Hot Tub Manufacturing Process
Most hot tub manufacturers use a similar manufacturing process to build a hot tub as explained step by step below. The process has become best practice, however, each manufacturer adds their own unique technology, components, equipment, and designs along the way to differentiate themselves from the rest.
- Vacuum Forming– Flat, precut sheets of acrylic or thermoplastics are individually placed into a special oven where they are heated to extremely high temperatures and sucked down into molds by vacuums which draw the heated acrylic against the mold contours making a copy of the hot tub mold (each hot tub model has its own mold). Once the acrylic cools off it is then separated from the mold and moved along to the next step in the manufacturing process.
- Fiberglass & Reinforcing– Once the molded acrylic has cooled it is then placed upside down on a rolling platform and enters the fiberglass area. The first step in the fiberglass process is to apply a tacky resin (ie. vinyl ester resin) to the back of the acrylic which helps makes the acrylic mold more rigid and provides a nice surface for the cut fiberglass shards to stick to. The final step is to spray several layers of chopped fiberglass to the back of the acrylic for overall structural support. Once each layer is sprayed on then it must be hand rolled to remove any air pockets and to make ensure there is even distribution.
Fiberglass & Reinforcing
- Drilling – Once the fiberglass shell has hardened and cured it is then moved to the drilling and trimming area. In this step, all of the jet, filter, and suction holes are carefully and precisely drilled out with special tools. Also, all of the edges of the shell are trimmed to make sure they are straight and any excess material is removed.
- Plumbing & Fittings– Once the hot tub drilling is complete then the next stage is to add the plumbing and fittings. This step is a very time consuming one because each jet requires a fitting, glue, and silicone. Also, each jet fitting has two lines plumbed to it. One smaller tube for air and one larger tube for water.Furthermore, all of the individual jet plumbing feed into a manifold and the manifold feeds into a larger 2”-3” flexible PVC waterline. Depending on how many jets a particular hot tub has it can become a very labor intensive step.
Plumbing & Fittings
- Equipment & Framing– Once plumbing is complete the hot tub frame (preassembled) is attached to the fiberglass shell. Frames are typically made of treated wood both for waterproofing and strength. After the frame is attached then the entire hot tub is flipped back over right side up and the equipment is attached.The motors are typically rubber mounted and bolted to the frame and the control box (also referred to as the “spa pack”) is screwed down to the frame. If the hot tub has other components like a 24 hour circulation pump, ozone water purifier, stereo, or LED light box then these are also installed at this time.
Equipment & Framing
- Water Testing & Quality Control – Once the equipment and framing step is completed then you have a working hot tub. At this point in the process most manufacturers have multiple test bays set up for water testing.In a water test station each hot tub is wired and filled with hot water (100-104 degrees) and run for 12-24 hours. During this time a technician checks to make sure that all of the components are receiving power and working properly. The hot tub is also checked for leaks.
- Foaming – If the hot tub passes inspection in the step above then it’s ready to be filled with foam insulation. A thick plastic is wrapped around the frame of the hot tub and the tub shell and plumbing are completely coated with foam. The foam provides not only insulation but rigidity and strength to the plumbing, thereby, eliminating vibration and movement in the plumbing lines which can cause leaks.
- Cabinet– The next to last step is attaching the cabinet to the frame. The cabinet can be made of wood, synthetic wood, or faux stone finish in order to accent any landscape or décor.
- Detail– The last step is detail. In this step the outside of the hot tub is wrapped with a roll of foam to pad and protect the hot tub during freight or shipping. Once the rolled foam is applied then a thick plastic bag is placed over the hot tub and fitted snugly around the spa with a heat gun.