When you drain the tub, there’s still water left in the pipes. Any plumbing that’s below the level of your drain will still contain water, and the parts of the tub that are enclosed, such as pumps, can hold water due to air pressure in the lines.
During the winter, that water can freeze and cause hundreds, if not thousands of dollars worth of damage. Depending upon the way your hot tub was designed and installed, that damage may be inaccessible. The best way to avoid a bill for $1500 to repair broken pipes is to invest a few dollars to have your spa winterized by a professional.
Hot Tub manifold, cracked by winter freeze
If a 7 foot long manifold has a small crack, the entire plumbing may have to be rebuilt
