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I'd just use the shop vac to get most of the water out, rinse what you can easily rinse, and then fill and go. Any small amount of foaming you may have left over should dissappear, or just use a teeny bit of defoamer to knock it down. I did it! I was able to suck the water out of the precision jets, the foot jets--just about everything, and yes, I was amazed at what came out--almost 5 gallons. Thanks for suggesting that, as I would have had a really hard time using 400 gallons for just a rinse. I like to conserve when I can!Then I rinsed the tub to get any residue off the shell, vacuumed all of that out, and my 400 gallon tub took 70 minutes to fill!