A Guide To Things You Should Know If You Are Buying A Hot Tub

people in hot tub in snow

Hot tubbing in the snow.  Chris Clinton/Getty Images

Words and Terms To Know if You Own a Spa or Hot Tub

Isn’t it about time you got to know your hot tub better? Owning a spa means you’ll need to know the words and terms that accompany it, whether you maintain the tub yourself or hire a professional.

Welcome to the World of Spas and Hot Tubs

hot tub with view

A hot tub with a view. Kelly Funk/Getty Images

Consult this handy glossary as a quick reference tool. If a word or term is missing, contact us on social media and it will be added.


A dry or liquid chemical that lowers pH when added to water.

Air Switch

A pneumatic-mechanical control devce that is used to safely operate spa and hot tub equipment. To operate, a button that is located in or near the water is depressed, sending air pressure along a hose to an on/off switch.


The characteristic of water tht registers a pH above neutral.

Aluminium Sulphate

An additive for sand filters that helps prevent sand from combining and hardening; thus, not filtering impurities from water.


Any person using a spa or hot tub. Hopefully, not to take an actual bath with soap and shampoo, but for relaxation or as hydrotherapy.


A sanitizer similar to chlorine and one of the original hot tub sanitizers.


A sanitizer which is part of a water treatment system.


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

Digital Programming

Popular controls used to manage such features as water temperature, filtering cycles, light and even accessories such as stereo and TV.


A material shaped to form hot tub shells.

Fibre Optics

Lighting system in which light is generated at a remote source and transmitted along fibres.


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.

    • What is a Sand Filter? This predominantly for commercial hot tubs and pools – jump to ‘What is a Cartridge Filter to continue for hot tubs.

Pool Equipment: Getting to Know the Parts of Your Swimming Pool

How intimately do you know your swimming pool? If you maintain it yourself—even part-time—then you should know about some of the inner-workings of that big body of water in your garden. Let us help you take the mystery out of some of the main components of your swimming pool, so at least if the pool repair person is explaining something, you won’t have a spacey, far-off look in your eyes as he/she uses terms like surface skimmer and filtration system.

Pool equipment and parts are listed in alphabetical order.

What is Backwashing?

 OK: you can’t go to a pool supply store and ask to buy a backwasher. They might know what you’re talking about, but you’ll give away that you don’t know the correct terms for the parts of your pool. Whether you buy your pool equipment from a local retailer or shop online, this is an important word to know for general pool maintenance.

backwashing pool

 Beatrice Murch/Flickr/CC BY-SA 2.0 

Backwash or backwashing is the process of thoroughly cleaning a swimming pool’s filter by a method of reversing the flow of water to flush out contaminants. This way, you don’t have to clean the filter manually, and it usually takes just a few minutes. Continue the process until the water runs clear through the waste line.

You’ll know that it’s time to perform the backwashing routine when the pressure gauge indicates a pressure rise of 8-10 pounds above the clean or “startup” pressure.

Dirt Passing Back into Pool 

If dirt or DE (diatomaceous earth) gets through the filter and into the pool, check for:

    • Damaged grids, laterals or cartridges
    • Broken manifolds or retainers
    • Backwash valves that have bad gaskets or O-rings

Maintenance and prevention are key: when you feel a backwash valve becoming difficult to turn, do a teardown and lubricate before any leaks occur. While you’re at it, carefully examine grids, laterals, cartridges, and manifolds each time you break down a filter for cleaning. Don’t be in a rush when reassembling—sloppy and careless reassembly after cleaning is the cause of most filter leaks.

Filters and Backwashing 

While each type of filter will keep your pool clean, the key to keeping it that way is by making sure the filter is the correct size and is regularly cleaned. So, what’s the best type of filter? The one you’re most likely to keep clean. Cartridge filters are often a popular choice because they are easy to maintain. Choose the filter that fits the size of your pool.

Backwashing a DE filter should be considered a temporary solution when a complete teardown and cleaning aren’t practical. A sand filter works well with backwashing. Since there is no DE to add, it removes the potential for errors that may result in a dirty pool.

How to Backwash a Filter 

Instructions vary according to your filter type; it’s best to consult the website of the filter manufacturer, if possible. Basically, this is how it is done with a DE filter:

  1. Turn off the pump and turn the backwash valve (plunger or multivalve) to the backwash setting.
  2. Turn on the pump again until the filter view-glass appears clear. Try to alternate between backwash and rinse (or filter for plungers) a few times to remove more DE. Don’t forget to turn off the pump when changing valve settings.
  3. Discard the DE in the garden or in the trash. Some units include a DE separation tank that captures and contains the DE.
  4. Turn off the pump to make sure that the timer or automation system doesn’t turn back on while the filter is being disassembled.
  5. Drain the filter by opening the release valve at the top of the filter to allow the water to drain. For thorough draining, remove the drain plug (sometimes by using a screwdriver) at the bottom of the filter so the water can drain from the tank’s bottom.

How Often Should You Backwash? 

Backwashing and teardown depend on how often you use your swimming pool and just how dirty it actually gets with normal use. DE filters are usually torn down and cleaned at least six times per year. Unless your pool gets really dirty, you should not need to backwash it beyond your scheduled maintenance.

Another theory recommends to backwash when the pressure gauge is about 8 to 10 psi (pound-force per square inch) over the starting level. Also, backwash if a major storm or weather event has occurred in your region or a there is a major algae outbreak (any colour).

Sand filters, however, can be backwashed once a month and are typically torn down two times per year. To backwash a sand filter:

  1. Shut off the system 
  2. Clamp the backwash hose to the water outlet
  3. Position the backwash valve to either push or pull—the water will flow through the hose or the equipment
  4. Turn the handle to the backwashing position
  5. Backwash for a few minutes or until the water clears
  6. Turn off the system to stop the backwashing process
  7. Roll up the hose
  8. Move the valve handle to its previous position, which will permit water to flow through the system. Lock it in place
  9. While turning on the system, open the air relief valve, which is located at the top of the filter. Leave it open until water flows through
  10. Close the valve and shut off the system

Saving Energy 

You can save energy by running the pump at a lower speed after cleaning the filter. This can be achieved without reaching a point of no-flow or low-flow.

Cartridge Filter

This type of filter for your pool is gaining in popularity, probably because it’s safe, effective, convenient and does not need any backwashing or disposal.

Centrifugal Pump

Learn how a centrifugal pump works by doing this Basic Science 101 project. Involve your kids — it’s fun!


Without coping, the steel projecting from the pool’s walls would be exposed and water could get behind the pool shell. Discover other functions of pool coping.

DE Filter

Not surprisingly, DE, aka diatomaceous earth, is the main ingredient in a DE pool filter. Discover why many pool owners consider DE filters to be the best kind of pool filter.

Gas Heater

While solar has been grabbing all the attention, gas heaters still account for most of the heaters in residential pools. Discover why they are still a good idea for heating small pools and spas.

Main Drain

In most residential pools, two main drains are located at the bottom — the deepest part of the swimming pool. Discover which one the main drain is and its primary purpose.

Pumps and Motors

Working in tandem with the motor, the pool pump draws water from a pool or spa and somehow returns it back to the pool or spa. Find out how this happens and why it’s an integral part of your pool.

Sand Filter

 What? Another type of filter for your pool? Too many choices. Learn the pros and cons of this type and why it might be the right type for your particular swimming pool.


Most residential pools have skimmers, which help with debris collection. Find out the other functions of a skimmer and the types of debris it collects (ick alert!).


Weirs are best friends to skimmers and you rarely see one without the other.


    • What is a Cartridge Filter?
    • A disposable paper cylinder used to capture gunk and boogies floating in the water – discharged from bathers. They vary in size, design, quality and location within the spa/pool. The more efficient the filter – the less chemicals you will need and the longer the water lasts before emptying is required

Filter Cycle

A programmed period of time the hot tub filters water each day. Also refers to the length of time between cleaning and replacing the filter element.

Flow Switch/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.


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.


The method by which hot tub water is warmed electrically. Some custom hot tubs have gas heaters.


Pertaining to hot tubs and spas: the external use of warm or hot water to treat diseases and ailment. Hydrotherapy is used for conditions ranging from stress to sore or strained muscles and arthritis. Jets that move the water, along with the warmth, help in treatment.


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.


The openings through which water flows into the hot tub. Jets affect the direction, volume and velocity of water.


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

Main Drain

An exit for water from the hot tub, usually at the lowest point in the hot tub shell.


A device that assists in disinfection.

pH or 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.


A plastic used to make some hot tub cabinets.


Parts per million.  A measure of the quantity of a chemical present in hot tub water.


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.


A dry or liquid chemical that has been formulated for water testing. An agent or substance that reacts to another known agent, producing a predictable color.

Sand Filter

A filter that uses sand to collect debris from water running through it.


A chemical compound that oxidizes organic material and bacteria to provide a clean, bacteria-free water environment.


The container of a hot tub or spa that holds water and bathers or soakers.

Shock Treatment

Also known as: Super-Chlorination or shocking

Application of extremely high levels of chlorine to completely oxidize any organic material in a hot tub or spa and leave a substantial chlorine residual. This procedure is performed to sanitize elements in water that might resist normal chlorination.


A part of the circulation system that removes debris from the surface of the spa water by drawing surface water through it.

What is a Pool or Spa Skimmer Used For?

Swimming Pool Parts and Maintenance

robotic pool skimmer

A robotic pool skimmer in a swimming pool.  Flickr member Wicker Paradise 

Think of a pool skimmer in a residential swimming pool like you would a gutter in a larger public swimming pool: it helps to clean by skimming water and capturing floating debris such as leaves, flower petals, dirt, twigs, dead insects, and oil (sunblock)― before the waste can sink to the pool’s bottom.

Most skimmers on in-ground pools are built into its upper sides, where the suction draws debris and traps it. Most pool skimmers are accessed via the pool deck area through a trap door or hatch. The skimmer is also in a convenient location to attach a suction line for a pool vacuum.

Skimmers for In-Ground Pools 

A surface skimmer is typically made of plastic (or PVC) or precast concrete and has a tank with a projecting throat on its upper side. The skimming action is performed by the weir, which regulates the amount of water entering the skimmer. Since the weird adjusts to permit only a thin layer of water to spill over, water is pulled off the surface quickly―keeping a large part of the pool surface clear.

One skimmer that is positioned in a good location can keep about 500 square feet of its surface clean. If the debris gathered by the skimmer is left to accumulate, it can put additional strain on the pump. For this reason, among others, the skimmer basket should be cleaned out daily during swim season.

A skimmer must be installed with an equalizer line, which is a pipe that connects from the bottom of the skimmer basket through the pool wall and into the water. The equalizer helps to prevent air from being sucked into the system if evaporation causes the water level to drop below the weir level. Make sure air doesn’t enter the system―it could cause the pump to stall.

Many pool skimmers come equipped with automatic water level controls and automatic chlorinators.

Robotic Pool Skimmers 

In recent years, floating and robotic pool skimmers have entered the market and offer an alternative to a stationary model. Operated by batteries or solar power, these automatic skimmers float on the surface of a pool, collecting debris as it moves through the pool. Devotees of products like the Solar Breeze NX claim it cuts down on time and work, especially in areas prone to winds carrying leaves and debris into the pool or regions with lots of insects. It can also lower the cost of energy bills, as it is designed to work independently of the pool pump.

Other automatic skimmers, like the whirlpool-like the SkimmerMotion, is designed to connect to an automatic pool cleaner (vacuum), then collects surface debris as it floats through the pool. Debris is sent to the pool’s filtration system.

Adding Chlorine Tablets to a Skimmer 

While some pool owners claim that placing those chlorine tablets―known as hockey or chlorine pucks–right in the skimmer basket cuts down on time, many pros advised against this. The high concentration of acid can break down parts of the filter, possibly causing a need for more frequent replacement.

Above-Ground Skimmers

Because above-ground pools have thin walls, floating pool skimmers are most often used, as are units that hang on the pool’s edge. To keep skimmers for above- and in-ground pools working properly, try to clean out the skimmer basket daily during swim season.

Skimmers for Spas and Hot Tubs

Skimmers for redwood hot tubs usually have no basket; instead, skimming the surface and pulling debris to a plastic screen. Some portable spas have skimmers with built-in cartridge filters. 


A person who is soaking in the spa or hot tub, presumably to reap the benefits of the hot water and circulation. See bather.

Stainless Steel

A material used in building hot tubs and spas that is resistant to staining from minerals. Most grades resist rusting.

Strainer Basket

A plastic mesh container that strains debris from water flowing through it inside the strainer pot.

Temperature, Ambient

The average surrounding temperature.


Part of the heater control circuit. Adjustable, this device senses temperature and can be set to break the circuit when a certain temperature is reached. It then closes the circuit when the temperature falls below that level.

Time Clock

Aka timer: An electromechanical device that automatically turns something on or off at preset intervals.

Total Alkalinity

A measure of the stability of pH.

Urethane Foam

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


A plumbing device that controls the flow of water.


A barrier in a skimmer over which water flows. The floating type raises and lowers its level to match the water level in the spa, while another type floats up and down inside the skimmer basket.

    • What is a Weir?

Now that you know all the right words in the world of spas, you’ll be able to impress friends next time you’re soaking in the hot tub together. Even better: you’ll understand what the terms are while reading up on your spa.

How Pool Weirs Work With a Skimmer

A weir is a type of barrier across a river that is created to adjust or alter its flow. With this in mind, a weir for a swimming pool is a barrier in a skimmer over which water flows. A floating weir raises and lowers its level to match the water level in a pool or spa. Another type is shaped like a barrel and floats up and down inside the skimmer basket. 

Understanding a Pool’s Basic Plumbing System

To help you troubleshoot any problems that might arise with your swimming pool, it helps to have a basic understanding of how your pool works. In this case, it’s the pool’s plumbing system. Water enters a pool through the main drain, a skimmer, or both. It journeys to a three-port valve and into the pump, which is run by an attached motor. From there, the water travels through a filter, then up to solar panels or to the heater (if they are installed) and back through the valves to the pool return lines.

Enter the Skimmer

This is where the skimmer comes in. Some pools have more than one. A skimmer’s primary function is to pull water into the system with a skimming action, which means it pulls in dirt, oil, leaves, twigs, and debris hopefully before they can fall to the bottom of the pool. A skimmer also provides a conveniently located suction line for vacuuming.

Many pool circulating systems have at least two surface skimmers connected to the pump. While most skimmers are built into the pool, some types are designed to hang on the side. Most are molded, one-piece plastic units. Older pools often have built-in-place concrete skimmers. For the most effective collection of debris, there should be one skimmer for approximately every 500 square feet of pool surface.

Newer models include floating automatic or robotic skimmers, some of which are solar powered. This kind of skimmer connects to an automatic pool cleaner(vacuum), while the solar model floats independently along the surface of the pool, collecting all types of debris. Both models are designed to keep a pool cleaner, cut down on your time and energy spent maintaining the pool, and save money and energy by not putting so much strain on the pump.

The Skimmer and the Weir

Most skimmers consist of a tank with a projecting throat-like device on its upper side. There, a self-adjusting weir (or floating weir) performs the skimming action by regulating the amount of water that enters the skimmer. Because it adjusts to allow only a thin sheet of water to spill over, velocity, not volume, is the key to good skimming action. It must have an equalizer line—a pipe that extends from the bottom of the skimmer about 12 to 18 inches through the pool wall into the water—to prevent air from being sucked into the system when the water level is low. Skimmers work best when located on the “downwind” side of the pool; the wind helps push debris toward its opening.

Water pours over a floating weir that allows debris to enter. When the pump is shut off and the suction stops, the weir floats into a vertical position, which prevents debris from floating back into the pool. Some skimmers don’t have this type of weir and use a floating barrel as part of the skimmer basket. The basket collects leaves and larger pieces of debris, allowing you to remove them easily. 

Replacing a Weir

Luckily, a weir is a fairly easy part to replace. With a pair of pliers, remove the old or damaged weir from the skimmer and insert the replacement in the same position by pulling out its pins. A spring should release retaining rods that push against the skimmer walls. Popular brands include:

    • Pentair
    • Blue Devil
    • Waterways

By Lisa Hallett Taylor