Hot Tub Materials Compared
The best hot tub material depends on how you will use the tub. Acrylic is the most forgiving on water care, traditional cedar is the most natural, rotomolded plastic is the lowest cost, stainless steel tolerates chlorine, and cedar-clad aluminum can sit empty, moves easily and takes almost any water as a fill. Here are the tradeoffs of each, and the questions worth putting to any maker.
Most hot tub material comparisons are written by someone who sells one of the materials. This one is too, so read it with that in mind. We've tried to state the tradeoffs we'd want stated if we were the ones buying, and every material here suits someone.
Acrylic over fiberglass
The mainstream option. Molded acrylic, insulated cabinet, jets.
Strengths: forgiving on water chemistry, since the acrylic is chemically inert. Comfortable molded seating and jets for anyone who wants hydrotherapy. Widely serviced. Chlorine and salt systems work fine.
Tradeoffs: the tub is molded acrylic, a petroleum-based plastic, which matters to some buyers more than others. Heavy, typically 700 to 1,000 lbs empty, so it usually stays where it is first sited. The working parts sit behind panels and foam insulation, which can make them harder to reach. Jets and internal plumbing runs give water places to sit between soaks, which is why many acrylic spas are sold with UV or ozone to bring sanitizer demand back down. Cabinet and frame are the usual wear point rather than the acrylic itself, and disposal at the end of its life takes planning, since the materials are rarely recyclable.
Traditional all cedar
The classic. Staves held with steel bands, sealed by the wood swelling.
Strengths: beautiful, natural, no synthetic material against the water. Repairable stave by stave.
Tradeoffs: it is sensitive to water exposure in both directions. The seal exists because the wood is swollen, so the tub generally has to stay filled. Let it dry out and the staves contract, and it can leak or crack when it swells again. That makes it less suited to a seasonal cabin, a rental with gaps between bookings, or anywhere with a hard freeze.
It usually arrives as a kit rather than a tub, so it is assembled on site, and once assembled and swollen it is effectively fixed in place. Moving it means taking it apart.
Wood in constant contact with warm water wears with time, so it asks for more attention over the years. Cedar is porous, so it is harder to keep clean and sanitize than a smooth surface. The steel bands need watching too. And there is usually no insulation in the walls, so heat loss is higher and heat up times are longer, particularly in cold weather.
Rotomolded plastic
The value end. Single piece polyethylene.
Strengths: the lowest upfront cost, light, and very durable in normal use.
Tradeoffs: a simpler, more utilitarian look. A limited lifespan in strong sunlight unless it is kept covered, and generally not repairable or recyclable in most municipalities. Inflatable tubs sit at the same end of the market, and inflatable vs cedar hot tubs compares what you get for the money.
Stainless steel
The other metal. A welded stainless vessel, usually clad in wood.
Strengths: durable, smooth and non-porous like aluminum, and it tolerates chlorine: in pool immersion testing, 304 and 316 stainless showed insignificant general corrosion even under unusually high chlorination. That matters most where chlorine is required, in a commercial or regulated setting run by rotating staff, and it is the clearest case for a stainless tub. For a private owner it matters less, since nobody wants more sanitizer than they need, and an aluminum tub runs on less of it.
Tradeoffs: it is not chemistry-proof. Stainless protects itself with the same kind of oxide film aluminum does and stays sound within its limits; outside them, in chloride-rich water, it can pit at welds and under fittings, and it needs proper weld finishing to hold its corrosion resistance. Ordinary 304 and 316 grades do not take sea water, where a marine-grade aluminum tub is filled from the ocean, changed every five to seven days and rinsed between. It is roughly three times the density of aluminum, so a stainless tub is heavy to move and usually stays where it is put. It conducts heat less well. And it is welded, where an aluminum tub is riveted like an aircraft, a boat hull or an Airstream, which keeps the full strength of the alloy at every joint and lets a rivet be replaced by hand decades later. Neither metal is superior; they suit different products. Aluminum vs stainless steel hot tubs goes through it question by question.
Cedar-clad aluminum
What we build. A riveted 5052 marine-grade aluminum structure with a cedar exterior, made on the Sunshine Coast since 2001.
Strengths: the water sits against smooth aluminum, not plastic or porous wood. It doesn't rely on swelling to stay watertight, so it can be left empty over a winter or between bookings without leaking or cracking, and it isn't climate sensitive. It doesn't crack or delaminate the way molded materials can.
It arrives pre assembled rather than as a kit, and it's built with 360 degrees of insulation, so heat goes into the water and stays there. Light enough to move at 200 lbs empty for the Small, 220 for the Standard and 300 for the Large, so it can go where a heavier spa can't easily follow, and it stays moveable afterwards.
Nothing is buried. The cedar, the firebox, the heater, pump, board and filtration are all bolted, banded or slotted onto the aluminum structure, so any of them can be reached and replaced by hand. The heating system can be changed as your property and plans change, and a Hybrid runs wood, electric or both. We still supply parts for tubs built two decades ago, which is what a 25 year structural warranty actually rests on.
No UV or ozone required. Many spas are sold with UV or ozone, and on those designs it does a real job: it reduces how much sanitizer the spa needs where jets, internal plumbing and packed foam give water places to sit. An AlumiTub doesn't need one. Water sits in a smooth aluminum vessel with a simple filter circuit, and everything it touches can be reached and cleaned by hand. Keep the water in range and sanitizer demand stays low on its own. One less thing in the circuit, and one less thing to replace.
Tradeoffs, stated plainly: aluminum is a metal, and several sanitizers that are standard for acrylic spas aren't compatible. No chlorine, no salt systems, no copper or silver products. Bromine and plant derived treatments are what work, and calcium hardness needs to sit in a defined range. Kept within those, the aluminum stays sound for decades; the compatibility list is there to keep the wrong products out, not because the metal is fragile. A stainless tub would tolerate a chlorine tablet that an aluminum tub does not, which matters where chlorine is required; the trade is weight, heat transfer and sea water fills.
That's less of an obstacle than it sounds, because we don't leave owners to work it out. Good Clean Living Water Care is a curated collection built specifically around aluminum and around our published ranges: fill purification, balancers, a monthly plant derived stabilizer, filter care, and a deep clean every 3 to 4 months. Everything in it is compatible by design, so water care is a routine rather than a research project.
What protects the aluminum is the metal itself. Aluminum forms a thin oxide layer that re-forms continuously, which is why it lasts for decades on boat hulls and aircraft, and everyday water care keeps it that way. On Electric, Hybrid and Wood Fired with Filtration tubs, three magnesium anodes add a layer of protection. Do aluminum hot tubs corrode? has the short answer, and how the aluminum is protected has the detail.
Questions to ask any maker
Buyers often arrive comparing the figures each maker chose to publish, which rarely line up. These questions work the other way: put the same ones to every maker, us included, and compare like for like. Here are our answers.
| Question | AlumiTubs | Other makers |
|---|---|---|
| How deep is the water over the seat at the recommended fill? | 21.5 in over a 13.5 in bench on the standard 38 in build, or 24.5 in filled to the brim. On a 44 in build, 27.5 in, or 23.5 in on a raised 17.5 in bench. On a 48 in build (Electric only), 31.5 in, or 25.5 in on a raised 19.5 in bench. | Ask them |
| How much water is there per seat? | Small 315 US gal (1,192 L), Standard 420 US gal (1,590 L), Large 650 US gal (2,461 L). Wood Fired and Hybrid seat 2, 5 and 8: about 158 gal (596 L), 84 gal (318 L) and 81 gal (308 L) per seat. Electric seats 4, 7 and 10: about 79 gal (298 L), 60 gal (227 L) and 65 gal (246 L) per seat. | Ask them |
| What does it weigh empty? | 200 lbs Small, 220 lbs Standard, 300 lbs Large. | Ask them |
| What does the base price include? | 360 degrees of insulation in the walls, a floating insulation layer on the water and a drain valve as standard. The lid is sold separately, and the rigid insulation under the base is part of your site prep. | Ask them |
| How long from delivery to first soak? | About an hour on a prepared site, plus an electrician for Electric and Hybrid. | Ask them |
| What does the warranty cover, and for how long? | A 25 year structural warranty, covering leaks and structural failure. | Ask them |
| Can the heating system be changed later? | Yes. The heating system is modular: a Wood Fired built with the compatibility ports can take electric heating and filtration later, and a Hybrid runs wood, electric or both. | Ask them |
Sizes and seating for each system are set out in hot tub dimensions and sizes.
Choosing
| If you want | Look at |
|---|---|
| The widest choice of sanitizers, molded seating and jets | Acrylic |
| A natural all-wood tub that will stay filled year round | Traditional cedar |
| The lowest upfront cost in a light, durable tub | Rotomolded |
| A commercial tub that must run on chlorine | Stainless steel |
| 360 degrees of insulation, flexible heating options, portability, sea water fills and replaceable components | Cedar-clad aluminum |
If you want a straight answer about whether an aluminum tub suits your water and your property, email hi@alumitubs.com with your location and water source. We'd rather talk someone out of the wrong build than sell the wrong one.
Go deeper: wooden hot tubs: what to know before you buy and how to choose a hot tub.
Common questions
What is the best material for a hot tub?
It depends on what you value. Acrylic is the most forgiving on water chemistry and offers molded seating and jets, but it is heavy, usually stays where it is first sited and is hard to recycle. Traditional all cedar is beautiful, but the seal depends on the wood staying swollen, so it generally has to stay filled, it arrives as a kit to assemble on site and the walls are uninsulated. Rotomolded plastic is the lowest cost and very durable, with a limited lifespan in strong sunlight. Stainless steel tolerates chlorine, which matters where chlorine is required, and is about three times the weight of aluminum. Cedar-clad aluminum stays watertight when left empty, arrives pre assembled with 360 degrees of insulation, offers wood fired, electric or hybrid heating that can be changed later and takes sea water fills, but needs a compatible sanitizer and calcium hardness within a defined range.
What should I compare when choosing a hot tub material?
Compare the same figures from every maker, rather than the ones each chooses to publish: water over the seat at the recommended fill, water per seat, empty weight, what the base price includes, setup time, what the warranty covers and for how long, and whether the heating system can be changed later. The questions to ask any maker table on this page gives AlumiTubs' own answer to each.
Why do hot tubs need UV or ozone, and does an aluminum hot tub need it?
UV and ozone exist to reduce how much sanitizer a spa needs. They are common on acrylic spas because multiple jets, long internal plumbing runs and packed foam give water places to sit between soaks, where biofilm forms and sanitizer demand climbs. In an AlumiTub the water sits in a smooth aluminum vessel with a simple filter circuit, and everything it touches can be reached and cleaned by hand, so demand stays low on its own once the water is in range. UV also breaks bromine down as water passes through it, and bromine is what an aluminum interior requires, so the two work against each other.
Is an aluminum hot tub better than a traditional cedar hot tub?
A cedar-clad aluminum tub does not rely on the wood swelling to stay watertight, so it can be left empty over a winter or between bookings without leaking or cracking, and the cedar is not in permanent contact with warm water. It also arrives pre assembled rather than as a kit, is insulated through 360 degrees, and stays moveable. The tradeoff is that aluminum is a metal, so chlorine, salt chlorine generators and copper or silver based products are not compatible, and calcium hardness needs to sit between 150 and 250 ppm.
Is stainless steel better than aluminum for a hot tub?
No. Both protect themselves with a self-repairing oxide film, and in a tub kept within its water care ranges neither corrodes or pits. Stainless tolerates chlorine, which matters only where chlorine is required in a commercial setting. Aluminum is a third the weight, conducts heat far better, is riveted like an aircraft or a boat hull rather than welded, and takes sea water as a fill, which ordinary stainless does not. For a tub people move themselves and fill from whatever water is nearby, aluminum's properties fit.
How much does an aluminum hot tub weigh?
Empty weights are 200 lbs for the Small, 220 lbs for the Standard and 300 lbs for the Large, compared with 700 to 1,000 lbs for a typical acrylic spa. That is light enough to roll into place by hand and light enough to move with you.