When I had my pool installed a couple years back, the installer didn't put the weir in the skimmer. It wasn't really needed per se because the pool store I bought the pool from recommended leaving the pump running 24x7. They also recommended leaving a tennis ball in the skimmer to break up the vortex that forms from the pump intake so that the pump wouldn't start sucking air. I decided this year to put my pump on a timer, and found out fairly quickly that I needed my weir in my skimmer to keep all of the **** in the skimmer basket from floating back out into the pool when the pump kicks off; however, I've noticed that the tennis ball sometimes gets underneath the weir when the pump's running. So, do I still need the tennis ball to break up the vortex, or will the water flow over the weir do that for me??