Jacuzzi FL1 & FL2 Error: What It Means and How to Fix It

Reviewed by the Spa Store parts team, serving hot tub owners since 1994. Last updated October 2026.

Quick answer: FL1 and FL2 are water-flow errors on 2014-and-newer Jacuzzi J-300 hot tubs (J-315 through J-385). In both cases the heater shuts off to protect itself.

FL1No water flow detected while the circulation pump runs. Usually a dirty filter or trapped air.

FL2The flow switch reads flow while the pump is off. Usually a failed flow switch.

Covers J-315, J-325, J-335, J-345, J-355, J-365, J-375 and J-385 models built in 2014 or later. Not sure which you have? See our J-300 Series troubleshooting page.

Fix FL1 yourself: 5 checks, no tools needed

  1. Pull the filter and let the air out. Trapped air in the filter cartridge is the most common cause. Lift the filter out, let it burp, and put it back.
  2. Check the water level. If it's below the skimmer opening, the pump draws air instead of water. Top it up.
  3. Clean or replace the filter. A clogged cartridge starves the pump. If it's over a year old or won't rinse clean, replace it.
  4. Check the skimmer. Make sure the floating skimmer moves freely and isn't stuck shut.
  5. Look for blockages at the filter wall fitting, such as leaves or a stray cap.

Then restore power and wait a few minutes. If FL1 clears, you're done.

When to call a technician

If FL1 keeps coming back, or you're seeing FL2, the next steps involve the equipment bay and live high-voltage wiring.

Safety first. Turn off power at the breaker before opening anything, and leave electrical testing to a qualified spa technician.

A technician will typically:

  • Check that the flow switch arrow points away from the heater, in the direction of flow.
  • Remove the switch and clean out debris. This fixes most cases.
  • Test the switch with a meter, then check the wiring harness and circuit board.
Technician tip: Count the turns it takes to unscrew the flow switch, and reinstall it with the same number of turns. Threading it in too far can make the internal arm stick against the bottom of the fitting, which brings the error right back.

Parts that fix FL1 and FL2

Part Fits (2014+) Spa Store Item #
Filter cartridges All J-300 Shop filters
Flow switch J-335, J-345, J-355, J-365, J-375, J-385 0400652
Flow switch J-315, J-325 2580656
Circuit board (last resort) J-335 to J-385 3920066
Circuit board (last resort) J-315, J-325 5920066

Start with the cheapest likely fix: filter first, then flow switch, then board. Most FL errors never get as far as the circuit board.

Scan to text photos of your part to Spa Store

Not Sure If This Fits?

Get a Guaranteed Exact-Fit Match From Our 32-Years Of Expertise.

Over 300,000 Customers Served.

Text Photos For Expert Review:

858-215-4460 (TEXT ONLY)

Mon-Fri 9-5 PST

Frequently asked questions

Can I still use my hot tub with an FL1 error?

The jets may run, but the heater stays off until the flow problem is fixed, so the water will slowly cool.

Why did FL1 show up right after I refilled my tub?

Refills often trap air in the plumbing or filter. Pull the filter to let the air escape, and check that the water level is high enough.

Is FL2 ever caused by a dirty filter?

Rarely. FL2 usually means the switch is stuck closed or has failed, so replacing the switch is the usual fix.