im new at this spa stuff so i will try to explain as much as poss.i had a spa given to me and its a 1985 hydro tube spa and there is a gray valve on the side of it that is for the blower to hook up to. (i think.) is this supposed to be a one way check valve so the air will blow one way or will the water come back thru it. here is a pic ot the tub and the valve. http://f1.pg.photos.yahoo.com/ph/autococker1232000/album?.dir=/2404&.src=ph&store=&prodid=&.done=http%3a//photos.yahoo.com/ph//my_photos

sounds like a ortega valve which simply when turned , sends water to different jets .
Have you tried turning it while the jet pump is on to see what jets it is controlling?