hi i am replacing my bottom entry ball valve with a torbeck valve this has two flow restrictors supplied with it high pressure and low it gives three choices low high or no restrictor it gives water pressure psi ie below 14psi no rstrictor 14 to 60 psi lp restrictor over 60 psi hp restrictor how do you establish which one to fit. the toilet cystern is suppied with mains pressure thanks kris.