It's pretty low; I think the spec says 1/4 of an inch, and that seems about correct. It's just that if you want it bone-dry, you'll need a sponge or something else to dry it. You can also use the drains in the hot tub to drain out the last bits, once the pump has done the bulk of the work. Also, in this particular hot tub, there are some curved seat sections that retain some water, so I used the sponge on those too.
