Leak at the spa overflow

[Poolster1]

Hi Pool novice here - the house came with pool/spa combo (probably built 30 years ago).
We found water leaking from around the overflow line from the Spa. Not sure if it is a break in the PVC or via water seeping into gap between the PVC and the stucco. Trying to silicone seal around the PVC opening... but also wondering what the purpose of this overflow is. We do have a spillway that will overflow the spa water back into the pool. This overflow port is at about the same height and gets covered with water when spillway is flowing. Question is: If the silicone sealant is not able to fix this leak, can I just plug this port with a rubber plug? Why do I need this when the overflow goes in to the pool via spillway?

 

[ajw22]

Welcome to TFP.

I see no reason for an overflow line in a spa that has a spillover.

Only reason I can think of is if the pool is covered and the spillover blocked in the winter while the spa is left open for use.

Where does the overflow line drain to?

 

[Poolster1]

Thanks @ajw22 - I am not sure where it drains to as it disappears under some hardscape. We've been noticing a lot of moisture underneath the house and ground saturation, and I think this constant leak could've be a contributor. I'm inclined to just plug it with some rubber stopper from the spa side, and see if we can prevent the constant seepage.