Hot Tub Glossary

Acid
A solution with a pH of less than 7.

Acrylic
Durable plastic material used in hot tub construction.

Algae
Simple plant life which grows in standing water. Algae tends to be slimy in texture and there are several different varieties. Keeping your hot tub clean will prevent algae.

Alkali
A solution with a pH higher than 7.

Biguanide
A sanitiser used in non-halogen based water treatment systems (i.e. without bromine or chlorine). Incompatible with most chemicals used in chlorine or bromine based hot tub treatments.

Bromamines
A combination of bromine and ammonia. Less odorous than chloramines.

Bromine
A halogen used for cleaning hot tub water. Not as strong as chlorine.

Clarifier
A chemical used to remove cloudiness from hot tub water. It clumps particulate matter together so that it can be filtered out.

Chlorine
A halogen which is used to sanitise and oxidise hot tub water. It kills bacteria and algae.

Chlorinator
A canister which releases bromine or chlorine into the hot tub water as they slowly dissolve.

Cedar
A type of wood sometimes used for hot tub exteriors.

Calcium Hypochlorite
A granular chlorine based sanitiser.

Calcium Hardness
A measure of the proportion of calcium salts in hot tub water. Needs to be monitored to prevent build-up of scale, especially on heating elements.

Disinfectant
A chemical that kills bacteria. May also have a deodorising effect.

Defoamer
A chemical to reduce or eliminate foaming in hot tubs and spa pools.

Foam
Bubbles which may form on the surface of the water in a hot tub or spa. Also, insulating foam may be sprayed on the underside of the hot tub shell to reduce heat loss.

Flow Rate
A measure of how much water passes through a hot tub pump. Measured in gallons per minute.

Flow Monitor
A gauge to measure how fast water is flowing through the hot tub's plumbing system.

Filter
A porous fibrous material which allows water to pass through while collecting particles, oils and foreign debris. In hot tubs it is usually in the form of a cylindrical cartridge.

Fiberglass
A material which is shaped to form the shells of hot tubs and spas.

Generator
A device which makes chlorine from dissolved salt in the hot tub water, as it is pumped through an electric cell.

Hydrogen Peroxide
A non-chlorine based oxidiser or shock used with biguanide hot tub systems. Handle with extreme care.

Humidity
The amount of water vapour held in the air. In excess can cause mould or mildew to form, especially in indoor hot tub rooms.

Ionizer
A device which kills bacteria and algae in a hot tub through generating copper, zinc and/or silver ions.

Intake
An opening in the hot tub shell usually protected by a grating, through which water is pumped through the filtering system.

Insulation
A material surrounding the hot tub shell to prevent heat loss and reduce noise. Usually foam based.

Jet
An opening in the hot tub's shell through which water is pumped into the hot tub, providing a massaging, bubbling or whirlpool action.

Jacuzzi
Actually a specific brand of hot tub, Jacuzzi were the first firm to manufacture hot tubs and spas. However the term is now more commonly used to refer to any hot tub, regardless of manufacturer.

Lithium Hypochlorite
A sanitiser for hot tubs and spas which lacks a strong odour and has a long shelf life.

Lighting
A wide variety of coloured mood lighting is available for many hot tubs, both around the hot tub surround and underwater within the tub itself.

Main Drain
Typically located at the lowest point of the hot tub shell this is an opening through which the water can exit.

Non-Chlorine Shock
A shock such as potassium peroxymonosulfate or hydrogen peroxide. Eliminates most bromamines and chloramines.

Ozone (O3)
A gas consisting of oxygen molecules with 3 atoms. Less stable than the more common O2. Kills bacteria and helps to purify water.

Ozonator
A device for generating ozone, which is used to disinfect and deodorise hot tubs.

Oxidiser
A chemical which is introduced into hot tubs and spas to burn up organic matter.

Organic Matter
Substances such as pollen, dead skin, perspiration or urine which can give rise to algae growth or buildup of chloramines if the hot tub water is not oxidised regularly.

PVC
Polyvinylchloride. A plastic commonly used in plumbing and piping for hot tubs and spas.

Pump
Moves the hot tub water through the heating and filtration systems.

Priming
Starting the flow of water into a pump so that when it is turned on it is not trying to pump empty air.

PPM
Parts per million. A measure of the concentration of a chemical.

Potassium Monopersulphate
A type of no-chlorine shock used in hot tubs and spas.

Polyethylene
A plastic sometimes used in the construction of hot tub cabinets.

Pink Slime
A type of algae or bacteria buildup which can occur in hot tubs using biguanide.

pH
Potential Hydrogen. A measure of the acidity or alkalinity of a solution. A pH of 7 is neutral, lower than 7 is acidic, and higher than 7 is alkaline.

Residual
Chemicals such as bromine or chlorine remaining in hot tub water.

Reagent
A substance used in water testing for hot tubs. May be in the form of a tablet, a liquid or a powder.

Super Chlorinate
To use a large amount of chlorine as a shock to break down chloramines and prevent odours.

Strainer
A basket which collects debris in some types of hot tub pump to prevent clogging and ensure smooth water flow.

Soda Ash
A chemical used to raise the pH of water in hot tubs and spas.

Skimmer
A compartment which collects debris from hot tub water as it flows to the filter system.

Shock Treatment
Adding an oxidising chemical to the water in a hot tub or spa to oxidise and break up contaminants like perspiration, dirt and substances such as cosmetics or suntan oil.

Shock
Used to describe both the process of shock treatment of a hot tub and the products used to perform it.

Sequestering Agent
A chemical which helps to ensure that minerals remain in solution and do not precipitate out to form scale or stain the surface of the hot tub. Also known as a chelating agent.

Scale
A hard deposit of calcium carbonate which can build up on surfaces within a hot tub, especially areas such as heating elements. Most common in hard water areas. Also known as limescale.

Sanitiser / Sanitizer
A chemical used to kill bacteria in hot tubs. Examples include bromine, chlorine, biguanide, sodium hypochlorite, calcium and lithium.

TDS
Total dissolved solids. A measure of the proportion of solids dissolved in the hot tub water, which can cause foaming and hamper sanitising.

Test Strip
A strip of paper featuring different reagents. When dipped into hot tub water it changes colour, indicating the water quality.

Test Kit
A selection of reagents for measuring different water quality parameters.

Urethane Foam
Used as an insulator in some hot tubs and spa baths.

Valve
A device to control the flow of a fluid in a pipe. For example typically only allows flow in one direction.

Weir
A pivoting flap in a skimmer that prevents debris from floating back into the hot tub.

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