How Hot Tubs Work: A Comprehensive Guide


In this comprehensive guide, we will delve deep into the inner workings of hot tubs. Hot tubs, often associated with relaxation and hydrotherapy, have become increasingly popular for their soothing effects on both the body and mind. Whether you are a prospective buyer or simply curious about the technology behind these comforting havens, understanding how hot tubs work is essential.

Exploring the Anatomy of a Hot Tub

1. Pool of Water and Shell Material

Hot tubs consist of a pool of water, usually above ground, contained within a durable shell. The most commonly used materials for these shells are fiberglass, acrylic, or plastic. This shell, carefully designed to support the weight of the water and the occupants, forms the foundation of the hot tub.

2. Heating System

The heart of any hot tub is its heating system, responsible for elevating the water temperature to the desired level. There are two primary types of heating systems: electric heaters and gas burners. Electric hot tubs utilize electricity to heat the water, while traditional hot tubs rely on propane or other flammable gases. Some enthusiasts even opt for wood-fired hot tubs, making use of wood as a natural fuel source.

3. Circulation Pump

To create water pressure for heating and jet nozzles, hot tubs are equipped with a circulation pump. This component plays a crucial role in the hot tub maintenance by maintaining a consistent flow of water within the system, ensuring that the water is evenly heated and circulated for an enjoyable experience.

4. Hot Tub Filters

Hot tub filters are essential for maintaining water cleanliness. They work tirelessly to remove impurities and debris from the circulating water. The most commonly used filters are paper cartridge filters, which require regular cleaning and occasional replacement for optimal filtration.

The Art of Crafting Hot Tubs

1. Construction Materials

The construction of hot tubs typically begins with raw materials such as plastic, steel, and fiberglass. Most modern hot tubs are constructed using fiberglass and acrylic or plastic shells, supported by a sturdy steel structure. The acrylic shell is vacuum molded and reinforced with fiberglass before being assembled onto the support structure. This intricate process requires skilled craftsmanship to produce high-quality hot tubs.

2. Cabinet Components

The choice of cabinet components depends on consumer preferences. Mass-manufactured hot tubs often feature cabinets made from acrylic or plastic, reinforced with fiberglass, and supported by a steel structure. The plumbing in these hot tubs consists of copper tubes, and the heating and filtration systems are typically crafted from steel, aluminum, or titanium.

3. Custom Hot Tub Creation

For those seeking a unique experience, crafting custom hot tubs is an option. Customization allows for the use of various materials, such as wood shells reinforced with steel or aluminum bands. Some fortunate individuals even have the opportunity to build hot tubs near natural hot springs, creating an eco-friendly and self-sustaining oasis.

Understanding Hot Tub Control Systems

Hot tub control systems are distinct from those found in standard pools. Most hot tubs feature two primary controls: temperature and flow rate. Newer models may include additional controls for features like bubbles, lights, and music.

1. Topside Controls

Topside controls are conveniently located within the hot tub’s body and are accessible while using the large tub or spa. These controls are the most common in modern hot tubs, allowing users to adjust settings effortlessly.

2. Spa-Side Controls

Spa hot tub works on-side controls, an alternative design, are typically located near the hot tub’s pumps and heating element. These controls serve the same functions and often come with remote control options. High-end systems may integrate the remote control seamlessly into the hot tub’s design during installation.

Plumbing Systems in Hot Tubs

Hot tub plumbing consists of three main components: circulation, filtration, and heating. These components operate within the hot tub plumbing work as a closed system, ensuring that the water remains within the hot tub except for natural evaporation.

1. Circulation

Circulation of warm water is crucial for maintaining water cleanliness and preventing bacterial growth. Circulators use gravity to move water from one side of the hot tub to another, eliminating the need for additional pumps.

2. Filtration

Filtration is responsible for removing impurities from the water. Most hot tubs employ paper cartridge filters, which require regular rinsing and occasional replacement to ensure optimal filtration.

3. Heating Systems

Hot tub heaters maintain the water at a consistent temperature, providing a comfortable and therapeutic experience. Heating methods for hot water can vary, with options including electric heaters, convection heaters, or solar panels.

The Journey of Water within a Hot Tub

To better illustrate the flow of water within a hot tub, let’s explore the key components in more detail:

Suction Line

The suction line is attached to the pump and draws water from the hot tub through the skimmer filter and floor drain. These water sources combine into a single line that enters the pump, initiating the water’s journey through the system.


The pump plays a pivotal role by drawing hot tub water from the suction line and directing it through the filter, heater, and back into the water jet array. The pump’s power is important, with reputable hot tubs typically featuring one pump per 20-30 water jets, to ensure adequate water flow.


After passing through the pump, the water flows through the filter. Cartridge filters, known for their ease low speed of replacement, are the most commonly used filter type. These filters collect bacteria, pollutants, and debris, making filter maintenance a critical aspect of hot tub ownership.


Following filtration, the water enters the heating coil, where it comes into contact with a hot heating element. The heating method, whether electric, gas, or wood-fired, determines the speed at which the water is heated.

Ozonator (Optional)

Some hot tubs and swimming pools are equipped with ozonators to enhance water cleanliness. Ozonators generate ozone gas and inject it into the water, effectively removing pollutants through oxidation. There are two primary types: ultraviolet (UV) and corona discharge (CD) ozonators, with CD ozonators being more widely used due to their efficiency and durability.

Return Line

The return line marks the end of the whole filtration system process, reconnecting the heated water with the hot tub’s manifold system.


Manifolds serve as distribution points to circulate water around, splitting the returning water flow into streams for each jet or nozzle in the hot tub. The size of the manifolds varies depending on the hot tub’s design and the number of jets and nozzles.

PVC Tubes

Plastic or PVC tubes connect the manifolds to the individual nozzles, guiding the water flow to its designated output points. These tubes are designed to be flexible and durable, ensuring a high speed and smooth flow without strain on the plumbing.

Jets or Hydro Jets

Jets or nozzles play a crucial role in creating the soothing water massage effect. They typically consist of three parts: a water inlet, an air inlet for generating bubbles, and an output nozzle. Many jets feature adjustable flow control systems to customize the massage experience.

By gaining a comprehensive understanding of how hot tubs work, you are better equipped to make informed decisions when purchasing, maintaining, or doing hot tub work or simply enjoying these relaxing aquatic marvels. Hot tubs offer a haven of relaxation and rejuvenation, and now, you have the knowledge to fully appreciate their inner workings.


  • Jason

    Jason is an experienced writer, having contributed to many popular websites over the years. He currently writes for Big Hot Tub, a blog about everything hot tubs. When he's not writing or working on his blog, Jason enjoys spending time with his wife and two young children.