Hot Tub Supply Spa Depot
 
Tub Terms
Glossary for Users of Hot Tubs and Spas
 SpaCyclopedia Index Spa Simulator Spa Parts Illustrated Glossary

Hot tub spa and pool terminology defined. A glossary to help both novices and seasoned hot tub enthusiasts to gain a better understanding of the terms used in wonderful world of spas.

A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

 
A Acid
Acid Demand
Acrylic
Air Buttons
Air Lock
Air Switches
Algae
Algae Spores
Algaecide
Alkalinity
B Bacteria
Balanced Water
Base
Bather Load
Biofilm
Break Point Chlorination
Broadcast
Bromamines
Brominator
Bromine
BTU (British Thermal Unit)
Buffer
C Calcium Carbonate
Calcium Chloride
Calcium Hardness
Calcium Hypochlorite (Cal Hypo)
Carbonates
Cartridge Filter
Cavitation
Chelating Agent
Chine
Chitin
Chloramines
Chlorine
Circuit Board
Clarifier
Combined Chlorine
Contactor
Corrosion
Cover Protectant
Cover Removal Device
Croze
Cyanuric Acid
D Defoamer
Disinfect
Dichlor
Diverter Valve
Draft Hood
Dry Acid
E Efficacy
Effluent
Enzymes
Equilibrate
F Flocculent
Flow Switch
Free Chlorine
G Ground Fault Circuit Interrupter (GFCI)
Grounding
Gunite
H Halogen
Hard Water
Head
Heater Element
Heater Manifold
Heat Exchanger
Hertz (Hz)
High Limit Switch
Hoops
Hot Tub Folliculitis
Hydrogen Peroxide
Hydrotherapy Jets
Hypobromous Acid
Hypochlorous Acid
I Impeller
Incoloy
Influent
Ion
J Jets
K Kilowatt
Kilowatt Hour
 
L Langelier Index
M Make-Up Water
Monopersulfate Compound
Muriatic Acid
N Nature2
Non-Chlorine Shock
O Organic Contaminants
ORP
OTO
Overflow System
Oxidizing
OxySpa
Ozone
Ozonator
P Peroxide
Peroxymonosulfate
pH
pH Buffer
pH Decreaser
pH Increaser
Phenol Red
Potassium Carbonate
Potassium Monopersulfate
PPM
Precipitate
Pressure Switch
Pseudomonas
Q Quaternary Ammonium
R Relay
Return Inlet
Roto-Molding
R-Value
S Safety Cover
Sanitizer
Scale
Scale & Stain Preventer
Sequestering Agent
Shock
Skimmer
Soda Ash
Sodium Bicarbonate
Sodium Bisulfate
Sodium Carbonate
Sodium Dichlor
Sodium Hypochlorite
Soft Water
Spa Fragrance
Spa Pack
Stabilizer
Staves
Suction Outlet
Superchlorination
T Test Kit
Test Strips
Thermostat
Timer
Titanium Heater
Topside Controls
Total Alkalinity (TA)
Total Chlorine
Total Dissolved Solids (TDS)
Trichlor
Turbidity
Turnover
U Ultra Violet (UV)
Urethane Foam
V Vacuum Ultra Violet (VUV)
Velocity
Volute
Venturi
W Watt
Weir
Winterizing
Working Pressure
X X-Spa
Y Yellow Algae
Z ZorbO
 

Acid
Chemicals such as sodium bisulfate, also called Dry Acid, Muriatic Acid or pH Decrease (Spa Down) used to lower pH or alkalinity.

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Acid Demand
As determined by a test, the proper amount of acid (pH Decreaser) to reach correct levels.

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Acrylic
A very durable and non-porous heat-formable synthetic used to form the shell of high quality spas.

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Air Buttons
Topside spa controls used to activate jets and other spa features.

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Air Lock
A condition which inhibits water circulation, and occurs when air pockets form around the pump or in plumbing, often associated with draining and refilling. Can usually be corrected by slight loosening of the pump fittings and allowing the trapped air to escape.

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Air Switches
Electro-mechanical devices used to control motors and other devices in the spa.

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Algae
Microscopic aquatic plant life which can grow on spa surfaces or float in the water. Although fairly harmless to bathers, algae discolors the water and indicates improper sanitization.

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Algae Spores
Dormant form of airborne algae which is introduced into spa or pool water by wind and rain showers.

Algaecide
A chemical used to kill algae and prevent the re-growth.
Spa Algaecide

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Alkalinity
See Total Alkalinity

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Bacteria
Microscopic organisms continuously entering the water via bathers, airborne dust, etc. Without proper sanitization hot tubs and spas are the ideal breeding ground for bacteria, many of which can cause disease or infection.  See Pseudomonas.

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Balanced Water
Water that is neither corrosive nor scale forming. Water with the proper relationships of pH, total alkalinity and calcium hardness is said to be balanced.

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Base
A chemical which raises pH and/or alkalinity when added to the water such as pH Increase, pH Buffer/Alkalinity Increaser, or Easy pH.

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Bather Load
The number of individuals using a pool or spa in a 24 hour period. This load is the primary source of bacterial and organic contamination. The depth, surface area, and total volume of water are factors as well as the capacity of water purification apparatus such as filters, together with water treatment chemicals and sanitizers.

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Biofilm
Biofilm is a complex association of microorganisms which adhere to a hot tub surfaces, particularly inside the plumbing, where they are difficult to remove. Biofilm may contain bacteria, viruses, mold, parasites as well as dirt and polysaccharides which add adhesion to a surface. It grows in the nicks and crannies within the plumbing systems and jets, forming a slippery film. Microorganisms inside the biofilm layer are somewhat protected from sanitizing agents such as chlorine, bromine, or algaecides. These microorganisms present a danger because if released into the water, a bather may be contaminated before sanitizers can kill them. It is important to remove biofilm and prevent it from reforming.

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Break Point Chlorination
The process of shocking the water with significant quantities of chlorine to oxidize all contaminants and organic wastes and leave all remaining chlorine as free chlorine.

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Broadcast
A method of dosing powdered chemicals into water by spreading them widely over the surface. Most spa chemicals, however, should be dissolved individually in water first, then added to the hot tub water (never mixed together).

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Bromamines
A molecule of combined bromine and ammonia, which unlike combined chorine compounds, continues to have sanitizing ability.

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Brominator
A floating device, such as Floating Bromine-Chlorine Feeder , which holds bromine tablets and dispenses a metered amount of bromine sanitizer into the spa water.

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Bromine
The preferred sanitizing agent for hot tub spas that kills bacteria and algae. The tablet form of this product is dispensed using a floating brominator like the Floating Bromine-Chlorine Feeder. The granular form is added upon spa startup (initial filling) to establish an immediate bromine reserve.

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BTU (British Thermal Unit)
A scale for measuring the capacity of a heating device, such as a gas spa heater. Technically, the quantity of heat required to raise the temperature of one pound of water from 60° to 61°F, at a constant pressure of one atmosphere, is one BTU.

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Buffer
A chemical that resists pH change in spa water, such as sodium bicarbonate or pH Buffer/Alkalinity Increase (Spa Up).

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Calcium Carbonate
A compound which forms in unbalanced water to form scale.

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Calcium Chloride
A soluble white compound used to raise the calcium hardness of spa & pool water, to protect equipment. Hardness Increaser 

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Calcium Hardness
A measure of the amount of calcium dissolved in water. Water with low hardness can lead to corrosion of metal parts. Test strips are available for checking hardness levels - Hardness Test Strips.

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Calcium Hypochlorite (Cal Hypo)
A granular form of chlorine which is commonly used in pools, but not recommended for spas because it may leave unsightly calcium deposits at the waterline and scale buildup in heaters.

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Carbonates
Compounds which are primary in the makeup of Total Alkalinity and TDS.

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Cartridge Filter
The type of filter commonly used in spas consisting of a cylinder of pleated fabric media with end caps.
Filter Replacement Guide

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Cavitation
A vacuum created when the discharge capacity of a pump exceeds the replacement in the suction line. It occurs when the pump is oversized, when the diameter of the influent line is too small, or when there is an excessively long influent line. Cavitation causes bubbling and vibrations that can damage the pump over time, and it also reduces pumping efficiency.

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Chelating Agent
Stain & scale preventing compounds that sequester dissolved metals to prevent water discoloration.
Metal Free Stain, Scale, Metal Control

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Chine
The portion of the stave of a wooden hot tub below the bottom of the croze.

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Chitin
A naturally occurring polymer (pronounced KY-tin) found in crab and lobster shells. As a spa clarifier, it is the best flocculating agent available. Removes oils, dirt, scum, and metal deposits and allows the filtering system to work more effectively. Sea Klear Natural Clarifier (#CA1013).

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Chloramines
Chlorine ammonia compounds (combined chlorine) formed when chlorine reacts with organic contaminates in the water. Chloramines are not effective as sanitizers and are responsible for eye and skin irritation as well as strong chlorine odors.

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Chlorine
A sanitizing agent that kills bacteria and algae.  When Chlorine is used in spas, the proper type is Sodium Dichlor, like our Granular DiChlor.

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Circuit Board
The electronic brains of a spa, containing relays, contactors, and connecting to all other electrical components.

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Clarifier
A compound used to remove dissolved solids, metals, dirt, oils, or other contaminants from spa and pool water. Products like Sea Klear Natural Clarifier, containing Chitin do this naturally 

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Combined Chlorine
The portion of the total chlorine in water in chemical combination with ammonia, organics, and nitrogen, most of which are chloramines.

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Contactor
A relay-type device in a spa's electrical circuit which controls power to another device.

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Corrosion
The etching away of metal fixtures and pump seals due to improperly balanced water.

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Cover Protectant
A special formulation for vinyl spa covers which prevents deterioration caused by sunlight and weather such as 303 Protectant.

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Cover Removal Device
A device to aid in the removal, storage and reinstallation of insulated spa covers.
Cover Lifter Guide

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Croze
The milled grooves in the stave of a wooden hot tub which accommodate the floor planks.

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Cyanuric Acid
Also known as Stabilizer, Isocyanuric Acid, Triazinetrione, or conditioner. A compound that reduces the loss of chlorine in water due to the UV sunlight.

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Defoamer
A compound used to reduce or eliminate foaming in spa water.
Foam Free - Super Defoamer

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Dichlor
See
Sodium Dichlor

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Disinfect
To kill and inhibit growth of harmful microorganisms spa water through the use of a sanitizer such as bromine.

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Diverter Valve
A control valve used to adjust the output of water from jets in various sections of the spa.

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Draft Hood
Part of an indoor gas heater which vents exhaust to the outside to prevent a down draft.

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Dry Acid
A granular chemical, sodium bisulfate like pH Decrease (Spa Down) used to lower the pH and/or total alkalinity.

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Efficacy
The power to produce a desired effect, such as the effectiveness of a sanitizer in spa water.

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Effluent
The water that flows out from a pump or filter.

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Enzymes
Biodegradable proteins which break-down oils, films and digest scum in spa water Scum Buster.

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Equilibrate
To bring to a chemical balance or equilibrium. When adding chemicals to spa water it is advisable to allow a few hours for them to equilibrate with water circulating, prior to testing, in order to obtain accurate readings.

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Filter Media
A pleated, porous synthetic fabric in filter cartridges, used to trap foreign matter. Filter cartridges must be cleaned regularly with filter cleaning compounds like Power Soak Filter Cleaner and Eco-Soak Filter Cleaner to maintain spa water quality.

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Flocculent
A compound which clarifies or flocs spa water by gathering small contaminant particles into larger globules, which then can be easily trapped in the filtering system. for example, Sea Klear Natural Clarifier.

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Flow Switch
See
pressure switch

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Free Chlorine
The amount of chlorine available to kill bacteria or algae.  Also known as Available Chlorine.

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Ground Fault Circuit Interrupter (GFCI)
A fast acting electrical device designed to cut off electricity before it can harm anyone in its path. Required on spas.

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Grounding
Providing or connecting an electric-conducting path to earth. Equipment is grounded for safety, so that in the event of an electrical short to ground, the circuit breaker will trip.

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Gunite
A mixture of cement and sand, sprayed with machinery onto a contoured and reinforced surface to form a pool or spa.

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Halogen
A family of elements which include bromine and chlorine.

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Hard Water
See
Calcium Hardness

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Head
The pressure or resistance in a hydraulic system.

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Heater Element
The portion of an electric heater unit through which electricity flows to produce resistance heat.

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Heater Manifold
A housing for the heater element through which water flows.

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Heat Exchanger
In spas or pools, a device with plates or coiled tubes which transfers heat to water.

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Hertz (Hz)
The measure of the frequency of alternating current expressed in cycles per second. AC current in the U.S. is 60 Hz. In Europe and other parts of the world, 50 Hz is common. 60 Hz. and 50 Hz. electrical devices are not generally compatible or interchangeable.

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High Limit Switch
A safety switch in a heater assembly which shuts off power to the heater element if the temperature becomes too great.

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Hoops
The circumferential bands of a wooden hot tub which prevent the staves from separating.

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Hot Tub Folliculitis
A skin condition often seen where spa sanitation is at fault. See Pseudomonas.

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Hydrogen Peroxide
A compound of hydrogen and oxygen sometimes used as an oxidizer. In concentrated form is normally too dangerous for consumer use.

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Hydrotherapy Jets
Jet fittings in a spa which blend air with water to create a high-velocity, turbulent stream which is stimulating to the skin and body.

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Hypobromous Acid
The strongest disinfecting form of bromine in water.

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Hypochlorous Acid
The strongest disinfecting form of chlorine in water.

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Impeller
Part of a pump which rotates to provide centrifugal force for propelling the water in a recirculation system such as a hot tub or pool.

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Incoloy
A special heat and corrosion-resistant metal alloy used for making heater element sheaths. Titanium has replaced Incoloy as the preferred material for heater elements.

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Influent
Water entering a pump or filter.

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Ion
An atom or group of atoms carrying an electric charge as a result of having lost or gained one or more electrons.  Also a charged subatomic particle (as a free electron). Nature2 works by releasing silver ions, in very small amounts, into the spa water.

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Jets
See
Hydrotherapy Jets

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Kilowatt
A unit of power equal to 1000 watts.

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Kilowatt Hour
A unit of work energy which equals the energy expended by 1 kilowatt in 1 hour.

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Langelier Index
A saturation index used to determine relative water balance by assigning certain values to various levels of total alkalinity, pH, hardness and water temperature.

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Make-Up Water
Fresh source water used to fill or top-off a spa or pool.

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Monopersulfate Compound (MPS)
See
Potassium Monopersulfate

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Muriatic Acid
A form of diluted hydrochloric acid used for reducing pH, and also for dissolving scale from filter cartridges (called Acid Washing).  We recommend a safer alternative: Acid Magic Muriatic Acid Replacement since it will not burn skin, and produces less fumes.

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Nature2
An alternative proprietary spa sanitizing system which does not require the addition of bromine or chlorine. With this product, water must merely be dosed regularly with non-chlorine shock Oxy-Spa Non-chlorine MPS Shock. Lasts 4 months.

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Non Chlorine Shock
An oxygen-based shocking compound, potassium peroxymonosulfate, Oxy-Spa Non-chlorine MPS Shock is fast dissolving so it allows hot tub use just 15 minutes after application (see Shock).

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Organic Contaminants
Wastes such as body oils, perspiration and sun tan residues which bathers introduce into the spa. Most organic wastes will not filter out and must be broken-down by shocking with an oxidizer such as Oxy-Spa Non-chlorine MPS Shock.

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ORP
The oxidation reduction potential or redox produced by strong oxidizers in water. Primarily of concern in pools.

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OTO
A test reagent used to test bromine and chlorine in pool and spa water in liquid test kits.

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Overflow System
See
SKIMMER

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Oxidizing
The process of breaking down organic wastes by the addition of a shocking compound like Oxy-Spa Non-chlorine MPS Shock to the spa water.

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OxySpa
See SHOCK.
Oxy-Spa Non-chlorine MPS Shock

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Ozone
The triatomic (three atom) very reactive form of oxygen that is formed naturally in the atmosphere by a photochemical reaction.  In spas, it is produced by an Ozonator, used for oxidizing contaminants and helping with the disinfecting process.

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Ozonator
An electrically-powered device which produces Ozone.  Ozone is a helper disinfectant, but due to its very short half-life in hot water, cannot do the job of sanitizing spa water all by itself.

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Peroxide
See Hydrogen Peroxide

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Peroxymonosulfate
See Potassium Monopersulfate.

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pH
A scale of the relative acidity/alkalinity of water. The pH scale runs from 0 to 14, with 7 being the neutral midpoint. A pH reading of less than 7 indicates water which is on the acid side of the scale. A pH of more than 7 is on the basic (alkaline) side. In spas, the acceptable range is between 7.2 and 7.8.

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pH Buffer
See Sodium Bicarbonate

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pH Decrease
An acidic chemical used to lower pH or alkalinity. pH Decrease (Spa Down)

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pH Increaser
A base compound, sodium carbonate or soda ash,  used to raise pH & Total Alkalinity like pH Buffer/Alkalinity Increase (Spa Up). Not to be confused with sodium bicarbonate.

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Phenol Red
Chemical reagent used for testing pH in the range of 6.8 - 8.4. Found in liquid test kits.

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Potassium Carbonate
Sometimes sold in liquid form as pH increaser. It is generally more expensive than the powdered pH or alkalinity increasers, but not significantly more effective.

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Potassium Monopersulfate
An oxygen-based shocking compound, such as Oxy-Spa Non-chlorine MPS Shock. This non-chlorine shock is fast dissolving so it allows hot tub use just 15 minutes after application (see Shock). Also called Potassium Peroxymonosulfate. Oxy Shock is also essential for the activation of  sodium bromide (bromine tablets).  The bromide ion by itself has no disinfecting capability.  The monopersulfate compound in OxyShock activates the bromide ion to become bromine, which then rapidly becomes the active sanitizer: hypobromous acid, in spa water.  Upon reaction with bacteria and other contaminants, hypobromous acid is reduced back to bromide ion, ready to be reactivated again by the next dosage of Oxy Shock.

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PPM
Parts per million. (Example: 5 cents in $10,000 = 5 PPM).

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Precipitate
A solid which is forced out of solution in water to form flakes or haze (turbidity) in suspension.

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Pressure Switch
A safety switch which shuts-off power to the heater element if water flow is not detected.

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Pseudomonas
Pseudomonas bacteria can cause Hot Tub Folliculitis, a condition often seen where spa sanitation is at fault. The most common symptom is an itchy rash or small reddish bumps, sometimes confused with bug bites.  Read more about symptoms, causes, and prevention: Spa Microbiology 101.

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Quaternary Ammonium
Organic compounds of ammonia (Quats or QAC) sometimes used as an algaecide.

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Relay
A device in a spa's electrical circuit which controls power to another device.

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Return Inlet
The fitting through which water returns into a spa from the circulating pump.

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Roto-Molding

The rotational molding process begins with a quality mold placed inside a machine that has a  heating and cooling area. Plastic resin beads are poured into each mold. The molds are next conveyed into an oven where they are slowly rotated on horizontal and vertical axis simultaneously. The melting resin sticks to interior sides of the heated mold and coats all surfaces very evenly. It rotates continuously during a cooling cycle so that the finished product retains an even wall thickness for strength. LifeCast Spas spas are roto-molded unibody construction.

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R-Value
The measure of resistance to the flow of heat through a given thickness of a material (as insulation) with higher numbers indicating better insulating properties.   In spa covers, a higher R-Value will save energy costs.

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Safety Cover
A spa cover which meets ASTM standards for strength, construction, and anchoring.

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Sanitizer
A compound such as bromine or chlorine, or a metal ion formulation based on copper or silver,  used to kill microorganisms in spa water.

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Scale
Calcium crust or buildup caused by unbalanced water. These mineral deposits form on spa surfaces and clog filters, heaters and pumps. The regular use of stain prevention chemicals can prevent scale formation.

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Scale & Stain Preventer
A product which prevents the formation of calcium scale and metal stains on spa fittings caused from copper and iron plumbing. For example Metal Free Stain, Scale, Metal Control.

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Sequestering Agent
See
CHELATING AGENTS

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Scum Digester
An enzyme product which breaks down body oils, soap film and lotion residues in spa water, like  Scum Buster.

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Shock
Addition of an oxidizer such as Oxy-Spa Non-chlorine MPS Shock or superchlorinator to break-down the organic contaminates on which bacteria feed. Also called Oxyshock.

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Skimmer
The skimmer is a basket, usually located above the filter.  Its purpose is to collect large debris and prevent it from reaching the filter.  Use of  Skimmer Sock Pre-Filters over the skimmer will further decrease the amount of debris which would otherwise reach the filter, and make filter cleaning easier. 

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Soda Ash
Common term for sodium carbonate such as pH Increase - pH & TA Increaser which is used to raise pH and Total Alkalinity of spa water.  Sodium carbonate or soda ash has a pH of 13.

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Sodium Bicarbonate
Commonly used to increase the Total Alkalinity (TA) of spa water for example pH Buffer/Alkalinity Increase.  The uncommon chemical name is Sodium Hydrogen Carbonate (not to be confused with Sodium Carbonate.)  If the water's pH is below the normal range, raising the TA with this chemical will often buffer the pH or bring it into proper range.  Sodium bicarbonate has a pH of 8.3.

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Sodium Bisulfate
Also known as dry acid, the chemical used to lower pH and total alkalinity of spa water (pH Decrease).

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Sodium Carbonate
See Soda Ash
pH Increase - pH & TA Increaser

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Sodium Dichlor
The type of chlorine which is most effective for use in spas.  Sometimes used as a sanitizer, and is a very good shock for problem spas, particularly when cloudiness due to high bather load is a factor.  Chemical names: sodium dichloro-isocyanurate and sodium dichloro-s-triazinetrione. Also called Dichlor. Granular DiChlor.

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Sodium Hypochlorite
The form of chlorine in liquid household bleach.  Not recommended for spas because it has limited effectiveness in hot water, adversely affects pH balance, and can damage spa surfaces if spilled or splashed.

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Soft Water
Water with very low levels of dissolved calcium. Can be corrected with calcium hardness increaser like Hardness Increaser.

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Spa Fragrance
Special perfumes designed to enhance the hot tub experience and overcome chemical odors. These are designed for spas, and will not alter water balance or clog filters Spa Fragrance Department.

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Spa Pack
An integrated unit consisting of electronic or mechanical controls, which may include a water pump, GFCI and other devices.
Spa Pack Department

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Stabilizer
See
CYANURIC ACID

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Staves
The vertical boards of a wooden hot tub.

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Suction Outlet
The fitting, often near the skimmer, through which the water is drawn from the spa.

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Superchlorination
Application of large shock dosages of chlorine to destroy buildup of organic contaminates in water. An alternative is to use a non-chlorine shock like Oxy-Spa Non-chlorine MPS Shock.

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Test Kit
A set of chemical solutions and color references for testing pH, total alkalinity and sanitizer levels of spa water.  We recommend instead the use of Test Strips which are very accurate and much easier to use.
Test strips and kits

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Test Strips
Easy-to-use dip strips for measuring the pH, total alkalinity and sanitizer levels of spa water. Strips are also available for testing water hardness levels.
Testing supplies

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Thermostat
A device, either electronic or mechanical, which controls the operation of the heater by sensing water temperature.

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Timer
A clock that automatically controls the pump and other devices in a spa.

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Titanium Heater
Titanium is the most durable and chemically-resistant metal for use in spa heater elements. Since it contains no iron, it cannot rust and is far more resistant to corrosion and scale formation than Incoloy. Titanium hot tub heaters typically last 2 to 3 times longer than Incoloy or coated heater elements.

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Topside Controls
A set of button or knob switches, either pneumatic or electronic, for controlling a spa's pump, jets, heater, and other features.

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Total Alkalinity (TA)
The measure in PPM of all the dissolved base/alkaline material in the water. The acid-neutralizing capacity of water which indicates its buffering ability, or resistance to fluctuations in pH.

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Total Chlorine
The sum of combined and free chlorine.

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Total Dissolved Solids (TDS)
A measure of the amount of matter which is in solution in spa water.  This includes: calcium, magnesium, carbonates, bicarbonates, metallic compounds, etc.

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Trichlor
Another form of chlorine, often supplied in tablet form, and used for pools.   Not recommended for spas and hot tubs because of its acidic nature.  Prolonged contact with spa shell may bleach or permanently mar the surface.

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Turbidity
A cloudy condition in water due to the presence of suspended particulates or precipitated material such as scale.

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Turnover
The time period required to completely circulate an amount of water equal to the volume of a vessel, such as a pool or spa.

Ultra Violet (UV)
With regard to spas, Ultra Violet light is a part of the light spectrum that is particularly damaging to vinyl spa covers.  Use of a Cover Protectant, such as 303 Protectant, blocks UV rays to prolong cover life.

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Urethane Foam
A spray-in insulating material used in hot tubs. Reduces heat loss and also provides some structural support for plumbing and cabinet shell.

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Vacuum Ultra Violet (VUV)
The light frequency in which ozonators operate.

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Velocity
Water movement rate, as measured in gallons per minute or feet per second.

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Venturi
A tube with a tapering constriction in the middle that causes an increase in the velocity of flow of a fluid and a corresponding decrease in fluid pressure.  In spas, Venturi fittings with side drafts are sometimes used to introduce air into jet features, and to pull ozone from Ozonators into the spa water.

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Volute
A pump housing containing an impeller and a diffuser.

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Watt
A derived unit of electrical power. Amps x Volts = Watts.

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Weir
A part of a hot tub or pool skimmer that automatically adjusts to water level.

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Winterizing
The procedure of preparing spas for freezing weather, in cold climates when the spa will not be operated.  May include draining and cleaning the shell, and opening connections to release water from plumbing and heaters.  Most people continue to heat and operate their spas in winter; for them, winterizing is not necessary if appropriate measures are taken to prevent freeze-up.
Spa Winterizing info

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Working Pressure
A specification of maximum operating pressure, as recommended by an equipment manufacturer.

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X-Spa
A series of rotationally-molded hot tub models.

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Yellow Algae
A variety that clings to pool walls, also known as mustard algae. Typically found in shady areas. Very resistant to normal levels of chlorine.

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ZorbO
The brand name of a very effective oil scum absorbing product.  Wicks scum without absorbing spa water.
ZorbO Scum Absorber

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Spa Depot, The, Spas & Hot Tubs - Dealers, Olympia, WA
 

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