First time poster and second season pool owner. I have a 20x30 in ground pool with attached spa. Just had the pool opened last week. I turned on the air blower for the spa and there are no bubbles coming into the spa (normally it resembles a rapid boil). I can hear the blower motor, so I know that is functioning. I can feel some water coming through the jets but no air or bubbles. The valve is turned to the on position. Is there a plug or something close to the blower motor that could have been over looked during opening? The spa heats just fine, just no bubbles. I've seen some mention of check valves. Any suggestions or advice are greatly appreciated. Thank you.