{"product_id":"2-5-x-21-freshwater-reverse-osmosis-membrane","title":"2.5\" x 21\" Freshwater Reverse Osmosis Membrane","description":"\u003cp\u003e\u003cstrong\u003eIs your whole house RO making less water than it used to, or is the TDS reading on the purified side creeping up?\u003c\/strong\u003e In 400 to 1,000 GPD Crystal Quest systems, the 2.5\" x 21\" elements do the purifying, so their condition decides how much water you get and how clean it tastes.\u003c\/p\u003e\u003cp\u003eThe Crystal Quest 2.5\" x 21\" Freshwater Reverse Osmosis Membrane (CQE-RC-04084, the 2521 element size) is a low-energy, thin-film composite (TFC) element for pre-filtered, dechlorinated municipal or well water. It is the replacement element listed for the 400, 500 and 1,000 GPD \u003ca href=\"https:\/\/crystalquest.com\/products\/whole-house-reverse-osmosis-system\"\u003eWhole House Reverse Osmosis System\u003c\/a\u003e and the same sizes of the Commercial and Medical Mid-Flow RO Systems.\u003c\/p\u003e\u003ch3\u003eAt a glance\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCounts by system:\u003c\/strong\u003e one for 400 GPD, two for 500 GPD and three for 1,000 GPD on the Whole House RO\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLow-energy freshwater class:\u003c\/strong\u003e for tap and well water under 2,000 ppm TDS, rated at 150 psi operating pressure\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSystem performance:\u003c\/strong\u003e Crystal Quest whole house RO systems are rated for 98.5% nominal and 96% minimum salt rejection\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLong service life:\u003c\/strong\u003e plan on 2 to 3 years; actual life depends on feed water quality, system configuration and usage\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eWhat you are looking at\u003c\/h3\u003e\u003cp\u003eA 21\" spiral-wound element. Leaves of TFC membrane, separated by a mesh feed spacer, wrap around a perforated permeate tube. Feed water travels along the spacer channels; purified water (permeate) passes through the membrane and spirals into the center tube, while the concentrate leaves the far end carrying the rejected minerals. A brine seal on the inlet end seals the element to the housing wall so every gallon passes through it, not around it. It ships in preservative solution with protectors on each end of the permeate tube. The 21\" length fits only housings built for it; it is not interchangeable with 2.5\" x 14\" or 2.5\" x 40\" elements.\u003c\/p\u003e\u003ch3\u003eHow it purifies water\u003c\/h3\u003e\u003ch4\u003ePressure against osmosis\u003c\/h4\u003e\u003cp\u003eDissolved salts create osmotic pressure that pulls water toward the saltier side of a membrane. The system pump pushes harder than that pull, driving water molecules through the membrane while dissolved ions stay in the feed stream. Crystal Quest rates its whole house RO elements at 150 psi operating pressure.\u003c\/p\u003e\u003ch4\u003eWhy there is a drain line\u003c\/h4\u003e\u003cp\u003eThe concentrate stream sweeps the membrane surface as it flows, which is how an element runs for years instead of clogging like a cartridge. A Crystal Quest RO system sends about 1 gallon to drain for every 1 to 3 gallons of purified water, set to your water chemistry.\u003c\/p\u003e\u003ch4\u003eWhy winter output drops\u003c\/h4\u003e\u003cp\u003eColder water passes through the membrane more slowly, and higher TDS raises the osmotic pressure the pump has to beat. Production returns as the water warms; if it does not, check the pre-filters, then rejection and flow.\u003c\/p\u003e\u003ch3\u003eWhat it reduces\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003ePrimary target:\u003c\/strong\u003e total dissolved solids (TDS): the hardness minerals, sodium, chloride and sulfate behind scale, spotting and salty or mineral taste. Crystal Quest whole house RO systems are rated for 96% minimum and 98.5% nominal salt rejection.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eAlso held back:\u003c\/strong\u003e any particle that reaches the membrane, microplastics included, is far too large to pass. The pre-filters remove most of them first.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eNot designed to handle:\u003c\/strong\u003e free chlorine (0.1 ppm maximum, so remove it upstream), sediment, and iron or manganese above 0.05 ppm. Feed hardness should be under 15 gpg on the 400 GPD system and under 5 gpg on 500 and 1,000 GPD systems; harder water scales the membrane, so soften first. Brackish groundwater and seawater need a brackish or seawater desal element instead.\u003c\/p\u003e\u003ch3\u003eWhy Crystal Quest\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eThe listed element and count\u003c\/strong\u003e for your Crystal Quest system, straight from our replacement tables.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete specs:\u003c\/strong\u003e operating limits and feed water limits in the Specifications tab.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOver 1,000,000 people served since 1994.\u003c\/strong\u003e Crystal Quest builds under ISO 9001 quality management, has made water filtration in the USA for over 30 years and offers lifetime support by phone, email or chat.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eWhere it fits\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e\u003ca href=\"https:\/\/crystalquest.com\/products\/whole-house-reverse-osmosis-system\"\u003eWhole House Reverse Osmosis System\u003c\/a\u003e:\u003c\/strong\u003e 400 GPD (1), 500 GPD (2), 1,000 GPD (3).\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e\u003ca href=\"https:\/\/crystalquest.com\/products\/reverse-osmosis-system-mid-flow\"\u003eCommercial Mid-Flow\u003c\/a\u003e and \u003ca href=\"https:\/\/crystalquest.com\/products\/medical-mid-flow-reverse-osmosis-system-500-7000-gpd\"\u003eMedical Mid-Flow\u003c\/a\u003e RO Systems,\u003c\/strong\u003e 500 and 1,000 GPD: use the quantity in your system's replacement table.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNot this element:\u003c\/strong\u003e the 300 GPD Whole House RO and 200 GPD Low-Flow RO use the \u003ca href=\"https:\/\/crystalquest.com\/products\/2-5-x-14-ro-membrane\"\u003e2.5\" x 14\" element\u003c\/a\u003e; 750 to 2,500 GPD systems use the \u003ca href=\"https:\/\/crystalquest.com\/products\/2-5-x-40-ro-membrane\"\u003e2.5\" x 40\" element\u003c\/a\u003e.\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eRO membranes are not returnable under our \u003ca href=\"https:\/\/crystalquest.com\/policies\/refund-policy\"\u003erefund policy\u003c\/a\u003e. Confirm the part number on your current element, or call us and we will confirm it with you.\u003c\/p\u003e\u003ch3\u003eStandard 2521 format\u003c\/h3\u003e\u003cp\u003eThis is a low-energy freshwater element in the standard 2521 (2.5\" x 21\") format used in 2.5\" membrane housings built for 21\" elements, including Crystal Quest systems. Crystal Quest rates its whole house RO elements at 150 psi operating pressure, well below what brackish water and seawater elements are built for, so the pump does less work on tap and well water. A shared format name is a good start, not a guarantee: if your system is not a Crystal Quest model, compare the brine seal position, permeate tube ends and flow direction with your current element, or \u003ca href=\"https:\/\/crystalquest.com\/pages\/contact-us\"\u003econtact us\u003c\/a\u003e before ordering.\u003c\/p\u003e\u003ch3\u003eStorage and handling\u003c\/h3\u003e\u003cp\u003eEach element ships sealed in its bag in a preservative solution. Keep it sealed until you are ready to install it, store it indoors out of direct sunlight, and never let it freeze. Once an element has been installed and wetted, do not let it dry out. If your system will sit idle for a season, \u003ca href=\"https:\/\/crystalquest.com\/products\/membrane-persavtive\"\u003eMembrane Preservative\u003c\/a\u003e is used to protect the elements against damage from bacterial growth.\u003c\/p\u003e\u003ch3\u003eCommon questions\u003c\/h3\u003e\u003cdiv class=\"cq-product-faq\"\u003e\n\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eWhich systems use the 2.5\" x 21\" element?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eThe 400, 500 and 1,000 GPD Whole House Reverse Osmosis System, and the 500 and 1,000 GPD Commercial and Medical Mid-Flow RO Systems.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eHow many elements do I need?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eUse the count in your system's replacement table. On the Whole House Reverse Osmosis System it is one for 400 GPD, two for 500 GPD and three for 1,000 GPD.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eShould I replace all the elements at once?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eYes. On two- and three-element systems, replacing the full set keeps the elements sharing the load evenly and resets your performance baseline.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eHow long does a 2521 RO membrane last?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003ePlan on 2 to 3 years. Actual life depends on feed water quality, system configuration and usage. Good pre-filtration, softening where needed and routine flushing help it reach the full span.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eDo I need to flush a new element?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eYes. New elements ship in a preservative solution. Flush for at least 1 hour and discard all permeate and concentrate made during the flush.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eCan chlorinated city water go straight to the membrane?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eNo. The thin-film membrane tolerates no more than 0.1 ppm free chlorine, so the carbon and SMART pre-filters must remove chlorine first. Change them on schedule to protect the element.\u003c\/p\u003e\u003c\/details\u003e\u003cdetails\u003e\u003csummary\u003e\u003cstrong\u003eFreshwater, brackish or seawater?\u003c\/strong\u003e\u003c\/summary\u003e\u003cp\u003eThis is the freshwater element, for feed water under 2,000 ppm TDS. Choose the class your system and feed water are designed for, and ask Crystal Quest if you are unsure.\u003c\/p\u003e\u003c\/details\u003e\n\u003c\/div\u003e\n###\n\u003ch3\u003eElement specifications\u003c\/h3\u003e\u003ctable width=\"100%\"\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003e\u003cstrong\u003eValue\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eMembrane type\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003eThin-film composite (TFC) reverse osmosis element\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eApplication\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003eFreshwater (low energy)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eElement size\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003e2.5\" x 21\" (2521 format)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003ePart number\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003eCQE-RC-04084\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eListed replacement for\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003eWhole House Reverse Osmosis System 400 GPD (1), 500 GPD (2), 1,000 GPD (3); Commercial and Medical Mid-Flow RO Systems 500 and 1,000 GPD (quantity per system table)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eFeed water\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003ePre-filtered and dechlorinated; free chlorine 0.1 ppm maximum\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eStart-up\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003eFlush at least 1 hour; discard all permeate and concentrate from the flush\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd valign=\"middle\"\u003eService life\u003c\/td\u003e\n\u003ctd valign=\"middle\"\u003e2 to 3 years*\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\u003cp\u003e\u003cstrong\u003eElement operating limits\u003c\/strong\u003e\u003c\/p\u003e\u003ctable width=\"100%\"\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eRated production\u003c\/td\u003e\n\u003ctd\u003e400 GPD at 150 psi, 550 ppm feed, 77°F (25°C), 15% recovery; actual output drops with colder or saltier water\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNominal salt rejection\u003c\/td\u003e\n\u003ctd\u003e99% (96% minimum) at 550 ppm feed, 150 psi, 77°F (25°C), 15% recovery\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating pressure\u003c\/td\u003e\n\u003ctd\u003eRated maximum: 600 psi; suggested operating range: 100 to 150 psi\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum temperature\u003c\/td\u003e\n\u003ctd\u003e113°F (45°C)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003epH range\u003c\/td\u003e\n\u003ctd\u003eRated 2 to 11; suggested 5 to 11 for continuous operation; cleaning 2 to 12\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFree chlorine tolerance\u003c\/td\u003e\n\u003ctd\u003e0.1 ppm maximum. Remove chlorine and chloramine before the membrane with carbon pre-filtration (Crystal Quest whole house RO systems include this).\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum turbidity\u003c\/td\u003e\n\u003ctd\u003e1 NTU\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSilt density index\u003c\/td\u003e\n\u003ctd\u003eLess than 5 SDI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\u003cp\u003e\u003cstrong\u003eFeed water limits for the system\u003c\/strong\u003e\u003c\/p\u003e\u003ctable width=\"100%\"\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eTotal dissolved solids\u003c\/td\u003e\n\u003ctd\u003eUnder 2,000 ppm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHardness\u003c\/td\u003e\n\u003ctd\u003eUnder 15 gpg (400 GPD); under 5 gpg (500 and 1,000 GPD)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIron and manganese\u003c\/td\u003e\n\u003ctd\u003eUnder 0.05 ppm each\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSilica and organics\u003c\/td\u003e\n\u003ctd\u003eUnder 1 ppm each\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFree chlorine\u003c\/td\u003e\n\u003ctd\u003eNone (remove upstream)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFeed temperature\u003c\/td\u003e\n\u003ctd\u003e40°F to 105°F\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\u003cp\u003e*Service life is an estimate. Actual life depends on feed water quality, system configuration and usage. System figures are from the Crystal Quest whole house RO manuals; production falls with colder or higher-TDS water. Element ratings are from the element data sheet. The 600 psi rating is the element's structural limit. Low energy elements are designed to make their rated flow at about 150 psi.\u003c\/p\u003e\u003cp\u003e\u003cimg width=\"1024\" height=\"571\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/1286\/9985\/files\/RO_Membrane_Illustration_1024x1024.png?v=1615830985\" alt=\"Illustration of a Crystal Quest low energy freshwater reverse osmosis membrane element\"\u003e\u003c\/p\u003e","brand":"Crystal Quest Water Filters","offers":[{"title":"Single","offer_id":67868658630889,"sku":"CQE-RC-04084","price":162.25,"currency_code":"USD","in_stock":true},{"title":"Pack of 2","offer_id":67868658663657,"sku":"CQE-RC-04084-2PK","price":324.5,"currency_code":"USD","in_stock":true},{"title":"Pack of 4","offer_id":67868658696425,"sku":"CQE-RC-04084-4PK","price":649.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0814\/4512\/6377\/files\/2-5-x-21-tfc-single-reverse-osmosis-membranes-crystal-quest-water-filter-cartridges-1263586039_56f087eb-7188-41b8-a85d-7884c3d4f6c9.webp?v=1793834585","url":"https:\/\/clearwaterworld.com\/products\/2-5-x-21-freshwater-reverse-osmosis-membrane","provider":"Clearwater World","version":"1.0","type":"link"}