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Looks to be about 1 and 3/8 inches difference give or take a smidge over the 8 foot area I intend to put the tub. Likely to be a major issue?
That shouldn't be a problem but I know you may be a bit annoyed by it. What is key is if you can align the spa so the high water side is set up with the side of the spa that has the highest jets and the low water side with the jets that aren't so high (often there are variations in the height of the jets from one side to the other). Take the time to look closer at the spa at the dealer and plan it out.
Have you looked into getting the slab mud jacked? My neighbor had this done on some concrete that settled. They drilled holes in the concrete and pumped in some type of cement, lifting the slab. Not sure how much it costs, but it might be worth looking into.
Unfortunately this a concrete pad that is 380 square feet and not just a slab for the tub itself. It is under my deck and the posts for the deck go thru the pad onto footings. Hasn't really settled, I expect it was slanted a bit to run water off it. I just didn't plan far enough in advance to have them not slant at least part of it for a future tub. Trying to raise only a portion of it may result in a lot of cracking and don't know how it might impact the deck above. I guess I need to take a few pictures to post. I've been meaning to do that anyway!
What I've seen done a few times that works well is to make a simple open box frame (slightly larger than the fotprint of the spa pedestal) with PT 2x4s set upright but you rip the 2x4s so that the top of the frame is level on the pad. You then fill the frame with pea gravel and set the spa on teh level gravel and you ahve a level spa. Works well and lasts a long time.
I wouldn't worry about it too much, as others have said as long as the water is covering the jets that is should and also importantly is getting into the filters as it should.Another solution would be to build a deck ontop of the pad. My buddy did this for his porch. He had a cement porch that was cracked and uneven so he built a deck on top of it. The hard part is cutting the joists to the right angles so the tops of them are sitting level. In your case if your pad is not cracked it souldn't be that hard. Just take your 1 3/8th's at the one end and draw a line to the top of the other and there is your angle to cut. That is if you are worried about it. If the fram of the tub sits level and is supported I would say its good. My tub is not perfectly level either. my low side is the filter side. I am out about 1 " over a 12' deck. Good luck
Thanks. I plan to go by the dealer as well today or tomorrow just to get there impression. Would prefer not to do anything and if they also feel it is no big deal I probably will. But it will no doubt bug me and fixing it now is no doubt easier than fixing it later! :-/