FJMeans

I just bought a house with an in ground pool and spa combo. This my first time owning either. There is a small (1 1/2" - 2") pipe in the wall in between the two, which allows water flow (I assume). The pool is much colder than the spa. As I am attempting to heat up the spa, cold water from the pool just keeps rising in through that tube. I'd like my spa to operate between 100-103 degrees, but I cannot seem to get it past the low 90's with the cold (70-72 degree) pool water flowing in. The NG heater keeps running (set to max temp) without the ability to reach the desired temp in the spa. Is that pipe supposed to be there, is there supposed to be a cap... I'm freaking out... PLEASE HELP!! Thanks!