How to Winterize a Hot Tub: Step-by-Step Guide
Winterizing a hot tub takes 2-3 hours: add a system flush product and run jets for 30 minutes, then drain completely, remove and clean the filter, blow out all plumbing lines with a wet/dry shop vac, wipe down surfaces, and cover with a lockable winter cover. Skip any of these steps and water left in the lines can freeze, expand, and crack the plumbing, repairs run $500-2,000 or more.
If you’re looking for the basics of year-round care, start with our complete hot tub maintenance guide first.
Video guide
Video: “HOT TUB MAINTENANCE For Beginners” by Swim University
Should you winterize or keep your hot tub running?
Before grabbing a shop vac, confirm that winterizing is actually the right call. A lot of owners, particularly in the South or Pacific Northwest, waste a weekend closing a spa that should just keep running.
Winterize if: temperatures will drop below 32°F for extended periods AND you won’t use the spa for 6 or more weeks. Running a spa with no users is an unnecessary energy expense, but that’s a different problem from freeze risk.
Keep running if: you’ll use it occasionally through winter, or you live in a mild climate where hard freezes are brief or rare. A well-insulated spa running at 100°F circulates continuously and won’t freeze even in light freezes, the pump and heater are the freeze protection.
The rule we tell every owner: never leave a powered-off hot tub with water in it below freezing. That’s the scenario that causes damage. Either keep it running or winterize completely. There’s no safe middle ground. The DOE hot tub energy efficiency in winter{:target=“_blank”} guidance confirms that continuous operation is often the more cost-effective choice in mild climates.
Be honest with yourself about your climate. If you’re in Nashville and freezes last 2-3 days, winterizing is probably more disruption than it’s worth. If you’re in Minnesota and closing the cabin until May, winterize.
What you’ll need
Gather everything before you start. Having to stop mid-drain to find supplies extends the job significantly.
- Wet/dry shop vacuum (on exhaust/blow setting, this is how you clear the lines)
- System flush or purge product (Ahh-Some, Natural Chemistry Spa Purge, Swirl Away)
- Garden hose
- Submersible pump (if your spa doesn’t have a built-in drain spigot)
- Non-toxic propylene glycol spa antifreeze (optional, for any lines you can’t fully blow out)
- Large sponge or shop towels for residual water in footwell
- Filter cleaning supplies (see our hot tub filter cleaning guide for the full soak process)
- Heavy-duty winter spa cover or lockable cover cable clips
Do not use automotive antifreeze. It’s ethylene glycol, toxic to people, pets, and plants. Spa antifreeze is propylene glycol, which is food-safe.
Step-by-step: how to winterize a hot tub
Step 1: shock your hot tub, then add the system flush product
Before draining, shock your hot tub before draining to kill any bacteria in the water. Once done, with the spa still full of water and jets running, add your system flush product per label directions and run jets on all settings for 30 minutes. According to both SwimUniversity and the Master Spas winterizing procedure{:target=“_blank”}, this 30-minute flush removes biofilm from the plumbing lines before you drain.
You’ll often see grey or brown foam surface during the flush. That’s biofilm being purged from the lines, the exact material that would otherwise freeze inside your plumbing over winter. This step is consistently missing from competitor winterizing guides, and it’s the most important thing you can do for your plumbing.
Step 2: drain the spa completely
Turn off power at the breaker before draining, and keep it off for the remainder of the winterizing process. Open the drain spigot (typically at the base of the spa cabinet) or deploy a submersible pump. Direct the water away from your foundation; check local regulations on drain water disposal.
Drainage takes 1-4 hours depending on spa size. Residential spas typically hold 250-500 gallons. Reference our standard drain and refill guide if this is your first time using the drain spigot, the location and cap design vary by brand.
Step 3: remove and clean the filter
With the spa drained, pull the filter cartridge. Rinse thoroughly with a garden hose. If it’s been more than 30 days since the last cleaning, soak overnight in filter cleaner solution, allow 8+ hours for a full soak.
Let the filter dry completely, then store it indoors (a shed, garage, or closet works). Do not leave the filter in the spa shell over winter, moisture and freezing temps degrade the filter media.
EcoPur filter note: If your Master Spas spa uses an EcoPur Charge filter (the orange one), per manufacturer instructions, remove and discard it rather than storing it. EcoPur media filters are replaced every 6 months and cannot be stored after use.
Step 4: blow out the plumbing lines
Set your wet/dry shop vac to exhaust mode (blow, not suction) and insert the hose into each jet opening. Work through every jet systematically. Also blow out the drain fitting, air injector lines, and heater return lines.
Use the shop vac, not compressed air. The shop vac provides sustained airflow through the lines rather than short bursts. Sustained flow actually clears standing water; bursts push it around.
If there are lines you can’t fully access, use non-toxic propylene glycol spa antifreeze: pour down each jet opening to displace any remaining water. It’s safe to leave in lines and won’t harm plumbing or the spa shell.
Why this matters: Any water remaining in lines will freeze, expand, and can crack PVC fittings. That’s the repair bill we mentioned, $500-2,000+, depending on what breaks.
Step 5: remove remaining water from the shell
Use a large sponge or shop towels to soak up water pooled in the footwell corners and the equipment compartment. Dry the filter housing area completely. If you can tip the spa slightly, even a few degrees helps drain trapped water from low spots.
Step 6: clean the shell and cover
Wipe down acrylic or fiberglass surfaces with a spa surface cleaner. Pay attention to the waterline ring where body oils and calcium accumulate. Clean and condition the spa cover with a vinyl conditioner, cold temperatures crack unconditioned vinyl faster than UV exposure does.
Step 7: disconnect equipment and secure power
The breaker should already be off. Lock it out if you have a breaker lock, or tape over the panel to alert anyone working in the house. For above-ground installations in very cold climates, consider adding insulation around the equipment compartment.
Disconnect and bring inside any accessories: floating thermometers, aromatherapy dispensers, pillows. Foam pillows absorb water and will freeze-crack if left in.
Step 8: cover and secure for winter
Replace the spa cover and add locking cover clips or cables. Snow load can collapse or displace an unsecured cover. In exposed locations, decks, open yards, a windscreen adds meaningful protection against cover displacement in high winds.
According to the NSF spa maintenance guidelines{:target=“_blank”}, proper cover securing is one of the most overlooked aspects of seasonal spa closure.
Reopening your hot tub in spring
Spring reopening takes 2-4 hours plus water balance time. Here’s the order:
- Reinstall the filter cartridge (or install a new one if the old one was stored more than 6 months)
- Replace any drain plugs or fittings you removed
- Fill with fresh water using a pre-filter on the garden hose, this reduces mineral load significantly
- Add a sequestering agent to the fresh fill water
- Restore power; allow the system to circulate 30 minutes before testing chemistry
- Balance chemistry in order: total alkalinity first, then pH, then sanitizer
- Run a chlorine shock on the first fill to disinfect any biofilm that developed in standing equipment
Expect 4-6 hours to reach temperature from a cold fill. Check your chemistry again after the first full heat cycle, temperature affects pH and calcium readings.
If you’re also closing a swimming pool for the season, see our guide on winterizing a pool, the water chemistry closure steps differ from spa winterizing but the plumbing blowout logic is similar. For pool cover and storage tips, our pool cover guide covers winter cover weighting and pump setup.
FAQ
How long does it take to winterize a hot tub?
Expect 2-3 hours for the complete process: system flush (30 minutes), drainage (1-4 hours depending on spa size), and blowout and cleanup (30-60 minutes). If you’re doing an overnight filter soak, plan for that to run while the spa drains. The whole operation across two days, evening flush and drain, morning cleanup, is comfortable for most owners.
Do I need antifreeze in my hot tub lines?
Only if you can’t fully blow out all lines with a shop vac. If you’ve worked through every jet opening and the accessible line fittings, a thorough blowout is sufficient. Use non-toxic propylene glycol antifreeze for any lines you can’t reach, pour it into jet openings and let it sit. Never use automotive antifreeze (ethylene glycol). It’s toxic and will contaminate the spa surfaces.
Can I leave water in my hot tub over winter if it’s still running?
Yes, if the heater and circulation pump remain operational. A running spa maintains temperature and circulation that prevents freeze damage. The risk is an extended power outage during a hard freeze. If you’re in a region with ice storms or multi-day outages, have a winterizing plan as a backup. Monitor the spa remotely if possible.
What happens if my hot tub freezes?
Freeze damage cracks PVC plumbing, equipment housings, pump casings, and jets. Repairs typically run $500-2,000 depending on what breaks and how accessible the plumbing is. In severe cases where the heater or pump housing cracks, replacement costs exceed $2,000. Proper winterizing is always cheaper than freeze repair.
When should I winterize vs. wait?
Once nighttime temperatures consistently drop below 40°F and you’re not planning to use the spa for 4 or more weeks, winterize. The 40°F threshold gives you buffer, at that temperature, you have time to properly close the spa before freeze risk becomes imminent. Don’t wait until the night before a hard freeze.