How to Winterize Your Sauna and Cold Plunge
Share
As the leaves fall and the air turns crisp, it’s the perfect time to prepare your sauna and cold plunge for winter. If you live in a region where temperatures dip significantly, a little preparation goes a long way. Winterizing protects your investment, extends the life of your equipment, and ensures you can keep your wellness routine steady all season long. To help, we’ve put together a simple checklist to guide you through the process.
First, we’ll walk you through seasonal maintenance and tips for your Redwood Outdoors sauna. Then we’ll run down how to care for and prepare your cold plunge for cooler weather.
Key Takeaways
- Cold plunge systems must not be operated, stored, or left filled with water in temperatures at or below 32°F (0°C).
- Damage caused by use in temperatures below 32°F is not covered by the warranty.
- Chlorine/bromine tabs are not required to keep the water sanitary in an All-In-One system. Adding chlorine/bromine can corrode the equipment, and that corrosion is not covered under Redwood Outdoors’ product warranty.
- Clean your filter monthly, not every three months, and change the water monthly.
- When winterizing, leave the primary drain open for one hour before opening the winterization drain.
Cold Plunge Care and Winterizing at a Glance
| Task | How often |
|---|---|
| Rinse off before entering | Every session |
| Test the water | Weekly, after every water change, and more often with heavy use or multiple users |
| Run filter cycles (Wi-Fi models) | At least 4 hours daily |
| Clean the filter | Monthly — more often for high-use settings like spas or gyms |
| Change the water | Monthly |
| Replace the filter | Annually, or sooner if the paper filter is discolored, bent or degraded |
| Winterize | Once temperatures drop below 32°F |
How Do You Winterize Your Sauna?
It’s sauna season! Your Redwood Outdoors sauna is built for year-round use, but many of our customers find themselves enjoying it most during the cooler months. Sauna sessions offer a cozy way to warm up while supporting heart health by improving circulation and easing blood pressure. [1] [2] If you’re new to pairing the two, our guide to hot and cold therapy covers how a contrast routine works.
Before the weather turns, you’ll want to check on your exterior and, if you have a WiFi heater, your electrical junction boxes. As the seasons change, explore our tips for keeping your sauna performing at its best.
Protecting the Exterior
- If you’ve decided to stain or seal the exterior of your sauna, fall may be a good time to reapply if needed, so you maximize the benefit of the product.
- Inspect your roof before the snow flies. Make sure your shingles are secured and check for any damage.
Electrical & Heater Considerations
- Make sure the weatherproof boxes for your WiFi heater components (if applicable) are sealed properly.
- If you have a Harvia KIP heater, now is a great time to pull out all of your rocks and assess the situation so you can purchase a fresh box of rocks if needed. Make sure you have lots of large rocks on hand to replace broken chunks inside the heater for the next few months. Higher usage during colder weather means you’ll need to attend to rock replacement more often.
Performance in Cold Weather
- Heat-up times will naturally be a bit slower due to lower ambient temperatures, so your pace of pre-heating might shift. Pay attention to your heat-up times as the weather shifts so you can update your pre-heating schedule as needed.
- You might play around with keeping your vent holes closed more often to fine-tune your interior temperature and air circulation in colder temps.
Above all, make time to enjoy your sauna this winter! It’s the perfect retreat from chilly days, giving you a moment to relax, recharge, and build resilience so you can show up fully for yourself and your loved ones during the busy season.
If you find you’re not using it as often, running the heater for 30–60 minutes once or twice a week will help prevent moisture buildup. And if you’ll be away for the holidays, placing trays of desiccants or a small dehumidifier inside can keep your sauna fresh and ready for your return.
How Do You Keep Your Cold Plunge Water Clean?
Good water habits protect the tub, the filter and the chiller components — and they matter more in winter, when the plunge sees heavier use. This guidance applies to both the Alaskan All-In-One and the Denali All-In-One.
Rinse before you get in. Always rinse off before entering the cold plunge. This reduces grass, debris and other contaminants entering the tub, filter and chiller components. It’s the single easiest thing you can do to extend the life of your equipment.
Skip the chlorine and bromine. Chlorine/bromine tabs are not required to keep the water sanitary in an All-In-One system — the UV sanitizer and filtration handle it. Adding chlorine/bromine can corrode the equipment, and corrosion caused by chlorine/bromine is not covered under Redwood Outdoors’ product warranty. Any damage due to improper water chemistry isn’t covered either.
If your setting requires bromine — some commercial spa environments do — talk to our team before you buy, because an All-In-One system may not be the right fit.
Test your water weekly. Test at least once a week, after every water change, and more often when the plunge gets heavy use or has multiple users. Regular testing keeps water quality stable and reduces mineral deposits and other conditions that can damage equipment.
Filter cycles and UV on Wi-Fi models
If you have a Wi-Fi model, schedule at least four hours of filter cycles daily. A filter cycle runs the water pump and UV light for the scheduled period, and you can set it as one continuous block or two shorter ones.
Set the 002 Series disinfection mode to Auto so the UV light runs whenever the pump operates. Filter-cycle settings override Manual UV behavior during scheduled cycles.
Filters and water changes
Clean your filter monthly, not every three months. High-use locations like spas or gyms need it more often. A filter cartridge typically lasts 6 to 12 months, but only if it’s cleaned regularly — and replace yours sooner if the paper filter is discolored, bent, degraded or otherwise deteriorated.
To clean a cartridge, remove it from the housing, place it in a bucket of water with a filter cleaning agent, and swish to mix. Once it’s fully dried out, it can go back in. We recommend buying filter cartridges in pairs so you can rotate — that way you don’t have to stop using your plunge while one is being cleaned.
Change the water monthly. The Denali holds 80 gallons and the Alaskan holds 104. On the Alaskan, draining the tub is necessary to remove and service the filter — so do both at the same time and save yourself a step.
How Do You Winterize an All-In-One Cold Plunge?
Your Denali or Alaskan All-In-One Cold Plunge is designed to be left outdoors year-round, only if the following precautions are adhered to.
Cold plunge systems contain water-filled internal components that can be damaged if exposed to freezing temperatures. They must not be operated, stored, or left filled with water in temperatures at or below 32°F (0°C). If used below freezing, ice will form on the internal components and damage the equipment.
Below 32°F, the tub must be drained and winterized as per the instructions in the user manual. Damage caused by use in temperatures below 32°F is not covered by the warranty.
Once temperatures drop below 32°F, you’ll want to initiate the winterization process.
Steps for winterizing:
- Open the air lock and remove the filter canister lid
- Remove the filter from the canister
- Leave the system open so water has room to expand if any remains
- Open the primary drain and leave it open for one hour to remove as much water as possible
- Then open the winterization drain, which connects directly to the chiller. Opening it before the hour is up can send water across a wide area
- Clean the filter, let it fully dry, and store it indoors
Leave both the primary and winterization drains open for the entire storage period.
You should not use the unit at all while winterized. Once temperatures stay consistently above safe temperature thresholds for the All-In-One systems, you may set your tub back up and get back to plunging!
Please consult your product manual for full step-by-step instructions on winterization. If you cannot find your manual, reach out to us at support@redwoodoutdoors.com, and we’d be happy to resend it.
What About Older Tubs With a Standalone Chiller?
If you own a Pacific or Yukon Cold Plunge, or an Alaskan tub paired with a separate chiller unit, the process is different. These systems are no longer part of the current lineup, but the guidance below still applies.
First, identify whether you have the Standard or Deluxe Chiller. This designation would be reflected on your order invoice or by checking the product tag on the back of the unit.
- Model: CHL-SD will be a Standard Chiller
- Model: CHL-DX will be a Deluxe Chiller
If you purchased a Pacific Cold Plunge tub from us, you have the Deluxe Chiller.
When to bring the chiller inside:
| Chiller | Bring inside at |
|---|---|
| Standard Chiller (CHL-SD) | Anything below 35°F |
| Deluxe Chiller (CHL-DX) | Anything below 5°F — start acting when temps hit ~10°F. Below 5°F the chiller’s lubricating oil can freeze and seize the machine |
Steps for winterizing:
- Drain the tub completely
- Remove your hoses and drain completely
- Remove and empty the filter compartments from the Chiller
- Tip the chiller on its side to fully drain
- Remove and clean all filters, let them fully dry, then store indoors
- Move chiller inside (garage, shed, or home)
Unlike the All-In-One systems, standalone chillers are designed to be used with bromine as a sanitizer. The water balancing kit matters here too — out-of-balance water will damage chiller equipment, and that damage isn’t covered under warranty.
If you still want to use your tub during the winter, you’ll want to keep the hoses disconnected and replace them with the cap fittings. It’s also important to swish the water regularly to prevent a complete freeze-over.
Once temperatures stay consistently above safe temperature thresholds for your chiller, you may bring your chiller back outside and connect it to your tub.
Please consult your product manual for full step-by-step instructions on winterization. If you cannot find your manual, reach out to us at support@redwoodoutdoors.com, and we’d be happy to resend it.
FAQs
Can you leave a cold plunge outside in winter?
Your Denali or Alaskan All-In-One Cold Plunge is designed to be left outdoors year-round, only if the following precautions are adhered to. The minimum operating temperature for our All-In-One plunge tub systems is 32°F. Below 32°F, the tub must be drained and winterized as per the instructions in the user manual.
Can you put chlorine or bromine in an All-In-One cold plunge?
Chlorine/bromine tabs are not required to keep the water sanitary in an All-In-One system. Adding chlorine/bromine can corrode the equipment, and corrosion caused by chlorine/bromine is not covered under Redwood Outdoors’ product warranty.
How often should you clean a cold plunge filter?
Clean your filter monthly, and more often in high-use settings like spas or gyms. Filters are on an annual replacement schedule, but replace yours sooner if the paper filter is discolored, bent or degraded. Change your water monthly as well.
What happens if you run a cold plunge below freezing?
If used in temperatures below 32°F, ice will form on the internal components and damage the equipment. Damage caused by use in temperatures below 32°F is not covered by the warranty.
How long should filter cycles run on a Wi-Fi model?
Schedule at least four hours of filter cycles daily. A filter cycle runs the water pump and UV light for the scheduled period, set as one continuous block or two shorter ones. Set disinfection mode to Auto so UV runs whenever the pump does.
What if I’m not using my sauna much over winter?
Running the heater for 30–60 minutes once or twice a week will help prevent moisture buildup. If you’ll be away for the holidays, placing trays of desiccants or a small dehumidifier inside can keep your sauna fresh and ready for your return.
Make sure to bookmark this page so you can come back to it when you need it. With a few simple steps to winterize your sauna and cold plunge, you can keep your wellness routine going strong all season long. A little preparation now means uninterrupted hot and cold therapy through the winter - so get ready, stay consistent, and enjoy every moment.
Ready to build out your setup? Browse our saunas, cold plunges, and Fire & Ice bundles.
Sources
- Laukkanen JA, Laukkanen T. Sauna bathing and systemic inflammation. European Journal of Epidemiology, 2018. https://pubmed.ncbi.nlm.nih.gov/29351426/
- Sauna bathing, cardiovascular function and blood pressure. PMC, 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8285605/