressure at the header inlet, so combustion stops (p. 7). Jandy lists pump not running, low pump pressure, a pressure switch fault, or a variable speed pump set too low (p. 47).

What flow does a JXi heater need?

Jandy's specifications table (Section 1.5, p. 5) lists a minimum water flow rate of 30 gpm (76 lpm).

Source: Jandy JXi Gas-Fired Pool and Spa Heater Installation & Operation Manual (H0574300 Rev M), Section 10.2 Service Diagnostic Messages (p. 47); Section 1.5 (p. 5); Section 1.8 (p. 7); safety, pp. 1, 32, 38 and 48. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Jandy.