AquaTerra Spa Error Messages Explained: OH, HL, FLO, AOH, PRR, and What to Do About Each

When your AquaTerra spa displays a short code instead of the water temperature, it is not being cryptic. It is telling you exactly what the control system has detected, and in many cases what it has done to protect the spa. A few of these messages mean you should stay out of the water until things cool down. Others point to a simple fix like a dirty filter or a low water level. Only a few require a service call.

This guide explains every diagnostic message listed in the AquaTerra owner's manual, what to do about each, and how to troubleshoot the most common problems that do not produce a message at all.

Safety First When a Message Appears

Two of these messages, OH and HL, mean the water or heater is hotter than it should be. Treat both as a firm signal to stay out of the spa, and keep children and guests out too, until the water has cooled and the message has cleared.

First: Codes You See at Power-Up Are Normal

When an AquaTerra spa is first powered up, the control system runs a startup mode of about two minutes, and different codes appear on the screen during that time. That is normal. Once startup completes, the display shows the actual water temperature, the spa begins heating, and the first filter cycle starts. Wait out those two minutes before assuming something is wrong.

The Diagnostic Messages

No Message on the Display

Meaning: Power to the spa has been cut off. The control panel is disabled until power returns, and your settings are preserved.

What to do: Check the household breaker and the GFCI (the cord GFCI on a 110 volt spa, or the subpanel GFCI on a 230 volt spa). See the no component operation section below.

HL: Heater High Limit

Meaning: The system shut the heater off because the temperature at the heater reached 122 degrees F.

What to do: Do not enter the water. Remove the spa cover and let the water cool. Then shut the power off and power the spa up again to reset the system. If the spa does not reset, turn off the power and call for service. Because an HL condition usually involves poor flow through the heater, check for a dirty filter and low water level before restarting.

OH: Overheat

Meaning: The water temperature in the spa has reached 108 degrees F. The spa is deactivated.

What to do: Do not enter the water. Remove the cover to let the water cool. The control system resets itself once the water drops below 104 degrees F, after which you can push any button on the topside control to reset. If it keeps happening, call for service.

AquaTerra explains how water can overheat. When water temperature rises about 2 degrees F above the set point, the jet pump stops to reduce frictional heating. If temperature keeps rising past 108 degrees F, the spa goes into OH. Extreme weather is a common cause. AquaTerra notes that prolonged ambient temperatures above 106 degrees F can push water temperature high enough to trigger OH, and suggests reconsidering the spa's location to reduce heat around it, such as adding shade.

AOH: Ambient Overheat

Meaning: The temperature inside the equipment compartment has reached 194 degrees F, raising the control system's internal temperature above normal limits.

What to do: Open the equipment compartment and wait until the error clears. Make sure nothing is blocking airflow around the spa cabinet, and avoid packing insulation, stored items, or landscaping tightly against the equipment side.

FLO: No Flow Detected

Meaning: The control system expects water flow but does not detect it.

What to do: This is the message owners can fix most often. Make sure the jet pump is running and water is flowing. Clean the filter, make sure water valves are open, and confirm the water level is correct. If the problem persists, call for service.

PRR: Temperature Probe Problem

Meaning: The system detected a problem with the temperature probe.

What to do: Call your dealer or service provider. This involves the control system and is not an owner repair.

UPL: No Configuration Software

Meaning: No low-level configuration software has been installed in the system.

What to do: Call your dealer or service provider.

Problems Without a Message

Nothing Works at All

AquaTerra's checklist: Is there power to the spa? Is the household circuit breaker tripped? Is the subpanel GFCI (230 volt) or cord GFCI (110 volt) tripped? If any of these is the case and resetting does not solve it, contact customer service or a qualified electrician. A GFCI that will not stay reset can indicate a ground fault.

The Pump Runs but No Water Comes From the Jets

This usually happens after draining and refilling, when the pump is not properly primed and air is trapped in the plumbing. AquaTerra's fix is to press the Jets button several times, never leaving the motor running for more than 5 to 10 seconds at a time with no water coming from the jets. The short bursts help push air out without overheating the pump.

Poor Jet Action

1. Press the Jets button to confirm the pump is on.
2. Rotate all air control valves counterclockwise and watch for stronger jet action.
3. Check that the water level is halfway between the top of the spa and the top of the gray filter ring.
4. Clean the filter if it is dirty.
5. Make sure all jets are in the open position.

Water Too Hot

Check the set temperature on the topside control first, then look for an OH or HL message and follow the steps above.

Test Your GFCI Regularly

AquaTerra recommends testing the GFCI before each use. On a 110 volt spa, press TEST on the cord GFCI with the spa running. The spa should stop and the GFCI indicator should go out. Wait 30 seconds, then press RESET. On a 230 volt spa, press TEST on the subpanel breaker, wait 30 seconds, then switch it fully off and back on. If the GFCI does not behave this way, disconnect power until the problem is corrected. AquaTerra notes that not waiting the full 30 seconds can make the Power indicator blink, in which case you simply repeat the test.

Preventing Error Messages Before They Happen

Almost every message in this guide traces back to one of three things: heat, flow, or power. A simple routine keeps all three in check.

• Keep the filter clean. Monthly cleaning and replacement every six to eight months prevents most FLO and HL messages.
• Watch the water level. Low water starves the pump of flow and can cause air to be drawn in. Top off as evaporation lowers the level.
• Purge air after every refill. Use short bursts of the Jets button until water flows steadily.
• Give the equipment room to breathe. Keep the area around the equipment side clear to prevent AOH, especially in summer.
• Plan for heat. In very hot climates, shade the spa and lower the set temperature during heat waves to avoid OH.
• Test the GFCI. Regular testing confirms your most important safety device is working.

Keeping a short log of any messages you see, along with the date and weather, also helps a technician spot patterns if you ever need service.

When to Call for Help

AquaTerra's manual is clear that the control box has no user-serviceable parts. Call for service for PRR or UPL messages, an HL that will not reset, a GFCI that will not stay on, repeated FLO or OH messages after you have cleaned filters and corrected the water level, or any water leaking in the equipment compartment.

Frequently Asked Questions

What does OH mean on an AquaTerra spa?

OH means the water reached 108 degrees F and the spa has shut down. Do not enter the water. Remove the cover to let it cool, and the system resets once the water drops below 104 degrees F.

Why does my spa show strange codes right after I turn it on?

That is the normal startup mode, which lasts about two minutes. Once it finishes, the display shows the water temperature and the spa begins heating.

What is the difference between HL and OH?

HL means the temperature at the heater reached 122 degrees F, usually from poor flow. OH means the spa water itself reached 108 degrees F. Both mean stay out of the water.

How do I fix a FLO error?

Clean the filter, check the water level, make sure valves are open, and confirm the pump is running. If it persists, call for service.

Why won't my jets work after refilling?

The pump likely has an air lock. Press the Jets button several times in short bursts of no more than 5 to 10 seconds until water flows.

Most AquaTerra messages are protective, not catastrophic. Stay out of hot water when you see OH or HL, fix flow when you see FLO, give the equipment air when you see AOH, and call a professional for PRR and UPL. With a clean filter and the right water level, many of these messages never appear at all.