Float Tank Glossary
Plain-English definitions for the terminology used across float tank manufacturing, operation, and the wider flotation industry.
For broader context, see the buyer's guide and the float tank types comparison.
A
- ACoS
- In a float center business context, ACoS (Advertising Cost of Sale) is the percentage of revenue spent on advertising to acquire a float booking. It's used to evaluate the efficiency of paid acquisition channels (Google Ads, Meta Ads) against the average revenue per float. A healthy ACoS varies by market but is typically benchmarked against the contribution margin of a single session.
C
- Cabin
- A walk-in float tank with a full-height door, typically rectangular and large enough to stand inside. Cabins offer easier ingress for taller or larger users than pods and accommodate users who feel claustrophobic in enclosed pods. See float tank types for a side-by-side comparison.
D
- Dead Sea effect
- The buoyancy created by very high salt saturation, named after the Dead Sea where natural salinity allows people to float effortlessly. Float tanks reproduce this effect with roughly 800-1,200 lbs of Epsom salt dissolved in 10 inches of water, producing a specific gravity around 1.25.
E
- Epsom salt
- The common name for magnesium sulfate (MgSO₄·7H₂O), the mineral salt dissolved in float tank water to create buoyancy. Most float tanks use 800-1,200 lbs of Epsom salt to reach the specific gravity required for effortless floating. Epsom salt is also gentle on skin compared with sodium chloride at equivalent buoyancy levels.
F
- Filtration cycle
- The automated process a float tank runs between sessions to filter, sanitize, and circulate the saltwater solution. A typical cycle pumps the tank's full water volume through a particulate filter (often 1-10 micron) several times, with sanitation injected via UV-C, ozone, or hydrogen peroxide. Cycle length varies by manufacturer but is commonly 15-25 minutes.
- Float pod
- An enclosed, capsule-shaped float tank with a curved lid that opens upward. Pods are space-efficient and the most common commercial format. See the float tank types comparison for how pods differ from cabins, open pools, and tents.
- Float room
- A converted room (or purpose-built room) that functions as a float environment, often with a built-in shallow pool rather than a discrete tank unit. Float rooms accommodate larger users and couples and are common in spa settings where the room itself is part of the experience design.
- Float suite
- A premium float installation that combines a float room or large cabin with a private bathroom, shower, and changing area inside the same lockable suite. Suites are common in higher-end float centers and reduce shared-facility friction between sessions.
- Float tent
- A lower-cost, soft-walled float tank that sits over a shallow pool of saltwater. Tents (originally popularized by the Zen Float Tent) are aimed at home users and are usually less expensive than rigid pods or cabins. See float tank types for trade-offs.
- Float therapy / Flotation therapy
- The therapeutic use of floating in a high-salinity, light- and sound-restricted environment for stress reduction, recovery, and other reported benefits. Often used interchangeably with REST in commercial settings, though "REST" is the more precise research term.
H
- H₂O₂ (hydrogen peroxide)
- Hydrogen peroxide, used as a sanitizer in some float tanks either alone or as part of a multi-stage sanitation system. H₂O₂ breaks down into water and oxygen, leaving no chemical residue, which makes it attractive for the saltwater environment. Concentration is monitored regularly to maintain effective sanitation.
I
- Inline heater
- A heater plumbed into the filtration loop that warms the saltwater as it circulates, rather than heating the tank water directly. Inline heaters are common in modern float tanks and are typically titanium-bodied to resist corrosion in the high-salt environment. See titanium heater.
- Isolation tank
- An older name for a float tank, emphasizing the isolation from external sensory input. The term dates to John C. Lilly's original research and is still used interchangeably with "float tank" and "sensory deprivation tank."
J
- John C. Lilly
- American physician and neuroscientist who designed the first isolation tanks in the 1950s while researching the effects of sensory restriction on the human nervous system. Lilly's later experiments are controversial, but his early tank designs are the direct ancestors of every modern float tank.
M
- Magnesium sulfate
- The chemical name for Epsom salt (MgSO₄·7H₂O). Magnesium sulfate is preferred over sodium chloride for float tanks because it reaches high specific gravity at lower irritation levels and is gentler on skin, mucous membranes, and equipment.
O
- Ozone sanitation
- A sanitation method that injects ozone (O₃) into the filtration loop to oxidize contaminants. Ozone is highly effective and leaves no chemical residue (it converts back to oxygen) but requires a generator and careful integration with ventilation. Many commercial float tanks combine ozone with UV-C for redundant sanitation.
P
- pH
- A measure of how acidic or alkaline the float tank solution is. Most float tanks target a pH around 7.2-7.6, similar to a swimming pool, which is comfortable for skin and supports effective sanitation. pH is tested regularly and adjusted with food-grade acids or bases.
R
- REST (Restricted Environmental Stimulation Therapy)
- The clinical/research term for the practice of reducing external sensory stimuli for therapeutic effect. Float tanks are the most common modern delivery mechanism for REST. See the buyer's guide for context on REST in the broader float industry.
S
- Salt saturation
- The concentration of dissolved salt in the float tank solution, typically expressed as specific gravity. Float tanks operate at near-saturation for magnesium sulfate in water, producing the Dead Sea effect. Saturation is monitored because evaporation, top-ups, and bather load all shift the concentration over time.
- Sensory deprivation
- The reduction or removal of external sensory input (light, sound, touch, gravity sensation) to a near-minimum. Float tanks aim to reduce — not eliminate — sensory input, which is why "REST" (Restricted Environmental Stimulation Therapy) is the more accurate technical term.
- Sensory deprivation tank
- A common name for a float tank, used interchangeably with "isolation tank" and "float tank." The term emphasizes the reduction of external sensory input that the tank produces, though "REST" is the more precise research term.
- Skin temperature (93.5°F / 34.2°C)
- The water temperature most float tanks target, chosen so the user can no longer perceive the boundary between water and skin. Sitting roughly 5°F below internal body temperature, this temperature minimizes thermal sensation and contributes to the experience of floating without feeling the water.
- Specific gravity
- A measure of the density of the float tank solution relative to plain water (specific gravity 1.0). Float tanks operate at roughly 1.20-1.30 specific gravity, which is dense enough to make even larger users float effortlessly. See salt saturation for how this density is achieved.
T
- Titanium heater
- A heating element with a titanium-clad housing, used for inline heating in float tanks because titanium resists corrosion in high-salinity water. Titanium heaters are now the de facto standard in commercial float tanks.
- Turnover rate
- How often the full water volume of a float tank passes through the filtration system per filtration cycle. Higher turnover rates filter the water more thoroughly between sessions but require more powerful pumps and longer cycles. Commercial float tanks typically aim for 3-5 full turnovers per cycle.
U
- UV-C sanitation
- A sanitation method that exposes circulating water to ultraviolet-C light to inactivate microorganisms. UV-C requires no chemicals and is widely used in float tanks, often paired with ozone or hydrogen peroxide for layered sanitation. Bulb life is finite and replacement is part of routine maintenance.
W
- Waterbed-style heater
- A heating mat (similar to a waterbed heater) placed beneath the float tank to warm the water from below. Waterbed-style heaters are common in lower-cost and home float tanks because they are inexpensive and reliable, but they heat more slowly than inline heaters.
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