I have an older pool that has an attached spa (originally built in early 1980s...new plumbing in 2013).
I had the pool company close the pool that did the re-plumb and renovation.
When they closed the spa, they simply blew air through the line and closed the valve to create an airlock (like one closes the main drain in the pool).
My question is, since the spa is very easy to completely drain and simply close in the floor drain itself with a plug, why take this risk? It would seem to me the spa (hardly being below ground level) could freeze entirely and if the air lock/seal breaks theres a serious problem.
Apparently the pool company warrants the lines if they break in winter, put the risk is huge: breaking up a brand new poured concrete deck for one.
Would appreciate thoughts on this.