Hot tub air lock after a refill?
Good news: an air lock after a drain-and-refill is often something you can clear yourself in a couple of minutes — briefly loosen the pump union to burp the trapped air, or run the jets on high. Here's exactly how, and when a stubborn one is really a pump or prime problem to call us for.
from $359 · $100 diagnostic, paid up front & credited
Trapped air is blocking the pump from priming
After you drain and refill a hot tub, air gets trapped in the plumbing between the pump and the jets. A spa pump is designed to move water, not air — so when a pocket of air sits in the wet end, the impeller just spins against it without grabbing a solid column of water. The motor runs, but no flow reaches the jets. That's an air lock, and it's one of the few hot tub faults you can often fix without a tech.
You'll usually recognize it because it appears immediately after a refill: the pump sounds like it's running normally (or surging), the jets are dead or sputtering, and you may get a flow-related code as the heater can't sense water. Nothing is broken — the air simply needs somewhere to go so water can take its place and the pump can prime.
We're happy to tell you straight: most air locks don't need a service call. The fixes below clear the great majority of them. We'd rather you get back in the water tonight than pay us for two minutes of burping a union. What follows is exactly how to do it — and the honest signs that say the problem is no longer just air.
Two ways to burp the air — try these first
Top the water
Make sure the water sits above the skimmer intake. If it's low, the pump pulls in more air and the lock won't clear no matter what you do.
Run jets on high
Switch the affected pump to high speed and let it run for 30–60 seconds. Often the surge pushes the trapped air out through the jets on its own.
Burp the pump union
If high speed doesn't do it, power off, then slightly loosen the threaded union on top of the pump until you hear air hiss out and water appears. Snug it back up and restart.
Cycle and check
Power-cycle the pump and confirm steady flow. Repeat the union burp once if it's stubborn — sometimes it takes two tries to clear it all.
These steps clear most air locks. If flow still won't return after a couple of tries, it's no longer just trapped air — that's where we come in.
When it's NOT just an air lock — call us
If you've topped the water, run the jets on high and burped the union more than twice and flow still won't hold, the problem has moved past trapped air. A pump that won't hold prime, a worn wet end losing suction, or a failing circ pump behave like a permanent air lock. If a refill triggers an air lock every single time, or the pump runs but never grabs water, that's a prime or pump fault we should diagnose.
Upfront pricing, published
Clearing an air lock is free advice — but if the pump genuinely won't hold prime, here's what a repair runs, confirmed at your $100 diagnostic.
Not quite your symptom?
Answers before you call
Top the water above the skimmer, run the affected pump on high for 30–60 seconds, and if that doesn't clear it, power off and slightly loosen the union on top of the pump until air hisses out and water appears, then snug it back and restart. Most air locks clear this way.
Yes, if you power the pump off first and only loosen the union a little — just enough to let air escape and water seep out, then hand-tighten it back. Never open it with the pump running. If you're not comfortable, we'll handle it.
An occasional air lock after a refill is normal. But if it happens every single time, or the pump runs and never grabs water, the pump may not be holding prime — often a worn wet end or a failing circ pump that should be diagnosed.
Call when you've topped the water, run the jets on high and burped the union more than twice and flow still won't hold, or when an air lock returns constantly. At that point it's a prime or pump fault, not just trapped air.
From $359 for a seal or wet-end repair, up to a circulation pump replacement if the pump can't hold suction. Clearing a simple air lock is free advice. You get the flat price before any work.
Burped it twice and still no flow? That's our cue.
Starting at $359. Same-day. $100 diagnostic credited to your repair.
Tell us what happens after a refill — we'll call back within the hour
No call center. Just a local tech who'll confirm whether it's prime or the pump and quote the price before any work.
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We'll call you back within the hour. Hot tub out cold right now? Call us at (561) 794-1557.