Plumbing is directly related to the jets and jet pumps discussed above and requires its own section due to its importance in hot tub manufacturing. First off, the plumbing length, diameter, and fittings all need to be balanced with the number of jet pumps, size of jet pumps, size of jets, and number of jets. There are many elements here that need to be meticulously considered when designing a hot tub in order to have optimal flow and performance.
Plumbing is also an area in which many hot tub manufacturers trim costs because it is the least visible attribute for discerning buyers because it is hidden behind the hot tub cabinet walls and usually encased in foam insulation.
Most reputable hot tub manufacturers use larger diameter 2-3” flex hoses for their jet pump intake and discharge lines. These larger hoses then connect to individual seats in a hot tub by way of manifolds that split the 2-3” lines into multiple, smaller ports to supply the jets in each seat. A manifold can have between 2-16 ports to supply water to the jets in one particular seat/section in the hot tub. It is very important that these 3” lines going from the jet pump to the jets have as few 90 degree angles as possible to avoid building head pressure since each 90 degree angle can significantly reduce water flow.
Furthermore, it is important to make sure that heavier gauge plumbing (higher schedule rating) is used to avoid cracking and leaking especially if you live in colder climates. Also ensure that the individual jet fittings behind the shell are barbed, glued, and clamped to avoid leaks as jet fittings can be the most difficult to service due to limited access.