A portable ice bath is the cheapest way into cold water: an inflatable or soft-sided tub, a hose, and bags of ice from the gas station. The tub is a one-time cost. The ice is a cost every session.
This page counts the bags for seven portable tubs. For choosing a tub in the first place, start with the ice bath buying guide.
Short answer: at a three-quarter fill, a portable ice bath of 85 to 116 gallons needs about 2 bags of 20 lbs to drop the water by 10°F to 50°F, and about 3 to 5 bags to drop it by 20°F. A 150-gallon tub needs about 3 and 6 bags. Measure your tap water first, because the starting temperature decides the count.
The formula, in one line
Melting a pound of ice absorbs about 144 Btu, the latent heat of fusion (334 kJ per kg). A Btu warms 1 lb of water by 1°F, per the U.S. Energy Information Administration, and a gallon of water weighs about 8.34 lbs, per the U.S. Geological Survey. The meltwater then warms from 32°F to the bath temperature, which adds 18 Btu per pound at a 50°F target.
Ice in lbs = gallons x 8.34 x degrees to drop ÷ 162 (for a 50°F target)
The bag count
Ice to reach 50°F at a three-quarter fill, in 20 lb bags:
| Tub | Listed volume | 3/4 fill | Drop 10°F | Drop 20°F | Drop 30°F |
|---|---|---|---|---|---|
| The Cold Pod | 85 gal | 64 gal | 1.6 bags | 3.3 bags | 4.9 bags |
| Polar Recovery Ice Bath | 370 L (98 gal) | 73 gal | 1.9 bags | 3.8 bags | 5.7 bags |
| SereneLife 105 Gallon | 105 gal | 79 gal | 2.0 bags | 4.1 bags | 6.1 bags |
| Nurecover Pod | 106 gal | 80 gal | 2.0 bags | 4.1 bags | 6.1 bags |
| SaluSpa Arctic Ice | 111 gal | 83 gal | 2.1 bags | 4.3 bags | 6.4 bags |
| The Cold Pod XL | 116 gal | 87 gal | 2.2 bags | 4.5 bags | 6.7 bags |
| Icebound Essentials XL | 150 gal | 113 gal | 2.9 bags | 5.8 bags | 8.7 bags |
Volumes from the makers’ and retailers’ listings, checked September 2026. Bag counts are our arithmetic and are minimums: they leave out heat from the air, the ground, the tub walls, and you. Round up when you buy.
How to read the table
Pick the column by your tap water. If the hose runs at 60°F, you need a 10°F drop to reach 50°F. At 70°F, a 20°F drop. At 80°F, a 30°F drop.
Run the numbers on a summer week. Tap water at 70°F in The Cold Pod XL needs about 4.5 bags a session, so round up to 5. Three sessions a week is 15 bags. Multiply by what a bag costs where you live, and you have the weekly price of the habit.
Why portable tubs differ from rigid ones
The walls on these tubs are thin compared with a foam-filled barrel. The listings describe them in their own terms: quadruple-layer PVC, pearl foam, and nylon for The Cold Pod; 5-layer insulation for the Nurecover Pod; 3mm EPE with 0.3mm PVC for the SereneLife; drop-stitch walls with a weather coating for the SaluSpa Arctic Ice. None of them publishes an R-value, so we can’t rank them on how fast they warm.
Here’s what the spec sheet won’t tell you. Thinner walls don’t change how much ice the first fill needs; the table holds for any wall. They change how fast the water warms back up afterwards, which decides how much ice the next session needs.
Ways to use fewer bags
- Fill lower. At a half fill, you need two thirds of the ice in the table.
- Fill early. Morning water and air are cooler than afternoon.
- Keep the lid on. Six of the seven listings include a lid or cover; our data doesn’t show one for the SaluSpa Arctic Ice, so check before you order.
- Use the shade. Nurecover lists UV-resistant material on the Pod, and Polar Recovery includes an outdoor cover. Shade still helps any tub.
- Make block ice. Haldane’s silicone molds make 6 lbs per batch, per the listing, which suits top-ups.
My rule of thumb: buy the smallest tub you fit in. The Icebound Essentials XL needs about 3 bags where The Cold Pod needs about 2 for the same 10°F drop, every session you own it.
Check the temperature after it melts
Cleveland Clinic suggests beginners start at 50 to 59°F and says never to stay in longer than 5 minutes. Stir the water after the ice melts and read a floating thermometer, since the water near the ice reads colder than the rest.
If the bags add up to more than a chiller would cost, compare ice-free setups in our ice bath comparison.
Bottom line: at a three-quarter fill, plan on about 2 bags of ice per 10°F you need to drop in a 100-gallon portable tub, and about 3 in a 150-gallon one. Measure the tap water before you buy the ice.
Sources
- Physics LibreTexts, “Phase Change and Latent Heat” (334 kJ/kg), accessed October 2, 2026: libretexts.org
- U.S. Energy Information Administration, “British thermal units (Btu),” accessed October 5, 2026: eia.gov
- U.S. Geological Survey, “Water Density” (a gallon of water weighs about 8.34 lbs), accessed October 2, 2026: usgs.gov
- Cleveland Clinic, “Are ‘Cold Plunge’ Ice Baths Good for You?” May 8, 2026: health.clevelandclinic.org
- Product volumes, wall construction, and included lids: The Cold Pod, Polar Recovery, SereneLife, Nurecover, Bestway, and Icebound Essentials listings, checked September 2026; Haldane mold listing, checked October 19, 2026