The level at which the swimming pool skimmers operate best is betweenone third and one half the way up the opening of the pool skimmer. If the levelis higher, the water moving into the skimmer is going so slow that debris maypass by the opening without being pulled in. If the pool water is so high thatit covers the skimmer opening, floating debris can't get in. If the water istoo low the skimmer can bottom out, thereby sucking air into the system whichcan result in losing the prime and possibly result in burning up your swim poolfilter pump motor. Add water before back washing and vacuuming the pool becausethis will also lower the water level.