Hot Tub Error Codes Explained: What Your Display Is Telling You

Many topside display codes are not faults at all. Some simply tell you what the spa is doing, such as priming after a refill or heating in Economy mode. Others are protective warnings that switch off part of the system until you sort out the cause. Autumn and winter are when owners see codes most often: water changes before the cold weather lead to priming messages and airlocks, and the first frosts can bring up the freeze protection warning.

This guide explains the messages our Balboa-controlled hard-shell spas show and what you can safely check yourself. Some models use a Gecko control system, and patio and inflatable spas have their own codes, so if you see something not listed here, look it up in the manual for your model on our Owners Manuals & Downloads page.

Safety first

Switch the spa off at the isolator before you remove a cabinet panel or take out a filter. Never open the control box, as there are no user-serviceable parts inside. If the RCD trips, reset it once at most. If it trips again, leave the power off and call a qualified electrician.

Messages that are normal

Numbers at power-up

When the spa is first switched on, four sets of numbers flash on the display. The last number in the sequence is the incoming power reading, which an electrician can use to check the spa is wired correctly.

Pr: priming mode

After power-up the spa runs a priming routine for a few minutes and shows Pr. Press each pump button slowly in turn so that each pump primes, and set the temperature once Pr clears. Do not run a pump for more than a minute if no water is moving through it. If a pump hums but the jets stay still, there is probably an airlock, which is common after a drain and refill. Our weak or dead jets guide shows how to clear one.

St, Ec and SL: heating modes

Depending on the panel, these appear as St or Std, Ec or Ecn, and SL or SLP.

• Standard keeps the water at your set temperature all the time.
• Economy heats to the set temperature, but only during filter cycles.
• Sleep heats to within about 10°C of the set temperature, and again only during filter cycles.

If the water feels cooler than the set temperature, check the mode before anything else. Our hot tub not heating guide covers the other common reasons for cool water.

Dashes instead of a temperature

A display showing dashes means the spa does not currently know the water temperature. This happens in Economy or Sleep mode between filter cycles, because the pump has not run recently. The temperature reading is only accurate once the pump has been running for at least two minutes, so switch to Standard mode or turn the jets on, and wait.

FC or FILC, and F2 to F8: filter cycles

These show the filter cycle length. The first cycle starts six minutes after the spa is powered up and the second 12 hours later. Each can be set to 2, 4, 6 or 8 hours, or to continuous filtration (FC or FILC). The default is 2 hours. Keep to F2 or F4 for everyday use. F8 or continuous filtration can help clear cloudy water, but use it for short periods only, as long cycles on high settings can overheat the pump.

The winter warning: ICE or IC

ICE or IC is the freeze protection warning. If the sensors detect water below 6.7°C in the heater, the pump switches on automatically to keep water moving, and on some models the second pump and blower run too. The equipment stays on until four minutes after the water reaches 7.2°C, and then the spa starts heating as normal. This is why you may hear the pumps start up on their own on a frosty night, and our guide to what hot tub noises mean covers the other sounds that are normal.

You are most likely to see ICE when filling the spa on a cold day. Always fill with cold water from a garden hose, never hot water. If the warning is slow to clear after filling, adding a little warm water with a bucket helps lift the temperature past 7.2°C.

Freeze protection only works if the spa has power. If you are going away this winter, set the spa to Economy or Sleep mode rather than switching it off. Our winter hot tub tips explain what to do if a power cut hits during a cold snap. Our checklist for leaving your hot tub while you're away covers the rest of the preparation.

Fault messages

OH or HH: overheat

The sensors in the heater have detected water above 43°C, and the spa has shut itself off. Do not get in. Take the cover off, let the water cool, then reset the spa at the breaker. If the message comes back, put a thermometer in the water and compare its reading with the display. Tell us both figures when you call, as it helps us diagnose the problem.

FLO, FL, LF, HL or HFL: low flow

These all point to a problem with water flow through the heater, which is monitored by a pressure switch. If the message alternates with the temperature, work through these checks with the power off:

• Top up the water level. If it falls too low, the pump draws in air.
• Clean the filter, or replace it if it is worn. Hard-shell filters last 6 to 12 months, and our Glacier Antimicrobial 50 sq ft filter is best replaced every 6 months for top performance, or up to 12 months for economy. Our hot tub filters range lists the right cartridge for each model.
• Make sure the slice valves either side of the pump and heater are fully open.
• Check the pump is primed, with no airlock.

If FL shows constantly and nothing on the spa works, the pressure switch may be stuck. That needs an engineer.

dr or dRY: dry heater

The control system has not detected enough water in the heater, so it shuts the spa down. It will not restart until you reset it manually. Before you do, check the water level, the filter and that all jets and valves are open, using the same checks as for low flow.

SA, Sb, Sn or SnS: sensor messages

The heater has two sensors that regulate temperature and check the flow. If one stops working, or the two disagree, a sensor message appears and the spa shuts down. They can appear briefly after an overheat, when no repair may be needed. Take the cover off, let the temperature drop, then reset the breaker. If the message returns, the sensor or circuit board needs testing by an engineer.

A blank display

If the panel is dark and nothing responds, check whether the RCD has tripped. Do not keep resetting it. Our guide to a hot tub that keeps tripping the RCD explains what to note down and when to call an electrician.

Before you call us

If a fault code keeps coming back, note down your model and serial number, the exact code, when it started, and any recent water changes or maintenance. A photo of the display helps too. Our hot tub servicing team can diagnose and repair control, heater and flow faults, or call us on 01293 824094 and we will talk you through it.

Quick reference

Code	What it means	What to do
Pr	Priming after power-up	Prime each pump, then set the temperature
St / Ec / SL	Standard, Economy or Sleep heating mode	Switch to Standard if the water is too cool
Dashes	Temperature not yet known	Run the pump for 2 minutes
FC / FILC	Continuous filtration	Use short term only; F2 or F4 for everyday
ICE / IC	Freeze protection running	Leave the power on and let it clear
OH / HH	Water above 43°C	Stay out, cover off, cool, reset
FLO / FL / LF	Low flow through the heater	Water level, filter, valves, airlock
dr / dRY	Not enough water in the heater	Same checks, then reset manually
SA / Sb / Sn	Sensor fault	Cool, reset; call us if it returns