Hot Tub/Spa shut-off valve

[Dave Hahn]

Curious whether or not someone can enlighten me about what this shut-off valve under an indoor hot tub/spa would be for, and by default, the tubing its connected to?
The plastic tubing goes off to the right in the first picture and empties into an open floor drain (?) under the tub/spa (in the upper part of the second photo).

I was not inspecting the hot tub/spa, but observed some wetness on the slab underneath through an access portal (which I'll report) and could not determine what this is. Is it possibly a drain valve?

[Jerry Peck]

Looks like the valve is a drain valve and the hose is a drain hose, and that OPEN DRAIN ... should have a grate or something over it, with the hose having an air gap between the hose and the drain.

Is that a floor drain from a shower which had been removed and that tub installed? If not, it looks like the hub end of cast iron, indicating that someone may have removed a vent and are now using it for a drain - which could be far worse than just the open drain from a previous shower.