Acrylic: A durable and nonporous material used to form the hot tub surface.

Air Leak: Results when connections on the pump’s suction side are not air tight. Pumps need to create a vacuum to work properly. Air leaks can cause high pressures which can damage the pump, filter or both. Aerated water can cause foam.

Air Lock: Results when air bubbles form in the plumbing, usually during draining and refilling. Ask your dealer for the best remedy based on your brand.

Algae: Small plant life which rarely grows in hot tub water. Often green, yellow or black, algae is slimy in texture. Yellow and black variations are hardest to kill. Algae is rare in hot tubs.

Algaecide: Used to kill algae. Algaecide can cause foam. Alkalinity: How alkaline is measured in hot tub water, i.e. above 7.0 pH (see Total Alkalinity).

Alum: Aluminum sulfate, commonly called floc, is used to help clarify water. Causes small particles to lose suspension so they can be vacuumed. Alum lowers the pH of the water (see Floc).

Aluminum Sulfate: See Alum. Biguanide: (Pronounced BY-GWAN-EYED) A sanitizer which is part of a non-halogen (bromine or chlorine) water treatment system. Most chemicals used with chlorine are incompatible with biguanide treated hot tubs, and vice versa. The shock (see Shock) for biguanide treated hot tubs contains hydrogen peroxide.

Broadcasting: Sprinkling a granular chemical over the water surface. Bromine: A sanitizer similar to chlorine and one of the original hot tub sanitizers. Bromine is very effective against bacteria. Unlike chlorine, it sanitizes when combined with ammonia (see Bromamine).

Bromamines: An ammonia and bromine combination which, unlike chloramines, does not have a strong smell. Calcium Chloride: Added to raise calcium hardness.

Calcium Hardness: A measure of the level of calcium salts in the water. Helps determine how scaling or corrosive the water is. It is especially important to monitor calcium hardness for possible build-up on heater elements.

Calcium Hypochlorite: A popular chlorine sanitizer in granular form. Calcium Hypochlorite has a long shelf life. Cartridge Filter: A filter with a pleated element which traps debris. Resembles a car oil filter. Requires regular cleaning and periodic replacement.

Cedar: Aromatic, attractive wood sometimes used to finish the hot tub exterior cabinet.

Chelating Agent: A chemical which binds up metals. Used to prevent metal staining and water discolorartion.

Chloramines: Odorous organic by-products of ammonia mixing with chlorine. Minimized by showering before entering the tub. Cured by proper shocking or switching to fresh water.

Chlorinator: A canister which releases chlorine or bromine into the water as they dissolve. An in-line chlorinator feeds chlorine through the pool return.

Chlorine: A sanitizer and an oxidizer. As a sanitizier, kills bacteria; as an oxidizer burns off organic matter and kills algae. In the halogen famly. Calcium, lithium, and sodium hypochlorite are some variations. See Cyanuric Acid.

Clarifier: Chemical used to remove haze from water. Particulate matter in suspension needs to clump to be filtered or vacuumed out.

Coagulating Agent: See Flocculating Agent and Clarifier.

Cyanuric Acid: A stabilizing component of some chlorine forms, slows degrading of chlorine by sunlight.

Defoamer: A chemical which reduces and/or eliminates foaming. It pops bubbles. Can be squirted over the water surface. Dichlor: A stabilized form of chlorine.

Digital Programming: Popular controls used to manage such features as water temperature, filtering cycles, light and even accessories such as stereo and TV. Discoloration: Presence of unusual colors in the water, commonly clear green or brown.

Disinfectant: A chemical that kills bacteria and deodorizes. Enzymes: Proteins (formed by cells) that break down oily, odorous, gooey substances and converts them to water and carbon dioxide.

Fiberglass: A material laid up and/or shaped to form hot tub shells. Fiber Optics: Lighting system which has light generated at a remote source. Light is transmitted along fibers.

Filter: A porous, fibrous material in cylinder form that’s called an element. It allows water to pass through while it collects particles, organic matter, oils, lotions and foreign debris that accumulates in hot tub water. Cartridge type element is almost universally employed, though DE – diatomaceous earth – is in rare use.

Filter Cycle: A programmed period of time the hot tub filters water each day. Also refers to the length of time between cleaning or replacing the filter element. Floc or Flocculating Agent: Added to water to coagulate or clump haze causing particles (see Alum or Clarifier).

Flow Monitor: Gauges how fast and how much water is flowing. Flow Rate: The measure of how many gallons per minute pass through a hot tub pump. A better measure of water movement than pump horsepower.

Foam: Frothy bubbles that sometimes form on the hot tub water surface. Also, a polymer-based insulating material sprayed or cemented on the underside of the hot tub shell to slow heat from escaping through the shell. Heat is ALWAYS escaping off the surface of the hot tub water (see insulation).

Free Available Chlorine: The amount of chlorine able to sanitize water that is not tied up in chloramines. Haze: “Cloudiness” in water caused primarily by low sanitizer content, by very small floating particles and/or high pH.

Heater: The method in which hot tub water is warmed electrically. Low pH can attack the heater. Some custom hot tubs have gas heaters.

Humidity: In excess is associated with mildew, especially on indoor hot tubs where moisture tends to be trapped in the hot tub room.

Hydrogen Peroxide: A non-chlorine oxidizer (shock) used with biguanide systems.

Insulation: A polymer-based foam-like material placed between the hot tub shell and the air around the shell essential that works against heat loss, muffles sounds of pump operation, conserves energy and sometimes strengthens the shell.

Intakes: Grated openings in the hot tub shell plumbed to the filter through which water is pulled by the pump(s). Hot tubs without intakes draw water through the skimmer at the surface into the filter system. No pump should be attached to just one suction fitting.

Ionizer: A device that generates copper and/or zinc and/or silver ions to kill bacteria and algae. Jets: The openings through which water flows into the hot tub. Jets affect the direction, volume and velocity of water.

Laminating: A process in which materials with differing properties are layered and bonded to each other to achieve greater strength, lower heat transfer and better sound absorption.

Lighting: Can be arranged around the perimeter, underwater and other various ways to create atmosphere and allow reading in the hot tub.

Lithium Hypochlorite: A stable sanitizer that works at hot tub temperatures. It’s dust-free, has a long shelf life, and lacks strong chlorine odor. Available in dust form.

Main Drain: An exit for water from the hot tub, usually at the lowest point in the hot tub shell. Non-Chlorine Shock: Potassium peroxymonosulfate, an oxygen based shock, that eliminates most chloramines and bromamines.

Organic Matter: Debris such as microorganisms, perspiration, urine and pollen that needs to be burned up or “oxidized” regularly to prevent haze, algae and chloramines.

Oxidizer: Chemical that burns up organic matter. Ozonator: A device used to generate ozone. Assists in disinfection, deodorizing and flocculating.

Ozone: A gas which kills bacteria and assists in purifying water. It is generated and introduced into the hot tub water by an ozonator. pH: Potential hydrogen. A measure of how acidic or base the water is. A pH of 7.0 is neutral. Below 7.0 is acidic. Hot tub water should be kept slightly base (alkaline) with a pH of between 7.2 and 7.6; 7.8 is tops for biguanide. pH Bounce: A wide range of movement of pH levels due to excessive amounts of any added chemical and especially low alkalinity level.

Pillow: Resting places for parts of the anatomy yearning for a soft touch, including the neck, head, back and arms.

Pink Slime: A colorful term used to describe a tenacious algae form (actually bacteria) which rarely shows up in hot tubs using biguanide.

Polyethylene: A plastic used to make some hot tub cabinets.

Polyquat Algaecide: Nonmetallic algae killer. Compatible with mineral systems. Check compatibility with biguanide.

ppm: Parts per million. The same as milligrams per liter, mg/l. A measure of the quantity of a chemical present in hot tub water.

Primary Sanitizer: The essential chemical that kills the negative stuff in hot tubs, i.e. bromine, chlorine and biguanide.

Priming: Starting a flow of water to a pump so it won’t suck air. Pump: Moves water through the filter and heater system and back into the hot tub. Pumps either push or pull water through the filter.

PVC: Polyvinylchloride. A plastic used in piping.

Quats: Quats and polyquats are effective algaecides. Sometimes a cause of foaming.

Redwood: An attractive, durable wood used to cover cabinets.

Residual: Active or inactive chemicals left in water. Salt Water Chlorine

Generator: Makes chlorine from dissolved salt water in the hot tub as it is pumped through an electronic cell and back into the water.

Sand Filter: Uses sand to collect debris from water running through it.

Sanitizer: A chemical used to kill bacteria. Usual generic names are bromine, biguanide and chlorine. Calcium, lithium, and sodium hypochlorite are some options.

Scale: A hard deposit of calcium carbonate which can attach anywhere in or on the hot tub and is damaging to heater effectiveness.

Sequestering Agent: A chemical which bonds with metals to deter staining or discoloration (see Chelating Agent).

Shell: The container which holds both soakers and water. Loosely called the hot tub.

Shock: The action of adding a chemical known as an oxidizer to hot tub water to gas-off organic wastes which cause cloudiness and algae.

Skimmer: A box-like compartment in the hot tub through which debris, oily film and contaminants flow into the filter when the pump is on. Some have a removable basket to collect large debris.

Slurry: A soupy mix of chemicals in hot tub water, usually in a dedicated plastic bucket or watering can.

Soaker: A term describing a person enjoying the benefits of warm, circulating hot tub water.

Stainless Steel: A material which resists staining from minerals. Most grades are impervious to rusting. 316-grade stainless steel is best. Used in many heaters.

Strainer: A basket in some spa pumps that collects debris which could restrict water flow. Super Chlorinate: Using high amounts of chlorine to break down odorous chloramines (see Shock).

TDS: Total dissolved solids. As the name implies, a measure of solids dissolved in and polluting the water. A high level of solids interferes with sanitizing, chemical effectiveness and can cause foam.

Tetraborate Compounds: Alternative clarifiers and algaecides. Total Alkalinity: A measure of the stability of pH. Low total alkalinity causes pH to fluctuate wildly when small amounts of acid or base are added. High total alkalinity makes water more susceptible to scale and high pH, hence cloudy water (see Alkalinity).

Urethane Foam: An insulating plastic used in some hot tubs to protect against heat loss and reinforce the surface to provide support.

Valve: A mechanical means of altering water flow in a pipe. Water Mold: A type of bacteria found in dirty hot tub water. White, gray or pink in color. Very slimy and difficult to eliminate.

Weir: A pivoting flap, door or dam in a skimmer. Prevents bugs and leaves from floating back into the hot tub by collecting them in a basket while allowing water to recycle through the hot tub’s filter system.