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This is a factor we looked into when we bought our tub. I told most dealers," I want a tub that comfortable sits 4 adults, and if that means I buy a 6 person tub, then so be it. " My Dynasty, see links associated with my account, is listed as a 6 person tub. We have had 6 people in it comfortably. I wouldn't want to be in it with 5 other guys, but it could hold me and 5 supermodels quite comfortably. Removing suits may save 1/16" per person in space.
Sundance Optima advertized to seat eight, can comfortably seat six, ideally seats four. I've had as many as thirteen in it.Most of the time, the spa is used with one to two people, which I believe is what happens with most spas. I use the spa in a different way than what I had anticipated before I purchased it. If you become a long term regular soaker, it becomes a very personal part of your routine.