A bathtub holds 40 to 60 gallons, and you only fill it to shoulder depth. Usable volume is often 35 to 45 gallons, which is roughly half a dedicated cold plunge tub.
Almost every chiller sold for cold plunging is rated for 79 gallons or more. On a bathtub that is oversized, and oversized chillers short cycle rather than run steadily, which is harder on the compressor than the work it was built for.
So this page is about matching, and about one prior question most buyers skip: whether a chiller makes sense on a bathtub at all.
We compared 9 units. We have not run them, and each pick says what we could not confirm.
The short answer
Every pick below wins one job. Find the line that sounds like you, then jump to the full write-up.
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Best Overall
Active Aqua 1/10 HP Water Chiller with Boost
A bathtub or a small tub you can leave filled, where you want hardware with a proven record rather than the cheapest option.
Check price on Amazon for Active Aqua 1/10 HP Water Chiller with Boost (opens in a new tab) Typically $300 to $800Read why it won for Active Aqua 1/10 HP Water Chiller with Boost -
Best With a Pump Included
BAOSHISHAN 1/3 HP Cold Plunge Chiller
A bathtub setup where you want the fewest separate parts and the least plumbing to work out yourself.
Check price on Amazon for BAOSHISHAN 1/3 HP Cold Plunge Chiller (opens in a new tab) Typically $300 to $800Read why it won for BAOSHISHAN 1/3 HP Cold Plunge Chiller -
Best Budget
EONIX 1/3 HP Cold Plunge Chiller
Someone starting in a bathtub who expects to buy a proper tub within a year and does not want to buy two chillers.
Check price on Amazon for EONIX 1/3 HP Cold Plunge Chiller (opens in a new tab) Typically Under $300Read why it won for EONIX 1/3 HP Cold Plunge Chiller
Compare them side by side
Same fields for every tub, so you are comparing like with like.
| Product | Award | Best for | Capacity | Material | Power source | Price | Where to buy |
|---|---|---|---|---|---|---|---|
| Active Aqua 1/10 HP Water Chiller with Boost | Best Overall | A bathtub or a small tub you can leave filled, where you want hardware with a proven record rather than the cheapest option. | 40 gallons | Plastic | Corded Electric | $$ $300 to $800 | Check price for Active Aqua 1/10 HP Water Chiller with Boost (opens in a new tab) |
| BAOSHISHAN 1/3 HP Cold Plunge Chiller | Best With a Pump Included | A bathtub setup where you want the fewest separate parts and the least plumbing to work out yourself. | 79 gallons | Stainless Steel | Corded Electric | $$ $300 to $800 | Check price for BAOSHISHAN 1/3 HP Cold Plunge Chiller (opens in a new tab) |
| EONIX 1/3 HP Cold Plunge Chiller | Best Budget | Someone starting in a bathtub who expects to buy a proper tub within a year and does not want to buy two chillers. | 79 gallons | Aluminum | Corded Electric | $ Under $300 | Check price for EONIX 1/3 HP Cold Plunge Chiller (opens in a new tab) |
The full reviews
Best Overall
Active Aqua 1/10 HP Water Chiller with Boost
Active Aqua AACH10HP
Rated for 40 gallons, which is genuinely the right size for a bathtub rather than a tub chiller pressed into service. Years of hydroponics history behind it, too.
What we like
- 40 gallon rating matches a bathtub's usable volume rather than overshooting it
- Long production history in hydroponics, so reliability is known rather than hoped
- Digital thermostat holds a set point instead of cycling roughly
- Fittings included, so plumbing hoses over a rim is straightforward
What we do not
- No pump included, so you buy one and match its flow rate
- 28 pounds sitting beside a bath is awkward in a small bathroom
- Costs about the same as chillers rated for twice the volume
Key specs
- Capacity
- 40 gallons
- Material
- Plastic
- Power source
- Corded Electric
- Price range
- $300 to $800
Most chillers sold for cold plunging are rated for 79 gallons or more. A bathtub holds roughly half that, so most of them are the wrong size.
Why 40 gallons is the right number
A standard bathtub holds 40 to 60 gallons filled to the overflow, and you only fill to shoulder depth when seated. Usable volume is often 35 to 45 gallons.
A 40 gallon rated chiller sits exactly on that. You are not paying for capacity you cannot use, and the unit will not spend its life short cycling on a small volume.
The history is the real argument
Active Aqua has been making reservoir chillers for hydroponic growers for years. That means the failure modes are documented, parts exist, and the reliability picture rests on long use rather than one busy season of cold plunge sales.
In a category where sellers appear and vanish, that matters more than a spec.
The pump problem
There is no pump in the box, and the flow rate has to suit the chiller.
Too little flow and the water in the heat exchanger gets too cold, the unit ices internally, and it short cycles. Too much and water passes through too quickly to lose meaningful heat, so the chiller runs constantly and never reaches your set point.
Neither looks like a pump fault. Both look like a broken chiller. Buy the pump the manufacturer specifies, not the one that was on offer.
Practical notes for a bathroom
28 pounds is manageable but it has to live somewhere, and bathrooms are short on floor space. Hoses run over the rim, which means you cannot close a shower screen and you should not leave them where someone trips.
Realistically this suits a spare or basement bathroom you can leave set up, or a garage tub. In a main bathroom that gets used for other things, the chiller becomes something you move twice a day, which defeats the point.
About the wattage
The listing says 1000 watts. That does not sit comfortably with a 1/10 HP rating, where you would expect far less.
One of those numbers is wrong and published information does not resolve it. Read the plate on the unit before you plan anything electrical.
Buy it if A bathtub or a small tub you can leave filled, where you want hardware with a proven record rather than the cheapest option.
Skip it if You plan to move to a 100 gallon dedicated tub soon, because this will then be undersized and you will buy twice.
The catch You have to buy a pump separately and match its flow rate to the chiller. Too little flow and the unit ices up internally; too much and the water passes through too fast to lose heat. Nothing on the box warns you, and both failures look like a broken chiller.
Not tested by us. Specs checked July 25, 2026. How we research
Best With a Pump Included
BAOSHISHAN 1/3 HP Cold Plunge Chiller
BAOSHISHAN ZQ-1002
1/3 HP with the pump and filter already inside, which removes the flow rate problem that catches most bathtub setups out. Rated to 42 degrees, colder than anyone needs.
What we like
- Pump and filter built in, so there is no flow rate to match and no second power lead
- One housing rather than a chiller plus a pump cluttering a bathroom
- Rated down to 42 degrees, well below the 50 to 59 most protocols use
- Runs from an ordinary socket with no electrical work
What we do not
- Modest review base, so long term reliability is not established
- No published wattage, so running cost is unknown before buying
- Oversized for a bathtub, so it will cycle rather than run steadily
Key specs
- Capacity
- 79 gallons
- Material
- Stainless Steel
- Power source
- Corded Electric
- Price range
- $300 to $800
The single most common way a bathtub chiller setup fails is the pump. This unit removes that failure by including one.
Why the built-in pump matters most here
A chiller needs water moving through it at a fairly specific rate. Buy separates and you have to match that yourself, and getting it wrong produces symptoms that look exactly like a faulty chiller: icing up, short cycling, or never reaching temperature.
With the pump and filter in one housing, that decision is already made. On a first setup that is worth more than a small difference in capacity or price.
It also means one object rather than three, which in a bathroom is not a trivial point.
The 42 degree claim
Ignore it, mostly.
Cold plunge protocols sit between 50 and 59 degrees Fahrenheit. Going colder does not obviously improve anything and it shortens how long you can safely stay in. A chiller rated to 42 is not better for you than one rated to 50; it just has more headroom on paper.
Where extra headroom does help is on a hot day with an uninsulated tub, because the unit is working further from its limit. That is a real if modest benefit.
Sizing against a bathtub
79 gallon rating on a 40 gallon bathtub means fast cooling and frequent cycling. Compressors prefer steady running to repeated starts, so the mismatch cuts both ways.
If the bathtub is permanent, a 40 gallon rated unit is the better engineering match. If you expect a dedicated tub within a year, this size is what you will want then.
What is not published
No wattage, so no way to estimate electricity. A modest review base, so no reliability record. Both are standard at this end of the market and both are worth knowing before you spend.
Buy it if A bathtub setup where you want the fewest separate parts and the least plumbing to work out yourself.
Skip it if You already own a suitable pump, because then you are paying for a component you do not need.
The catch Rating a chiller to 42 degrees sounds like an advantage and is mostly marketing. Nobody should be plunging below about 50, so the extra range is capability you will not use and should not pay a premium for.
Not tested by us. Specs checked July 25, 2026. How we research
Best Budget
EONIX 1/3 HP Cold Plunge Chiller
EONIX guanjie-10
A 1/3 HP unit rated to 79 gallons, which is more chiller than a bathtub needs. That oversizing is the point: it cools a warm bathtub fast, and it still fits a real tub later.
What we like
- Cheapest chiller here with a real gallon rating attached
- 79 gallon rating means it pulls a bathtub down quickly rather than slowly
- Still correctly sized if you upgrade to a 90 to 100 gallon tub later
- Runs from an ordinary household socket with no electrical work
What we do not
- Small review base with mixed ratings, so reliability is unproven
- No published wattage, so running cost cannot be estimated before buying
- Oversized for a bathtub, so it will short cycle rather than run steadily
Key specs
- Capacity
- 79 gallons
- Material
- Aluminum
- Power source
- Corded Electric
- Price range
- Under $300
The cheapest route to a chilled bathtub, and the reasoning for buying it is mostly about what you do next.
Deliberately too big
A bathtub needs about 40 gallons of cooling. This is rated for 79.
That mismatch has one real advantage: speed. Twice the rating means a warm bathtub comes down fast, which matters when the tub cannot stay filled and every session starts from tap temperature.
It has one real disadvantage, covered below.
The upgrade argument
Most people who start in a bathtub and stick with cold plunging buy a dedicated tub within a year. Those tubs are typically 85 to 105 gallons.
A 40 gallon chiller is then undersized and you buy again. A 79 gallon chiller is exactly right. So paying slightly more now for capacity you do not yet need can be the cheaper path overall.
That only holds if you actually upgrade. If the bathtub is your permanent setup, buy the smaller unit.
Short cycling is the cost
An oversized chiller reaches the set point, shuts off, warms slightly, and starts again. Repeat all day.
Compressors prefer long steady runs to frequent starts, because startup is where the wear happens. So the oversizing that gets you fast cooling is also working against the unit’s lifespan.
On a unit with no established reliability record, that is worth weighing.
What you cannot find out
No published wattage, so running cost is unknowable before purchase. A small review base with mixed rather than good ratings, so lifespan is unknowable too.
At this price that is the trade. Even two years of service would likely beat two years of bagged ice, which is the honest case for buying it.
Buy it if Someone starting in a bathtub who expects to buy a proper tub within a year and does not want to buy two chillers.
Skip it if You want a unit with a service record, because there is not enough owner history here to give you one.
The catch Oversized on a bathtub it will short cycle: reaching the set point quickly, switching off, then switching on again. Frequent cycling is harder on a compressor than steady running, so the mismatch that makes it fast also shortens its life.
Not tested by us. Specs checked July 25, 2026. How we research
Before you buy anything: does a chiller suit a bathtub?
This is the question the category skips, and for a lot of readers the answer is no.
A chiller earns its money by holding water cold between sessions so you never buy ice again. That requires the tub to stay filled.
A main bathroom does not stay filled. It gets used for showers and baths, and standing water is a hygiene problem, so you drain after every session. If every session starts from tap temperature anyway, a chiller is doing the hard job every single time and you have bought an expensive way to avoid ice.
A chiller makes sense on a bathtub when:
- It is a spare, basement or garage bathroom you can leave set up.
- The tub is outdoors or in a garage rather than a working bathroom.
- You are buying now for a dedicated tub you will get within a year.
It does not when:
- The bath is your only bath and gets used daily for other things.
If you are in the second group, use ice. Roughly 10 to 20 pounds does a bathtub, which is half what a dedicated tub needs. Our bathtub guide covers the numbers.
How we compared these
Nine chillers, then four tests.
Gallon rating against real bathtub volume. Not against the marketing figure for the bath, against the 35 to 45 gallons you actually fill.
Is a pump included? On a bathtub setup this is the most common point of failure, because matching a pump’s flow rate is not obvious and getting it wrong mimics a broken chiller.
Footprint. Bathrooms have no floor space. A 50 pound unit is a different proposition here than in a garden.
Would it still suit a dedicated tub? Most bathtub users upgrade. Buying twice is the avoidable cost.
The sizing tension, honestly
There is a real trade here and no single right answer.
A 40 gallon rated unit is the correct match. It runs steadily, which is what compressors prefer, and it costs less to run. It becomes undersized the moment you buy a 90 gallon tub.
A 79 gallon rated unit cools a bathtub fast, which matters when you refill every session. It short cycles, which is harder wear. It is exactly right after an upgrade.
Pick based on whether the bathtub is a stepping stone or the destination. That is genuinely the deciding factor, not the price difference.
Practical setup in a bathroom
Hoses over the rim is the standard arrangement and it works fine. Use the insulated hose if the unit ships with one, because an uninsulated run in a warm bathroom picks up heat and makes the chiller work harder for nothing.
Trip hazards. Wet tile, hoses across a floor, and someone cold and slightly disoriented getting out of a bath. Route the hoses where nobody walks and put a mat down.
Noise. These are compressors and a tiled bathroom is the most reflective room in the house. It will be louder than you expect.
Electrical. Every unit here runs from an ordinary socket. Bathroom sockets are a different matter: in many places they are restricted or absent for good reason. Do not run an extension lead into a wet room. If the only power is outside the bathroom, that is a signal the tub should be somewhere else.
Our final recommendation
If the bathtub is your permanent setup, buy the Active Aqua. It is the only unit here actually rated for a bathtub’s volume, it has years of production history behind it, and it will run steadily rather than cycling. Budget for a matched pump.
If you want the fewest parts and no flow rate to work out, the BAOSHISHAN has the pump and filter built in, which removes the most common failure in these setups. Ignore the 42 degree rating; you will never use it.
If you expect a dedicated tub within the year, buy the EONIX now. It is oversized for a bathtub and correctly sized for what you will own next, and buying one chiller instead of two is the larger saving. Accept that its reliability record does not exist yet.
How we researched this page
We compared 9 chillers on gallon rating against a bathtub's real usable volume, whether a pump is included, physical footprint in a bathroom, and whether the unit would still suit a dedicated tub after an upgrade.
What we worked from
- Manufacturer spec sheets
- Brand manuals and setup docs
- Verified owner reports
- Warranty terms
- Retailer listing data
- Price history
9 units were compared before these 3 made the page.
What we handled ourselves
None of the products on this page. Nobody can buy every tub on the market and we are not going to pretend otherwise.
What we could not confirm, product by product
- Active Aqua 1/10 HP Water Chiller with Boost
- The listing states 1000 watts against a 1/10 HP rating, which does not add up. We could not resolve which figure is correct, so treat the power draw as unconfirmed and read the rating plate before planning any wiring.
- BAOSHISHAN 1/3 HP Cold Plunge Chiller
- No published wattage and a modest review base. We could not confirm the pump's flow rate, which matters if you ever want to run the unit on a larger tub.
- EONIX 1/3 HP Cold Plunge Chiller
- Too few owner reports to judge reliability, and the small sample skews mixed rather than positive. No published wattage, so we cannot compare running cost.
Questions people ask before they buy
What size chiller do I need for a bathtub?
A bathtub's usable volume is around 35 to 45 gallons, so a 40 gallon rated unit is the correct engineering match. A 79 gallon unit will work and will cool faster, but it cycles rather than running steadily.
Does a chiller actually make sense on a bathtub?
Only if you can leave the tub filled. A chiller earns its money by holding water cold between sessions. A main bathroom that gets used for other things means you drain after every session, which is exactly the situation a chiller does not help.
Do I need a separate pump?
If the chiller does not include one, yes, and its flow rate has to suit the chiller. Too little and the unit ices up; too much and the water passes through too fast to cool. Both look like a broken chiller. Prefer a unit with the pump built in.
Will hoses over the bath rim work?
Yes, that is the normal arrangement, and it is why bathtub setups are simple. Keep the hoses where nobody will trip and expect not to be able to close a shower screen.
Should I buy for the bathtub or for a future tub?
If you expect a dedicated 90 to 105 gallon tub within a year, buy the 79 gallon rated unit now and accept some cycling. If the bathtub is your permanent setup, the 40 gallon unit is the better match and cheaper to run.
How cold will it get a bathtub?
Well below what you need. Every unit here reaches the low 40s, and cold plunge protocols sit at 50 to 59 degrees. Temperature range is not the limiting factor; volume and cycling are.
Why you can trust this page
- Who wrote it
- Jed Callahan, Editor, Cold Plunge Daddy
- When
- Published July 25, 2026, updated July 25, 2026
- How we picked
- We compared 9 chillers on gallon rating against a bathtub's real usable volume, whether a pump is included, physical footprint in a bathroom, and whether the unit would still suit a dedicated tub after an upgrade.
- What we looked at
- 3 products made this page after the cut.
- How we make money
- Amazon pays us a small commission when you buy through our links. Nobody pays us for a good review and no brand sees a page before it goes live.
- What we do not do
- We do not run these tubs ourselves, so we never claim we did. Every pick here comes from spec sheets, manuals, warranty terms and owner reports, and each review says what we could not check.
Written by
Jed Callahan
Editor, Cold Plunge Daddy
I have spent more nights than I want to admit doing math on ice bath listings to find out whether the gallon number is a lie. It usually is. I have been in some of this gear and not all of it, and I always tell you which. I am not a doctor, and I am not going to pretend cold water fixed my life.
- Catching bad spec sheets
- Chiller sizing and power draw
- Warranty and return terms
- What a tub costs to run