Cold Weather Testing: How to Winterize Your Wood Fire Hot Tub
An AlumiTub can be used all winter, even in extreme cold. Canadian winters are not for the faint of heart, and for many owners winter is when the tub gets used most. Snow falling, steam rising, quiet nights under the stars. It is hard to imagine a better way to warm up.
A note on winter and materials
When people ask about using a wood fired hot tub in winter, they are usually picturing a traditional cedar tub. Cold, moisture and freezing are hard on wood over time, and those concerns are valid.
AlumiTubs are built differently: aluminum-lined, fully insulated, and designed to be used and cared for in real winter conditions. Everything below reflects how they behave in cold climates, based on years of use across Canada and the northern US.
Can you use one in winter?
Yes. However cold it is where you live, an AlumiTub will reach 104°F, or whatever your soaking temperature is, just as an electric tub would. We are asked about Calgary, Winnipeg, northern British Columbia and the northeastern US, and the answer is the same each time.
The difference from an electric tub is that there is no button. Heating a wood fired tub is an active process, and winter asks you to be a little more intentional. For many people that is the appeal rather than the drawback.
How they perform in extreme cold
Cold affects how long heating takes. It does not prevent winter use.
AlumiTubs are insulated in three layers, 3.5 inches of rigid board beneath the base, 360 degrees around the tub and a floating layer on the water surface, and heat through a fully submerged firebox. Together those let the tub heat efficiently and hold heat for days on surprisingly little wood. Overnight loss with the lid in place is roughly two to three degrees Fahrenheit.
Three variables shape winter performance:
- Fill water temperature. Colder source water takes longer. If your property allows a warmer fill, that cuts heat-up time considerably. At an off-grid property, cold water is entirely manageable, it just takes longer.
- Outside temperature. Insulation matters more the colder it gets. Insulating beneath the tub and around the foundation, and keeping the floating insulation beneath the lid while heating and between soaks, improves retention and cuts the wood needed.
- Wood quality. Dry, well seasoned wood is essential in winter. It burns hotter, smokes less and transfers heat more efficiently. Many owners prepare their winter supply well in advance.
We regularly see AlumiTubs used at minus forty and below, with consistent results. On the wood fired side they have been tested heating in ambient conditions as cold as minus forty-four degrees Celsius.
Even kept it burning through the minus 30°C nights of Alberta winters.
Mitch and Sherry Metrunec, owners since 2016
What actually causes damage
Two things can damage an AlumiTub in winter, and both are entirely preventable.
Lighting the fire without enough water in the tub. Everyone at your property should understand this one. Fill to the line marked on the tub, or at least 4 inches above the chimney collar, and keep the water there the entire time the firebox is hot. Firing below that line warps the firebox, creates a safety risk, and voids firebox coverage.
Letting the tub or its drain kit freeze while holding standing water.
Freezing is not about winter itself. It is about water being left where it should not be. As long as the water is either held above freezing through use, or fully drained when not in use, freeze damage is easy to avoid.
Using it through winter, or shutting it down
The right approach depends on how often you will use it.
If you are soaking regularly, keep the tub in use. Regular heating holds the water above freezing and removes the need for draining. With good insulation and a well fitting lid, many people run theirs all winter without issue.
On a grid-connected property with no risk of power loss, some owners add a water de-icer or trough heater for peace of mind through the coldest stretches.
If the tub will sit unused, especially at a property you visit rarely, a winter shutdown is the better option. That means draining completely and making sure no standing water remains. Never drain until the firebox has fully cooled.
We don't have running water in the winter so we fill it from the lake with a gas powered pump, and best of all when we're done for the weekend all that's required is to drain the water and cover. No plumbing to pump antifreeze into. So simple and easy.
Ryan Coleman
On Electric and Hybrid models there is a third option: freeze protection heats the water automatically whenever the system detects cold, for as long as there is power, which is what makes leaving an unattended property through winter workable without draining every time. Plan for a long outage separately, since that protection depends on the supply. On a Hybrid the firebox covers exactly that gap.
All three approaches are valid. What matters is choosing one and being consistent.
How to winterize an AlumiTub
Winterizing is only necessary if the tub will not be used through freezing conditions.
Because the interior is aluminum, it is straightforward. Once the firebox is fully cool, drain it, wipe it dry, and cover it completely. Some owners remove the chimney and use the firebox cover plate and cedar lid to protect all the components.
If your tub has a drain kit, open the valve so no standing water remains in the PVC. With a snap drain there is no plumbing to freeze.
Being able to fully drain and dry the tub is one of the key differences from a traditional cedar design, which relies on staying filled.
Why aluminum behaves differently in winter
A traditional cedar tub relies on wood to both hold water and provide structure. Moisture absorbed into the wood freezes and expands, which leads to leaks, rot and a shorter life.
A marine-grade aluminum interior does not absorb water. The tub can be fully dried when needed, which removes the freeze expansion problem entirely. It also improves heat retention and reduces long-term maintenance in cold climates, and it is why the structure carries a 25 year structural warranty.
For many owners that difference is what makes year-round use realistic rather than stressful.
Owners in winter
Kevin MacLean turned a feed shed into a hot tub shack in northern BC:
I ordered a tub from you five years ago with the idea of turning this feed shed into a hot tub shack. 8 track player, velvet paintings, movies and darts. It worked out better than I thought. I live in northern BC and wanted to use it year round. And do. Even works at -40.
Kevin MacLean, northern BC
I bought our hot tub from AlumiTubs about five years ago for the guest house I rent out. It has worked great. It's easy to clean for new guests, and I can also leave it empty in winter without damaging it like a wooden hot tub. I leave a little booklet in the house that explains how it works and sometimes I show them. They love it.
Leo Downey, Rocky Mountain Buffalo Ranch and Cabins, British Columbia
Leo's full account is here.
Frequently asked questions
Can you use a wood fired hot tub in freezing weather?
Yes. An AlumiTub reaches 104F however cold it is outside, and on the wood fired side has been tested heating in ambient conditions as cold as minus forty-four degrees Celsius. Cold affects how long heating takes rather than whether it works. The three things that matter are fill water temperature, outside temperature, and how dry your wood is. Three layers of insulation and the lid hold overnight loss to roughly two to three degrees Fahrenheit.
What causes freeze damage to a hot tub?
Water left standing where it should not be, either in the tub or in the drain kit. Freezing is not about winter itself. As long as water is held above freezing through regular use, or fully drained when the tub is not in use, freeze damage is avoidable. The other risk in winter is lighting the fire before the tub is filled to the line, or at least 4 inches above the chimney collar, which warps the firebox and voids firebox coverage.
Should I drain my hot tub for winter or keep using it?
If you soak regularly, keep it in use, since regular heating holds the water above freezing. If the property sits unused for long stretches, drain it completely once the firebox has fully cooled. On Electric and Hybrid models there is a third option: freeze protection heats the water automatically whenever cold is detected, for as long as there is power, which makes leaving an unattended property workable without draining every time. Plan for a long outage separately, since that protection depends on the supply.
How do you winterize a wood fired hot tub?
Only necessary if the tub will not be used through freezing conditions. Once the firebox has fully cooled, drain it completely, wipe it dry and cover it. If it has a drain kit, leave the valve open so no standing water remains in the PVC. With a snap drain there is no plumbing to freeze. An aluminum interior can be fully dried and left empty, which a traditional cedar tub cannot, because that design relies on staying filled.