I used to install a bunch of in-ground spas back in my youth. At this point I can't recommend a stand-alone concrete spa. The best portable spas are just better in every way. Always clean, always at desired temp, jet options beyond belief, and much more comfortable seating. If you want it to be a focal point in the backyard that you might use occasionally, an in-ground still may make sense. If you want ease of ownership and more Porsche than GMC experience, take a good look at Hot Spring, Caldera, and Sundance spas. You can still build them into a deck and get an in-ground look with all the benefits of fully self contained.
No current affiliation but I owned a spa dealership for 20 years:
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