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Man that stinks!! But it sounds about par for the course for Artesian at least in my experience. I got one of their lemons that did not function properly from day one but I got lucky in that the dealer I got it from stood up and took it back and refunded my money!Good luck and I hope you get it figured out.
Where is it leaking at the pump? Can it not be rebuilt? Is it possible it is just a bad 0-ring or seal to could be replaced? If the motor runs they should be able to make it not leak. There are pumps available online (full retail) so I'm sure the MFG can get them but getting parts can be tricky absolutely. Could you bypass the pump and add a T valve or ball valve that you could open every other week to flow chemicals through it and not go stagnant. Not ideal but at least you are running. Do they have a floor model or another spa in stock they could scavenge the part from? I don't know the whole story but have to say if I sold you the spa I would not leave your house until it was running with or without a replacement pump. I would anonymously calling their (MFG) parts department and see if they will sell you one at their full retail price and see if they bite. If they say sure I've got one sitting on the shelf what's your CC number then you have them in a bind and can raise bloody H e double hockey sticks. If they say sorry out of stock then at least you know you are getting good information and can focus on bandaging it together until it comes in and IMO the dealer needs to step up and get it going stat but again JMO (just my opinion) without all the facts. Unfortunate to hear several poor reviews. They have enjoyed very good reviews for a while now. Will have to keep an eye on them and see if it continues.
This might come in handy... https://docplayer.net/197457857-2019-parts-book-2019-island-spas.html
Good idea about looking for the part myself and then, if I can find it, raising hell with the dealer. Probably a long shot but worth checking.
[The pump could be bypassed with an hour or 2 of plumbing work at most and a couple of dollars ($25) in parts. It could easily be undone when the replacement pump is in.The dealer tech is just taking the easy way out...JMO