How Water-Circulating (Circulatory) Cooling Works

Water-circulating cooling — often called circulatory or liquid cooling — is the deepest personal cooling AlphaCool makes. A small pump pushes ice-chilled water from a reservoir through a network of tubing sewn across the vest’s torso, continuously carrying heat away from your core and back to the ice. It is the same class of technology NASA builds into spacesuits, where chilled water flows through roughly 300 feet of tubing against the astronaut’s body to shed excess heat (see Sources) — packaged here for jobsites, motorcycles, and sidelines.

This page is the circulatory deep dive from our Cooling Technology Hub. It explains the mechanism, compares the three AlphaCool systems — 5V Touch, 7V, and 12V Motorcycle — and lays out the honest trade-offs.

How water-circulating cooling works

The system is a closed loop with four parts: a cold reservoir (a freezable bladder, refillable ice packs, or a cooler), a compact battery-powered pump, channels of tubing embedded in a mesh vest liner, and the water itself. Switch the pump on and chilled water streams through the tubing, absorbing heat through direct contact with your torso. The warmed water returns to the reservoir, where the melting ice absorbs that heat and sends the water back out cold. The loop repeats until the ice is spent.

Two properties make this the strongest wearable cooling method. First, water is an excellent heat carrier — far better than still air — so heat moves out of your body quickly wherever tubing touches. Second, the cooling is continuous: instead of a static pack that warms up against your skin, fresh cold water keeps arriving every second the pump runs. And because none of this depends on evaporation, performance is identical in dry and humid climates.

The pedigree is real. Liquid-cooled garments began as tube-lined underwear pumped with chilled water for pilots, were adopted and refined by NASA for the Apollo program, and remain the way spacewalking astronauts stay cool inside sealed suits today. The same NASA-derived approach has since spun off into medical, athletic, and industrial cooling (see Sources).

The three AlphaCool circulatory systems

System	Power	Cold source	Cooling duration	Water temperature	Designed for
5V Touch Button	5V 10,000mAh battery (included); pump runs up to 8 hours per charge	4 refillable ice packs	1–3 hours per set of ice packs	Tracks the ice packs as they melt	Simple one-size everyday cooling (fits 33″–44.5″ chest)
7V System	7.4V 2200mAh battery and charger (included); 3-speed switch	2.5L freezable quick-release bladder	2–4 hours per frozen bladder; 1–3 hours with ice cubes	36°F–68°F	Work shifts and high-heat active use; paired sizes XS/S–3XL/4XL
12V Motorcycle	12V SAE motorcycle power cord; optional 7.4V battery sold separately	6L cooler with pump circulation unit and 3 ft extension hose	Up to 6 hours per ice load	36°F–50°F	Motorcycle and ATV riders; paired sizes XS/S–3XL/4XL

All three share the same core idea — pumped ice water against your torso — and differ in where the cold comes from and how they’re powered.

What circulating water feels like

Expect the coldest sensation in personal cooling: the 7V system circulates water in the 36°F–68°F range and the 12V system holds 36°F–50°F, versus the steady 64°F of a phase change vest. Because the chill is spread across the whole tubing network rather than concentrated in one pack, it reads as an even, deep cool across your torso instead of cold spots. The 7V pump runs at a quiet 48 dBA — a faint hum you stop noticing quickly.

What water-circulating cooling is best for

Motorcycle and ATV riders. The 12V system plugs into your bike’s SAE connector and cools for up to 6 hours per ice load — ride-long relief inside protective gear.
Long shifts in serious heat. Continuous heat removal for hours suits outdoor labor, industrial floors, and event crews.
Humid climates. Conduction into cold water works regardless of humidity, where evaporative gear slows down.
Athletes and heavy exertion. A British Journal of Sports Medicine meta-analysis found cooling during exercise (percooling) significantly improves performance in the heat (see Sources).
Anyone who wants the coldest option. If 64°F PCM relief isn’t enough, pumped 36°F water is the step up.

Browse the range: Circulatory Cooling Vests and Water Cooling Vests.

Honest limitations

Ice logistics. Cooling time is bounded by your ice supply. You’ll need freezer access for bladders, or ice for the packs and cooler — and a spare 7V bladder if you want to swap and go.
More hardware to manage. Pump, tubing, battery or power cord, and reservoir all need filling, draining, and drying. It is the most capable system we sell, and also the most involved.
Weight and cost. Reservoir plus water makes these heavier and pricier than evaporative or PCM gear.
The 12V is happiest tethered. It runs off motorcycle power by design; going cordless means adding the optional 7.4V battery (sold separately).
Cooling is not a license to skip heat safety. NIOSH lists heat stroke, heat exhaustion, heat cramps, and heat rash among heat-related illnesses — hydration, shade, and rest breaks still apply (see Sources).

Setup and care basics

Freeze ahead. Put the 7V bladder (or the 5V ice packs) in the freezer the night before; for the 12V, load the 6L cooler with ice just before the ride.
Purge and connect. Fill, connect the quick-release fittings, and let the pump run a moment so water reaches every channel before you head out.
Drain and dry after use. Empty the bladder or cooler, run the pump dry briefly, and air-dry components fully before storing to keep the loop fresh.
Mind the battery. Charge with the included charger only, and top it up periodically during the off-season.

Water-circulating cooling FAQ

How long does a water-cooled vest stay cold?

The 7V system cools 2–4 hours per frozen bladder (1–3 hours if you fill it with ice cubes instead), the 5V Touch runs 1–3 hours per set of ice packs with up to 8 hours of pump battery, and the 12V system’s 6L cooler supports up to 6 hours of cooling.

Do the batteries come included?

The 5V Touch includes its 10,000mAh battery and the 7V system includes its 7.4V battery and charger. The 12V system runs off your motorcycle’s SAE power connection; its 7.4V battery is optional and sold separately.

How cold does the water actually get?

As cold as your ice makes it: the 7V system operates between 36°F and 68°F, and the 12V system between 36°F and 50°F. Water temperature drifts upward as the ice melts, which is why duration figures are ranges.

Which system should motorcycle riders choose?

The 12V Motorcycle system. It wires to the bike with the included SAE cord, carries its 6L cooler in a strapped motorcycle bag, and includes a 3 ft extension hose for comfortable routing.

Does humidity affect performance?

No. Heat moves from your body into the circulating water by direct contact, so muggy air changes nothing — a key advantage over evaporative cooling.

Can I buy a replacement bladder?

Yes — the 2.5L quick-release bladder for the 7V vest is sold separately. Keeping a second one frozen doubles your effective cooling window.