Aquacera 9" CeraMetix Ceramic/Fluoride Filter For Gravity Filters 4 Pack Maximum working pressure: 25 psi (8.6 bars) Maximum working Temperature: 100 F (37.8 C) Minimum working temperature: 40 F (4.4 C) Recommended change frequency every 12 months Recommended cleaning frequency: every 6 months or when flow rate is noticeably lower