Master Spa Twilight leak

[FriedChicken]

Hello Everyone.
This is my first post but I have learned a lot as of late as I have recently moved into a new home with an existing spa so trying to figure things out as I go along.
My issue is I’ve noticed my spa has a leak. After some digging, I found it was coming from the white hose in the top of the picture. It has a rubber gasket inside.Does anyone know what this hose is for?
What is it attached to?
Can I plug it without any adverse effects?
Thanks for your help in advance.

 

[ajw22]

Welcome to TFP.

Let's see if @RDspaguy knows what is going on with that leak.

It looks to me like an air intake and I don't know what would get water backflowing out of it.

 

[RDspaguy]

That is a check valve, likely for an air intake as mentioned. You can replace it, but under normal operation it should not have water in it.
Overfilling can cause water to get there when the jets are off, but should stop leaking when the jets are on and air control valves are open. Water level should be at least 3" below the top edge of the spa.
If it is leaking only when the jets are on you have another, bigger issue.

 

[FriedChicken]

Thanks ajw22 and RDspaguy for your responses. I wanted to give you an update.
I did a lot of research once I found out what that hose was (thanks again for that info) and it lead me to check my jets for a leak. As it turns out one of the four neck massage jets on top was not installed properly after cleaning. I have since my previous response drained my tub to fix the motor for my jets 2. It was humming but no longer pushing water. Pulled it from the tub. Turned out to be a bad capacitor. I ordered a replacement along with some Ahhhsome to thoroughly clean out the tub since I was draining it anyway. I’m doing some deck work as well so I’ll keep you posted once it’s all up and running.