How Does a Hot Tub Work?

How Does a Hot Tub Work?

Hot tubs and spas provide immense benefits, whether unwinding after a grueling day at work or adding a touch of fun to your BBQ party. But have you ever paused to wonder how these machines operate? How hot tubs function is fascinating, and understanding the inner workings can benefit you in several ways. It allows you to make informed comparisons when purchasing, manage potential maintenance issues, and use your hot tub or spa more cost-effectively. 

So, let's dive right in and uncover the secrets of the hot tub. 

What is a Hot Tub?

A hot tub is a pool with distinct features designed to deliver a therapeutic soak powered by electricity or gas. They are typically above ground and contained in a fiberglass shell. Here are the main components: 

  • A pool of water 
  • Hot water heating system, powered by electricity or gas 
  • Circulation pump for water pressure 
  • Hot tub filters for clean water 

Hot tubs and spas come in various sizes, from the intimate single-seater to the grandeur of a tub that can accommodate 6-8 people. 

How are Hot Tubs Made?

The most common method to construct hot tubs begins with raw materials like plastic, steel, and fiberglass. Modern hot tubs feature an acrylic or plastic shell reinforced with fiberglass, placed over a steel structure for support. The shell is assembled, adding components like the pump, filter, control panel, and jets. This process requires skill and expertise to ensure high-quality results. 

What are Hot Tubs Made From?

Your choice determines the components of the cabinet. Mass-manufactured hot tubs are generally comprised of acrylic or plastic, reinforced with fiberglass, supported by steel, plumbed with copper tubes, and powered by steel, aluminum, or titanium heating and filtration systems. 

How Does a Hot Tub Control System Work?

Hot tub control systems regulate temperature and flow rate, and in newer models, functions such as bubbles, lights, and music. There are two main types of controls: 

  • Topside controls within the hot tub's body are the most common in modern hot tubs 
  • Spa-side controls near the hot tub pumps and heating element usually come with a remote control 

How Does the Hot Tub Plumbing Work?

A hot tub's plumbing includes three main parts: circulation, filtration, and heating. It's a closed system, meaning the water never leaves the system except for evaporation. 

  • Circulation keeps the water clean and prevents bacteria growth. 
  • Filtration removes impurities from the water. Cartridge filters are the most common, which need to be rinsed, cleaned, and replaced periodically. 
  • Heating Systems maintain the water at a comfortable temperature. Spas may use electric heaters, convection heaters, or solar panels. 

The Journey of Water Through a Hot Tub System

The water's journey starts from the suction line attached to the pump, which draws water from the hot tub. The pump sends this water through the filter, which traps bacteria, pollutants, and debris. Post-filtration, the water travels to the heater, which heats it up and then returns it to the tub. 

Some spas utilize ozone generators positioned after the heater in the equipment cycle, which generate ozone gas to oxidize pollutants, thereby reducing chemical usage. 

Finally, the water returns to the tub through the return line, which connects the heater to the manifolds. The manifolds split the returning flow into streams for each jet, directing it through PVC tubes to the nozzles. 

Understanding the Nozzles

Each jet or nozzle of a hot tub has three parts: 

  • Water In – The connection to the filtration system 
  • Air In – A small hole in the jet creates bubbles, known as the Venturi effect 
  • Output Nozzle – Sends the bubbly water into the hot tub 

Most jets have a twist control system to adjust the flow speed individually. 


Now that you understand the inner workings of a hot tub and spa, you are better equipped to choose the best one for your home. Understanding the components and how they operate can help you select a model that meets your needs and preferences. The key is to make an informed decision so you can enjoy the benefits of a hot tub for years to come.