The hot tub manufacturing process can be broken down in to 10 key steps as explained below. Although the process is common from one manufacturer to the next the materials, design, styling, engineering, equipment, features, and especially quality control all vary drastically so it is wise to take a closer look “under the hood” of anything you might consider buying to learn and understand the more granular differences.
- Vacuum-Forming or Thermo-Forming Outer Shell – individual sheets of cast acrylic, available in various sizes and colors, are placed into a large, heated oven (over 300 degrees) until malleable. Then a female hot tub mold is inserted under the heated acrylic and which is then drawn down against the mold following all of the contours until an exact duplicate is created. The newly formed sheet of acrylic is then allowed to cool and is removed from the mold and moved onto the next step.
- Shell Reinforcing – The formed acrylic is flipped over and resin is applied to the back which makes the shell stronger. After then resin is evenly applied then it moves to the fiberglass area where many layers of chopped fiberglass are sprayed onto the resin layer and rolled out. The hand rollers ensure there are no air pockets and that the fiberglass is evenly distributed throughout the back of the shell. This step is one of the most time consuming and costly steps in building a hot tub.
It is important to note that in some manufacturers may use an acrylic sheet that comes pre-reinforced with a layer of ABS plastic that gets thermo-formed in step #1 and therefore skips step #2, however, it is considered a more inferior shell as it doesn’t maintain the same level of structural support.
- Drilling and Cutting – After the fiberglass has cured it is ready for cutting and drilling. Here the holes for the jets, filter, drain, suctions, lights, and topside air & water valves are all cut with exact precision.
- Plumbing– After all of the holes are drilled out then the hot tub is ready for the plumbing step. This step can also be time consuming depending on the number of jets, manifolds, air valves, diverter valves, water features, pumps, filters, etc. that are involved. Furthermore, each fitting typically requires gluing and clamping.
- Framing – After the plumbing step is completed then the hot tub is ready to receive its frame. These days frames are available in wood, steel, or PVC plastic. Frames are typically assembled separately and then attached to the hot tub shell and screwed together.
- Equipment – After the frame is attached then the hot tub is flipped back over (upright) and the equipment gets installed. The equipment typically consists of the spa pack (included heater), topside controllers, pumps/motors, and lighting. Additional equipment such are stereos, upgraded LED lighting, ozone filtration system, salt systems, etc. may also be added.
- Testing – Once the equipment is installed then hot tub is ready for water testing and quality checks. There is usually a designated area with test bays set up and every tub goes thru a water test for up to 24 hours to ensure everything is 100% operational and that there are no leaks.
- Insulation (spray foam) – After the testing and quality inspection is complete then the hot tub is flipped over again and ready to be sprayed with foam insulation. The amount of foam insulation depends on the manufacturer or model. Some units are designed with full foam which mean they fill the tub cavities completely to the cabinet. Some units are designed with a partial foam insulation which means they spray enough to barely cover the plumbing. In either case, they do not foam the equipment side so that they components can breathe and are easily accessible for service.
- Cabinetry and ABS Bottom– In this step the hot tub is flipped over again and the exterior cabinet panels are screwed onto the frame. There are typically four panels (one on each side), however, some manufacturers make the equipment side cabinet panel into three pieces for more manageable access. Also the sealed plastic bottom is stapled on in the step. The ABS plastic bottom makes the tub easier to slide around and also seals it to deter rodents and pests.
- Cleaning and Packaging – This is final step before a spa is loaded onto a truck and shipped to its final destination. Every hot tub goes thru a complete clean-up and detail process before it is wrapped with packaging materials to ensure safe transport.