Manufactures specify that a standard 5/8”x 3/4” water meter will only provide 20 PSI of water pressure. NFPA 13D-Standard for Installation of Sprinkler Systems In One and Two Family Dwellings requires a two head sprinkler design, meaning, your pressure needed to support that system is 26 PSI. A full 3/4″ water meter is needed to properly support the sprinkler demand.