We have a pool spa combo . The spa has a main drain with a port on the side. The main drain is capped and it looks like the port on the side of the main drain is also capped ( in the spa) . We bought the house and have never owned a pool so we are not sure how to operate the spa. The spa has its own dedicated pump. We are trying to figure if the current set up is correct. Why would the main drain in the spa have a cap/plug in the bottom and the port on the side also be closed/capped? My husband uncapped the main drain and the pump them filled and seamed to work properly. However the suction is tremendous even with anti vortex drain cover in place. We then replaced the cap in the main drain and figured the port side is what should be uncapped. So the question is... Why would the main drain in the spa be capped in the bottom and at the port on the side of the main drain? Where does the port on the main drain run to?