1. The suction lines could be clogged.
  2. The valves could be set in the “off” position.

The problem of low pressure is usually a clogged pump basket (the basket connected to the pool pump) or skimmer baskets full of leaves. Clogged baskets restrict the flow of water into the filter, which causes low pressure. A clogged impeller (blade inside the pump) can also cause low pressure. This should not happen if your pump basket is kept free of debris and in good condition. If you have a suction type cleaner and have this problem often try adding an in-line leaf catcher between your first and second hoses from the wall.

There might even be a need for a PRESSURE TYPE cleaner if you have an over abundance of leaves.

Clogged Skimmer Basket