ModTub Cold Plunge Review: Good Hardware, Confused Numbers

Who makes it

Modtub is MODTUB LLC of Dallas, Texas. The about page credits two brothers, Jesse and Sawyer, who left jobs in accounting and supply chain, started a hot tub company, found the market saturated, and pivoted to cold plunges. The tub began as a garage project.

Small note before the numbers. The about page says the company was founded in February 2023. The Better Business Bureau profile records the business as started on 23 February 2022. That is a year apart. It is trivial on its own, but it sets the pattern for everything below.

The capacity claim does not survive

We check every capacity claim against the brand’s own dimensions, because this category fails that test constantly.

Modtub’s product page lists interior dimensions of 40.5 inches long by 22 wide by 24 high. Multiply those out and you get 21,384 cubic inches, which is 92.6 gallons. That is the figure for a perfect rectangular box with square corners. A rotomolded tub with radiused corners and tapered walls holds less than its bounding box, so the true brim volume is below 92.6.

The same page says the tub holds 122 gallons filled to the brim.

That is about 32 percent more water than the stated interior can physically contain. The page also says 90 gallons is the normal fill level, which would put the water at 23.3 inches deep in a 24 inch tub. Nobody sits in a tub filled to within three quarters of an inch of the rim.

Which is wrong, the dimensions or the gallons

Probably the dimensions, and here is why that matters more than it sounds.

The Rogue Fitness listing for the same Modtub 2.0 gives a tapered interior: 54 by 32 inches at the top, 46 by 22 at the bottom, 27 inches deep. Note that 22 inch bottom width, which matches modtub.co exactly. So modtub.co appears to be publishing the floor of the tub as its interior dimensions.

Run the tapered volume properly and Rogue’s numbers give roughly 159 brim gallons. Against that, 122 at the brim and 90 in use are both conservative and sensible.

So the tub is almost certainly fine and the spec sheet is wrong. But look at what the wrong spec sheet does to a buyer. Someone six feet tall reading modtub.co sees a 40.5 inch interior length and rules it out. The real interior length at the shoulders is closer to 54 inches. One published number scares off buyers who would fit, while the number next to it oversells the water. Two errors pointing in opposite directions on the same page.

If you are working out whether you fit, our tub sizing guide explains which measurement actually decides it.

What the other sellers say

Four sources, four capacities for one tub:

• Modtub: 90 gallons normal, 122 brim
• Garage Gym Reviews: 92 gallons
• The Cold Plunge Store: 85 to 90 gallons
• Plunge Reviews: about 75 gallons

That is a 47 gallon spread, which is roughly 390 pounds of water. Garage Gym Reviews also lists the tub as 72 inches long, but The Cold Plunge Store lists a total footprint of 72 by 40 inches including the chiller, so that looks like a footprint reprinted as a tub dimension.

The weight figures do reconcile

Credit where it is due. Water runs about 8.34 pounds per gallon. Modtub lists 95 pounds dry and 90 gallons, which gives 845.6 pounds filled. The page says 850. That is within half a percent, so somebody did the sum.

What is missing is the brim figure. At the 122 gallons the brand advertises, the tub weighs about 1,112 pounds. If you are putting this on a deck or a balcony, that is the number to design around, and Modtub does not print it anywhere.

The chiller cannot hit its own top speed

The chiller is quarter horsepower and rated at 3,010 BTU. Modtub publishes both, which is good practice.

Now do the physics. Ninety gallons of water weighs 750.6 pounds, and one BTU moves one pound of water by one degree. So 3,010 BTU an hour divided by 750.6 pounds gives 4.01 degrees an hour, and that is with zero heat leaking in, a perfectly insulated tub and no losses in the hoses. It is a ceiling nothing can beat.

The advertised rate is 3 to 5 degrees an hour. The 3 is realistic. The 5 is not physically available. You would need about 3,750 BTU to reach it, which is a bigger chiller.

Fill to the 122 gallons the same page advertises and the ceiling drops to about 3 degrees an hour, meaning even the bottom of the claimed range becomes unreachable at the brim.

The one measurement we can point at comes from Plunge Reviews, whose Modtub 2.0 review, last updated 14 August 2025, says “in our tests, it took about 9 hours to cool the water from 75°F down to 43°F”. That is 32 degrees in 9 hours, or about 3.6 degrees an hour, which sits between our calculated ceiling and the honest end of the brand’s claim. Read it with the usual caution. Plunge Reviews names the Modtub its best value pick, hands out a discount code for it and earns on the chiller, so it is not a neutral party, and we have not repeated the test ourselves. Taken at face value, the physics and the brand’s low end agree. Only the marketing high end does not.

Worth noting separately: The Cold Plunge Store sells a ModTub and advertises 8 to 10 degrees per hour from the same quarter horsepower chiller on 85 to 90 gallons. That needs somewhere between 5,700 and 7,100 BTU. It is roughly double to triple what the stated hardware can produce. Buy from the brand’s own site and you get the honest version of the claim. Our chiller comparison covers what horsepower buys you at each tub size.

The running cost claim is the good news

Modtub publishes 115 kWh a month to hold 43 F through a Texas summer, and prices it at about 26 dollars.

Divide those and the implied electricity rate is 23 cents a kWh. The EIA put the US residential average at 18.83 cents in April 2026. So Modtub costed its own claim at a rate about 22 percent above the national average. At the real average, the same 115 kWh comes to around 22 dollars a month.

That is a brand making itself look worse than it is, which we see maybe once a year.

The consumption figure also passes a sanity check. The chiller draws up to 4.7 amps at 120 volts, or about 564 watts. Running flat out for a full month would be around 412 kWh, so 115 kWh implies the compressor is on roughly 28 percent of the time. For a tub with two inches of foam and a gasketed lid, sitting in Texas heat, that is believable. See our running cost breakdown for why your own bill will differ.

The pump claims hold up too. Rated flow is 3,800 litres an hour, which is 1,004 gallons an hour, and Rogue lists 1,003 GPH. On 90 gallons that is 11 turnovers an hour, so the marketing claim of five or more passes with room to spare.

What you give up

No returns. Once it ships, the purchase is final. Cancel beforehand and you pay 10 percent of the order. On a freight item you have never seen, sold with dimensions that contradict themselves, that is the term that should give you pause.

One year of warranty, non transferable, covering tub, chiller, pump, filter, cord and hoses. Freezing damage, UV exposure, wrong water chemistry and poor maintenance all void it. Shipping damage must be reported inside three days with photographs, so inspect the pallet before the driver leaves.

The BBB profile shows a C rating, not accredited, with two complaints on file and one the company did not answer. Two complaints is a small sample and we are not going to pretend it proves anything about reliability. But a non response rate of one in two is the part worth noticing, because the thing that matters when a chiller dies is whether anyone picks up.

Cheaper ways to the same water

If you like the format, a rotomolded insulated tub around 90 gallons bought on its own costs a fraction of the bundle. Add a chiller separately.

If you want this exact cooling performance for less, a standalone quarter horsepower chiller is the same class of unit doing the same job, and you can pair it with a tub you have already measured yourself.

If 3 degrees an hour is too slow, step up to a 1 HP chiller with an external filter. That is roughly four times the cooling on the same water and turns an overnight wait into a couple of hours.

Our verdict

The Modtub is probably a good tub sold behind a bad spec sheet. The insulation is real, the energy numbers are honest to the point of self sabotage, and the pump and filtration claims check out.

But the brand publishes a capacity a third larger than its own dimensions allow, prints a cooling rate its own chiller cannot reach, gives four different sizes across four sellers, and then refuses to take the thing back. Measure your space against the Rogue dimensions rather than the ones on modtub.co, accept that you are buying an overnight cooler rather than a fast one, and understand that the decision is final at the moment the pallet leaves.

If you would rather keep the option to change your mind, our tub comparison lists options where returning it costs nothing.