A cold tub is any vessel you sit in to get cold water around your body, and the word covers a much wider price range than most buyers expect. At one end it is an uninsulated tub you fill with a hose and a bag of ice; at the other it is an insulated shell with a chiller, a pump and a filter that holds a set temperature all year. Knowing which of those you are shopping for is the first decision, because everything else follows from it.
The three kinds of cold tub
The cheapest cold tub is a plain vessel: a stock tank, a barrel or a molded shell with no insulation and no cooling. You fill it and add ice, and the water warms back up over a day or two. The middle tier adds insulation and a cover, which slows that warming and cuts how much ice you buy. The top tier adds a chiller, which is a refrigeration unit that holds the water at a temperature you set, plus a pump and usually a filter so the same water stays usable for weeks. The jump in price between the middle and top tiers is the largest in the category, and it buys convenience rather than a colder minimum.
What the running cost actually is
A plain tub has no running cost beyond water and ice, and the ice is the part that surprises people: keeping an uninsulated tub genuinely cold through a warm week can mean buying bags several times a week, which adds up faster than the equipment gap suggests. An insulated tub with a cover cuts that sharply. A chilled unit removes the ice entirely and replaces it with electricity and filter media, and it needs an outdoor outlet within reach. Whichever tier you choose, the water still needs changing or treating, because a tub you sit in repeatedly is a tub that needs sanitation.
Sizing and siting before you buy
A cold tub is sized by how you want to sit in it, not by volume alone: some shells are made to sit upright with knees bent, others to recline, and a tall user in a short shell has a genuinely worse experience regardless of price. Filled, even a modest tub is heavy enough that a deck needs checking and a soft lawn will settle under it, so most buyers end up on a paver or gravel base. If the unit is chilled, the base also has to put the chiller somewhere dry with airflow around it, which is easy to forget until delivery day.
Questions people ask about cold tub
Is a cold tub the same as a cold plunge?
In ordinary use yes, they name the same thing. Retailers tend to print cold plunge on the chilled, insulated products and cold tub on the simpler vessels, but there is no formal line between the two words.
Do I need a chiller?
Only if you want a set temperature without buying ice. A plain insulated tub and a regular ice habit reaches the same water temperature; the chiller buys consistency and removes a recurring errand, which is what the extra cost is for.
Can a cold tub go indoors?
It can, but the weight when filled and the need to drain it somewhere are the constraints, not the cold. Most indoor installations end up in a garage or a utility space with a floor drain rather than in a finished room.