{"product_id":"shurflo-181-201-fresh-water-accumulator-tank-21-oz","title":"Shurflo 181-201 Fresh Water Accumulator Tank, 21 oz","description":"\u003cp class=\"nvn-hero\"\u003eThe Shurflo by Pentair 181-201 fresh water accumulator tank stops your 12 volt pump from short-cycling every time you crack a faucet. A 21-ounce butyl bladder stores a cushion of pressurized water, so small draws feed off the tank instead of kicking the pump on. Compact, NSF-listed, and rated to 125 PSI for boat and RV fresh water systems.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eThe Shurflo by Pentair 181-201 is a fresh water accumulator tank, and it does one job really well. It smooths out the pressure in your boat or RV plumbing so the pump stops hammering on and off every time someone cracks a faucet. If you've ever heard your water pump chatter through a quick hand rinse, or felt the water surge and sputter at the galley tap, this is the part that fixes it.\u003c\/p\u003e\n\u003cp\u003eHere's how it works. The tank holds 21 ounces of water behind a butyl bladder, with a pre-charged air cushion on the other side. When the pump builds pressure, it packs a little extra water into the tank against that air charge. Then, when you open a tap for a short draw, that stored water feeds the line first. The pump doesn't even wake up for small demands. For longer draws it still runs, but it cycles far less, and that's easier on the motor, the check valve, and your ears.\u003c\/p\u003e\n\u003cp\u003eWe see these go into two kinds of systems all the time. On boats, it mounts down near the fresh water pump, often behind a headliner or tucked into a locker on a 28 to 32 foot sailboat. Give yourself about 3 inches of clearance at the port end so you can get a wrench on the fittings later. On RVs and campers it lives in the water bay or under the galley sink. Either way the footprint is compact, 8-3\/4 inches long and 3-3\/4 inches around, so it fits where a bigger tank won't.\u003c\/p\u003e\n\u003cp\u003ePlumbing it in is straightforward. Both ends are 1\/2 inch-14NPSM male ports, so it drops inline on standard 1\/2 inch fittings, pump side in, fixture side out. Use PTFE tape on the threads and snug them by hand plus a light turn with a wrench. Don't crank on them. The body is nylon, and if you overtighten a fitting into a nylon port you can crack it. On a boat, a little dielectric grease on stainless fittings keeps the threads from seizing down the road.\u003c\/p\u003e\n\u003cp\u003ePre-charge matters. Set the air side a couple psi below your pump's cut-in pressure, which for most 12 volt diaphragm pumps lands around 20 psi. That's the sweet spot where the tank absorbs the small draws before the pump ever starts. Pair it with a fixed-speed diaphragm pump like the Shurflo 2088 and you'll really notice the difference in short-cycling. Running a variable-speed pump that already ramps smoothly? You'll see less benefit, since that pump is doing some of the same work electronically.\u003c\/p\u003e\n\u003cp\u003eThe bladder is butyl and the body is rated to 125 PSI, well above any normal fresh water system pressure, so it's got plenty of headroom. It's CSA and NSF listed, which means it's approved for potable water. The bladder keeps the air charge separated from the water you drink, so nothing tastes like a bike tire. Mounting is two 7\/32 inch D-holes spaced 4-1\/16 inches on center. Bolt it flat to a bulkhead. On a planing hull or an aluminum boat where engine vibration is real, use locknuts or a dab of thread locker so the mounts don't shake loose over a season.\u003c\/p\u003e\n\u003cp\u003eWhat it's not: a substitute for a properly sized pump or a fresh water tank. The 21 ounce reserve is a buffer, not a supply. If you've got two faucets wide open on a liveaboard, the pump will still run steadily, and that's normal. This tank is about killing the annoying rapid cycling on the small, frequent draws that make up most of a day aboard. For that, it earns its spot. Set the pre-charge right, don't overtighten the ports, and it'll quietly do its job for years.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003e21-ounce reserve capacity holds a cushion of pressurized water so short draws feed off the tank instead of starting the pump\u003c\/li\u003e\n  \u003cli\u003eButyl bladder rated to 125 PSI keeps the air charge separated from potable water and holds pressure without waterlogging\u003c\/li\u003e\n  \u003cli\u003eNylon body in matte black shrugs off the damp of a bilge or RV water bay\u003c\/li\u003e\n  \u003cli\u003e1\/2 inch-14NPSM male ports on both ends plumb inline on standard 1\/2 inch fittings\u003c\/li\u003e\n  \u003cli\u003eTwo 7\/32 inch D-holes on 4-1\/16 inch centers bolt flat to a bulkhead or panel\u003c\/li\u003e\n  \u003cli\u003eCSA and NSF listed for potable fresh water systems\u003c\/li\u003e\n  \u003cli\u003eCompact 8-3\/4 x 3-3\/4 inch footprint tucks behind a headliner or under a galley sink\u003c\/li\u003e\n  \u003cli\u003ePre-chargeable air side lets you tune the cut-in cushion to your pump\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cdiv class=\"nvn-trust\"\u003e\n  \u003ch2\u003eWhy Buy from NVN Marine\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eAuthorized Shurflo by Pentair reseller, full manufacturer warranty\u003c\/li\u003e\n    \u003cli\u003eNMEA member and ABYC certified, advice from real boat techs\u003c\/li\u003e\n    \u003cli\u003eSame-day shipping before 3 PM ET on in-stock items\u003c\/li\u003e\n    \u003cli\u003eNY headquarters and Fort Lauderdale flagship retail store\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"nvn-faq\"\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat does the Shurflo 181-201 accumulator tank actually do?\u003c\/summary\u003e\n    \u003cp\u003eIt stores a small cushion of pressurized water so your pump doesn't cycle on and off for every short draw. Open a tap briefly and the stored water feeds the line first, which cuts pump short-cycling and steadies the flow at the fixture.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhere does it install in the water system?\u003c\/summary\u003e\n    \u003cp\u003eInline on the pressure side, right after the fresh water pump and before your fixtures. Both ports are 1\/2 inch-14NPSM male, so it plumbs in on standard 1\/2 inch fittings, pump side in and fixture side out.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat pre-charge pressure should I set?\u003c\/summary\u003e\n    \u003cp\u003eSet the air side a couple psi below your pump's cut-in pressure. For most 12 volt diaphragm pumps that's around 20 psi. Too high and the tank never fills, too low and it won't hold a useful cushion.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill it work with my water pump?\u003c\/summary\u003e\n    \u003cp\u003eIt works best with fixed-speed diaphragm pumps, where it noticeably cuts short-cycling. If you run a variable-speed pump that already ramps smoothly, you'll see less benefit since the pump handles some of that electronically.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs it safe for drinking water?\u003c\/summary\u003e\n    \u003cp\u003eYes. It's CSA and NSF listed for potable water, and the butyl bladder keeps the air charge separated from the water, so there's no rubbery taste.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat size are the ports?\u003c\/summary\u003e\n    \u003cp\u003eBoth ends use 1\/2 inch-14NPSM male threads. Use PTFE tape and hand-tighten plus a light wrench turn. The body is nylon, so don't overtighten or you can crack the port.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow do I mount it?\u003c\/summary\u003e\n    \u003cp\u003eIt has two 7\/32 inch D-holes spaced 4-1\/16 inches on center. Bolt it flat to a bulkhead or panel. On boats with real engine vibration, use locknuts so the mounts don't work loose.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow much water does it hold?\u003c\/summary\u003e\n    \u003cp\u003e21 ounces. That's a buffer for small, frequent draws, not a water supply. With two faucets wide open the pump will still run steadily, and that's normal.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat's the maximum pressure rating?\u003c\/summary\u003e\n    \u003cp\u003eThe tank is rated up to 125 PSI, well above any normal fresh water system pressure, so there's plenty of headroom for a typical 12 volt setup.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow big is it?\u003c\/summary\u003e\n    \u003cp\u003eIt's 8-3\/4 inches long and 3-3\/4 inches in diameter, compact enough to tuck behind a headliner, in an RV water bay, or under a galley sink.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable class=\"nvn-specs\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eTitle\u003c\/th\u003e\n\u003ctd\u003eShurflo by Pentair 181-201 Fresh Water Accumulator Tank\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eShurflo by Pentair\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer Part Number\u003c\/th\u003e\n\u003ctd\u003e181-201\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e752324309801\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCapacity\u003c\/th\u003e\n\u003ctd\u003e21 Ounce\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eLength\u003c\/th\u003e\n\u003ctd\u003e8-3\/4 Inch\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eDiameter\u003c\/th\u003e\n\u003ctd\u003e3-3\/4 Inch\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003ePort Threads\u003c\/th\u003e\n\u003ctd\u003e1\/2 Inch-14NPSM Male\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMaximum Pressure\u003c\/th\u003e\n\u003ctd\u003eUp To 125 PSI\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eColor\u003c\/th\u003e\n\u003ctd\u003eBlack\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eFinish\u003c\/th\u003e\n\u003ctd\u003eMatte\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBody Material\u003c\/th\u003e\n\u003ctd\u003eNylon\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBladder Material\u003c\/th\u003e\n\u003ctd\u003eButyl\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMounting Holes\u003c\/th\u003e\n\u003ctd\u003eTwo 7\/32 Inch D Holes\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eMounting Centerline\u003c\/th\u003e\n\u003ctd\u003e4-1\/16 Inch Apart\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCertifications\u003c\/th\u003e\n\u003ctd\u003eCSA \/ NSF Listed\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@type\": \"FAQPage\",\n    \"mainEntity\": [\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What does the Shurflo 181-201 accumulator tank actually do?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It stores a small cushion of pressurized water so your pump doesn't cycle on and off for every short draw. Open a tap briefly and the stored water feeds the line first, which cuts pump short-cycling and steadies the flow at the fixture.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Where does it install in the water system?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Inline on the pressure side, right after the fresh water pump and before your fixtures. Both ports are 1\/2 inch-14NPSM male, so it plumbs in on standard 1\/2 inch fittings, pump side in and fixture side out.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What pre-charge pressure should I set?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Set the air side a couple psi below your pump's cut-in pressure. For most 12 volt diaphragm pumps that's around 20 psi. Too high and the tank never fills, too low and it won't hold a useful cushion.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will it work with my water pump?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It works best with fixed-speed diaphragm pumps, where it noticeably cuts short-cycling. If you run a variable-speed pump that already ramps smoothly, you'll see less benefit since the pump handles some of that electronically.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is it safe for drinking water?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Yes. It's CSA and NSF listed for potable water, and the butyl bladder keeps the air charge separated from the water, so there's no rubbery taste.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What size are the ports?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Both ends use 1\/2 inch-14NPSM male threads. Use PTFE tape and hand-tighten plus a light wrench turn. The body is nylon, so don't overtighten or you can crack the port.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How do I mount it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It has two 7\/32 inch D-holes spaced 4-1\/16 inches on center. Bolt it flat to a bulkhead or panel. On boats with real engine vibration, use locknuts so the mounts don't work loose.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How much water does it hold?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"21 ounces. That's a buffer for small, frequent draws, not a water supply. With two faucets wide open the pump will still run steadily, and that's normal.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What's the maximum pressure rating?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"The tank is rated up to 125 PSI, well above any normal fresh water system pressure, so there's plenty of headroom for a typical 12 volt setup.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How big is it?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's 8-3\/4 inches long and 3-3\/4 inches in diameter, compact enough to tuck behind a headliner, in an RV water bay, or under a galley sink.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Shurflo by Pentair","offers":[{"title":"Default Title","offer_id":45069142720605,"sku":"2009041","price":55.49,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_11bbad0c-a3ca-4d59-bca3-bf0762d51bff.jpg?v=1789690911","url":"https:\/\/nvnmarine.com\/products\/shurflo-181-201-fresh-water-accumulator-tank-21-oz","provider":"NVN Marine","version":"1.0","type":"link"}