Quick Answer: Winterizing a hot tub means one of two things, and picking the wrong one is the expensive mistake: either fully drain it — blow out the pump, heater, and jet lines with a wet/dry vacuum, then add propylene glycol antifreeze (never automotive antifreeze) to the filter well and jets as backup — or keep it running all winter at a lower setpoint, which most plug-and-play and hardwired spas are actually built for. The one thing you can never do safely is leave a spa filled with water and powered off in freezing weather; that combination is what cracks pumps and splits pipes.
Every fall, hot tub forums fill up with the same expensive mistake: an owner shuts the breaker off for winter storage without draining first, and comes back in spring to a cracked pump housing or a split heater manifold. Winterizing isn’t one universal process — it’s a decision between two very different paths depending on what kind of spa you own, and getting that decision right matters more than any single step in the process itself.
Winterizing by the numbers
- 1-2 gallons of propylene glycol antifreeze covers a small inflatable spa’s filter well and jet lines; larger hard-shell spas typically need 3-6 gallons, per the standard spa-industry winterizing guidance documented by SwimUniversity and pool-and-spa antifreeze suppliers.
- Propylene glycol, not ethylene glycol — pool, RV, and marine antifreeze is the only safe type for a spa’s plumbing; automotive antifreeze is ethylene glycol, which is toxic and never belongs anywhere near water a person will later soak in.
- 10-15 seconds per jet and union, repeated until no more water comes out, is the standard blow-out interval spa winterizing guides recommend using a wet/dry shop vac set to blow rather than suction.
- 2-3 hours is the realistic time budget for a full winterization once the tub is already drained, according to SwimUniversity’s step-by-step process — most of that is the repeat-until-dry line-blowing step, not the draining itself.
Decide first: drain it, or keep it running?
| Spa type | Recommended winter approach | Why |
|---|---|---|
| Inflatable (Intex, SaluSpa) — no FreezeShield/winter mode | Full drain, blow out lines, antifreeze, deflate for storage | Thin PVC and a small sealed pump-heater unit aren't built to run through a hard freeze unattended |
| Inflatable with freeze-protection mode (e.g. SaluSpa St. Moritz FreezeShield) | Keep running through mild winters; full drain if leaving it unattended for weeks | Freeze-protection modes cycle the pump automatically, but they still assume someone's home to notice a fault |
| Plug-and-play hard-shell (AquaRest, Lifesmart) | Keep running at a lower setpoint all winter | Full-foam insulation and a roto-molded shell are designed for continuous winter operation |
| Hardwired hard-shell, any brand | Keep running — this is the default use case, not an edge case | 240V hard-shell spas are engineered specifically to stay in service through freezing climates |
| Any spa type, house going unoccupied for weeks | Full drain and winterize — don't rely on power staying on | A single breaker trip or power outage on a filled, unheated spa is enough to freeze and crack it |
The pattern: the more insulated and purpose-built the spa, the more likely “just keep it running” is the right call — see our best inflatable hot tub for winter roundup for which inflatable models include a real freeze-protection cycle versus which need a full seasonal drain instead. If you’re not sure which category your tub falls into, check your model’s manual for a freeze-protection or winter mode setting before assuming either path.
Full winterization: step by step
- Start above freezing. Pick a day the forecast holds above 32°F for a few hours — racing a hard freeze mid-drain is how a line gets missed.
- Drain completely. Use the tub’s drain valve or a submersible pump; see our how to drain a hot tub guide for the full step-by-step, including where wastewater is and isn’t allowed to go.
- Blow out every line. Set a wet/dry shop vac to blow (not suction) and hold it over each jet, the filter standpipe, and any union fitting for 10-15 seconds, repeating until no more water comes out. This is the step most owners rush — a line that still holds a cup of water is enough to crack a fitting.
- Add propylene glycol antifreeze. Pour it into the filter well, the footwell, and any jet or fitting water could still be trapped behind — 1-2 gallons for a small inflatable, 3-6 gallons for a larger hard-shell spa. This is backup insurance in case the blow-out step missed a low point in the plumbing, not a replacement for it.
- Wipe the shell or liner dry, then close and secure the cover. For an inflatable being stored indoors, let it dry fully before deflating and folding — trapped moisture in a folded liner grows mildew over winter.
Propylene Glycol Pool & Spa Antifreeze (RV/Marine-Safe)
- The only antifreeze type safe for spa plumbing — automotive (ethylene glycol) antifreeze is toxic and never belongs in this job.
- Keep 2-4 jugs on hand; a hard-shell spa's larger plumbing runs through antifreeze faster than an inflatable's.
- Doubles as RV plumbing antifreeze if you own one — buy the multi-pack and use the rest there.
Every winterizing job needs a wet/dry vacuum on hand before you start, not halfway through — start a free Amazon Prime trial and a shop vac or the antifreeze itself can be on your doorstep the next day instead of a last-minute hardware store run.
Wet/Dry Shop Vacuum (Blow + Suction, 4-6 Gallon)
- Most shop vacs include a blow port specifically for this job — check before buying if you don't already own one.
- A 4-6 gallon size is enough for spa winterizing and stays easy to store the rest of the year.
- Reusable every fall, and useful for garage cleanup the other eleven months.
Keeping it running instead: what that actually requires
If your plug-and-play or hardwired spa is staying in service, winterizing becomes much simpler: confirm the cover is in good condition and fully secured (a worn or waterlogged cover is the single biggest cause of a winter spa running up your electric bill or losing the fight against a hard freeze), keep the setpoint at a level the tub can maintain efficiently rather than shutting it down between uses, and never cut power to a filled tub for an extended trip. Our hot tub cover guide and cover lock guide cover the sealing and wind-security side of this, and our hot tub wiring guide covers where the dedicated GFCI circuit that a winter-running spa depends on should sit. If you’re leaving home for more than a few days in freezing weather, treat that as the unoccupied-house scenario in the table above and consider a full drain instead of trusting the power to stay on.
The bottom line
Winterizing a hot tub is really two different jobs wearing one name: a full drain-and-antifreeze process for a basic inflatable spa going into storage, or simply keeping a well-insulated plug-and-play or hardwired spa running all winter with a secure cover. The mistake that actually causes damage is neither of those — it’s leaving a filled spa powered off in freezing weather, which cracks pumps and splits plumbing every single winter somewhere. Not sure which inflatable models handle a real winter without a full drain? Our best inflatable hot tub for winter roundup covers which ones include a genuine freeze-protection cycle. And once spring comes, our hot tub maintenance guide picks the routine back up from the first refill.