{"product_id":"pentair_25021-0223s","title":"Pentair Small Cartridge for System 3 Filters | 25021-0223S","description":"\u003cp\u003eThe Pentair Small Cartridge (25021-0223S) is the OEM replacement 136 sq. ft. inner filter module for the System 3 Modular Media Filter, model S7M400.\u003c\/p\u003e\n\u003ch3\u003eWhat It Does\u003c\/h3\u003e\n\u003cp\u003eThis module is the inner replacement element of the System 3's two-piece modular media design. It provides the filtration surface area that captures debris as pool water passes through the filter tank, and is designed to be replaced as a standalone module without requiring tank disassembly or replacement.\u003c\/p\u003e\n\u003cp\u003eThis is the smaller, inner cartridge for the S7M400.  For the matching larger, outer cartridge, see part number \u003ca href=\"https:\/\/poolaroo.com\/products\/pentair_25022-0224s\"\u003e\u003cstrong\u003e25022-0224S\u003c\/strong\u003e\u003c\/a\u003e.  Replace both to complete your filter service.\u003c\/p\u003e\n\u003cp\u003eFor a combo back of both filter cartridges, see the combo pack: \u003ca href=\"https:\/\/poolaroo.com\/products\/pentair_170146\"\u003e\u003cstrong\u003e170146\u003c\/strong\u003e\u003c\/a\u003e\u003c\/p\u003e\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; margin: 20px 0; border: 1px solid #ccc;\"\u003e\n\u003ctbody\u003e\n\u003ctr style=\"background-color: #f8f9fa;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003ePentair Part Number\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e25021-0223S\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #ffffff;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003ePart Name\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003eSmall Cartridge\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #f8f9fa;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eQuantity Included\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003eEach\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #ffffff;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eCompatible Model\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003eS7M400\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eFits Into\u003c\/h3\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; margin: 20px 0; border: 1px solid #ccc;\"\u003e\n\u003ctbody\u003e\n\u003ctr style=\"background-color: #f8f9fa;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eBrand\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eEquipment Line\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eModel \/ Part Number\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e\u003cstrong\u003eNotes\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #ffffff;\"\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003ePentair\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003eSystem 3\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003eS7M400\u003c\/td\u003e\n\u003ctd style=\"border: 1px solid #ccc; padding: 10px;\"\u003e136 sq. ft. Inner Replacement Module\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e\u003cem\u003eCompatibility is based on Pentair parts documentation and available OEM records. This is not an exhaustive list. For certainty, verify the part number in your equipment's manual or on the original part itself before ordering.\u003c\/em\u003e\u003c\/p\u003e\n\u003ch3\u003ePoolaroo Pro Tip\u003c\/h3\u003e\n\u003cp\u003eThe shallow-pleat design of this module allows for quick maintenance — a garden hose rinse is typically enough to clear routine debris between deep cleanings. Inspect the module each season for torn media, cracked end caps, or a collapsed core, and replace it if damage is found to keep filtration area and system flow rate at spec.\u003c\/p\u003e\n\u003c!-- wft:processed:manual:2026-08-24 --\u003e","brand":"Pentair","offers":[{"title":"Default Title","offer_id":54309090525459,"sku":"25021-0223S","price":289.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0920\/0687\/5411\/files\/PEN250210223S_0.jpg?v=1781714193","url":"https:\/\/poolaroo.com\/products\/pentair_25021-0223s","provider":"Poolaroo","version":"1.0","type":"link"}