My vacuum head is brand new,it sticks to the bottom of the pool..I do not have a main drain or any valves to close.I only have a skimmer and a Hayward multi port valve..How can I reduce the suction so that I can vacuum my pool?? I have a chlorine dispenser plumbed into the pipes.loosening the cover i thought might reduce suction but,it did not.. What can I do to reduce suction??