Troubleshooting guide
Hot tub airlock after a refill
After a drain and refill, air can get trapped in the pump and plumbing. Water won't move, the heater won't start, and the spa may show a flow code. It's usually fixable in a few minutes.
How priming mode works (Balboa)
Balboa's TP500S guide says the system enters Priming Mode each time it powers up. It lasts about 4 to 5 minutes, the heater is disabled during it, and you run each pump to push the air out. If the pumps haven't primed after 2 minutes and no water is flowing from the jets, turn the pumps off and repeat. Turning the power off and on starts a new priming mode.
Important: Balboa says a pump should not run without priming for more than 2 minutes, and never beyond the end of priming mode.
Bleeding air at the pump
Hot Spring's manual gives the standard fix for a pump that runs but moves no water after a refill:
- Turn off power to the spa at the breaker and remove the equipment compartment door.
- Loosen the union on top of the pump to let the air escape. When water appears, hand-tighten the union.
- Turn the power back on, run the pump, and check the union is tight enough not to leak. Reinstall the door.
Gecko's guide describes the same idea for its FLO error: if air bubbles are trapped (the pump may sound abnormal), slowly unscrew a union nut to free the air, then tighten it back.
Refill tips that prevent problems
- Fill first, then power. Hot Spring warns not to power up the spa until it's filled, because heaters and controls can be damaged.
- Mind the fill water temperature. Hot Spring says its refill water must be between 50 and 70°F to avoid tripping the high-limit, and recommends not refilling when the air is below 50°F.
- Fill through the filter compartment if your manual says to. Many do, because it pushes water through the plumbing and helps prevent airlocks.
Still no flow?
If priming doesn't work, a valve may be closed, a union or slice valve may be partly shut, or the pump may have a problem. A tech on video can walk you through the equipment bay (power off) and spot it.
Common questions
How do I get an airlock out of my hot tub?
Use your control's priming mode to run each pump in short bursts. If that doesn't clear it, turn the power off at the breaker, loosen the union on top of the pump until water appears, hand-tighten it, then power up and try again.
How long should priming mode last?
On Balboa systems, about 4 to 5 minutes, and you can exit early once the pumps are primed. Don't let a pump run without water flowing for more than 2 minutes.
Why did my hot tub stop working after I refilled it?
Common reasons are an airlock, a high-limit trip from very cold fill water, or the heater waiting until priming mode ends. Check the topside message and follow your manual's priming steps.
Related guides
Weak jets or pump not working
Weak, surging or no jets: water level, filters and air first.
Read the guideHot tub not heating
Jets run but the water stays cold. Usually it's flow, not the heater.
Read the guideGecko error codes
FLO, HL, OH, Prr, AOH and UPL, from Gecko's troubleshooting guide.
Read the guideWinterizing and freeze protection
Keep it running, or drain and winterize it properly. No car antifreeze, ever.
Read the guideSources
- Balboa Water Group, TP500S / TP600 system user guide (42339 rev A1): priming mode, freeze protection, GFCI trip test and message codes
- Hot Spring Spas (Watkins Wellness), Hot Spot collection SX/TX owner's manual: GFCI and high-limit checks, priming, drain & refill, winterizing and troubleshooting tables
- Gecko Alliance, Y-series and in.xe troubleshooting guide (9919-101313-D, rev. July 2023): FLO, HL, OH, Prr, AOH and UPL messages
Brand names belong to their owners. Hot Tub Helpline isn't affiliated with or endorsed by any manufacturer. Steps and codes vary by model and year, so always check your own owner's manual.