{"product_id":"flamco-flexvent-automatic-air-vent-with-shut-off-valve-27740-bsp-and-27750-bsp","title":"Flamco Flexvent Automatic Air Vent with Shut-Off Valve – 27740 (½\" BSP) and 27750 (⅜\" BSP)","description":"\u003c!-- SEO Product Name: Flamco Flexvent Automatic Air Vent with Shut-Off Valve – MPN 27740 (½\" BSP) and 27750 (⅜\" BSP) --\u003e\n\n\u003cdiv style=\"font-family: Arial, sans-serif; color: #1a1a1a; max-width: 900px; line-height: 1.7;\"\u003e\n\n  \u003c!-- Intro --\u003e\n  \u003cp style=\"font-size: 15px;\"\u003eThe \u003cstrong\u003eFlamco Flexvent\u003c\/strong\u003e is a compact, float-operated automatic air vent for sealed heating and cooling systems. A proven design with decades of market use, it continuously vents trapped air from the highest points of a system without manual intervention — preventing corrosion, noisy pipework, cold spots in radiators, and reduced heat transfer efficiency. The brass body contains an all-plastic interior mechanism: when air collects in the housing the float drops, opening the vent valve to release the air; once the air is expelled the rising water level lifts the float closed again.\u003c\/p\u003e\n\n  \u003cp style=\"font-size: 15px;\"\u003eBoth variants include an integrated \u003cstrong\u003eshut-off valve\u003c\/strong\u003e, allowing the vent to be isolated and removed for maintenance without draining the system. The ½\" and ⅜\" versions share the same 30mm diameter body — connection size is the only difference. A \u003cstrong\u003ecaptive cap\u003c\/strong\u003e with open\/close function prevents leaks when the vent is closed, and the self-sealing notched gasket on the valve sleeve means \u003cstrong\u003eno PTFE tape or thread sealant is required\u003c\/strong\u003e during installation. All Flexvents are individually tested at the factory before dispatch. Compatible with glycol-based antifreeze at concentrations up to 50%.\u003c\/p\u003e\n\n  \u003c!-- Badge strip --\u003e\n  \u003cdiv style=\"display: flex; flex-wrap: wrap; gap: 8px; margin: 22px 0;\"\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003e27740 — ½\" BSP\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003e27750 — ⅜\" BSP\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eIntegrated Shut-Off Valve\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eNo Tape Required\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eFactory Tested\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eGlycol Compatible (50%)\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eHeating \u0026amp; Cooling\u003c\/span\u003e\n    \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eBrass Housing\u003c\/span\u003e\n  \u003c\/div\u003e\n\n  \u003c!-- Variant table --\u003e\n  \u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eVariant Specifications\u003c\/h2\u003e\n\n  \u003ctable style=\"width: 100%; border-collapse: collapse; font-size: 14px; margin-bottom: 8px;\"\u003e\n    \u003cthead\u003e\n      \u003ctr style=\"background: #008377CF; color: #fff;\"\u003e\n        \u003cth style=\"padding: 10px 12px; text-align: left; border: 1px solid #006b62;\"\u003eParameter\u003c\/th\u003e\n        \u003cth style=\"padding: 10px 12px; text-align: left; border: 1px solid #006b62;\"\u003e27740 — Flexvent ½\"\u003c\/th\u003e\n        \u003cth style=\"padding: 10px 12px; text-align: left; border: 1px solid #006b62;\"\u003e27750 — Flexvent ⅜\"\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMPN\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold; color: #008377;\"\u003e27740\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold; color: #008377;\"\u003e27750\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eGTIN\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e—\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e08712874277502\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eConnection\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eR½\" male — BSPT (ISO 7-1)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eR⅜\" male — BSPT (ISO 7-1)\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eOuter pipe diameter\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e21.3mm\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e17.2mm\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eBody diameter (Ø)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e30mm\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e30mm\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eHeight (H)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e75.5mm\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e78mm\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eWeight\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eapprox. 0.11 kg\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e0.108 kg\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003ePackaging (H × W × L)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e—\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e112 × 39 × 39mm\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eShut-off valve\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eYes\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eYes\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMin working temperature\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e-10°C\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e-10°C\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMax working temperature (continuous)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e90°C\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e90°C\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMax temperature (peak load)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e120°C\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e120°C\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMin working pressure\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e0.2 Bar\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e0.2 Bar\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMax working pressure\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e6.0 Bar\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e6.0 Bar\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMax pressure (peak load)\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e10.0 Bar\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e10.0 Bar\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eGlycol compatibility\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eUp to 50% concentration\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eUp to 50% concentration\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eHousing material\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eBrass\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eBrass\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eInternal mechanism\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eAll plastic float mechanism\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eAll plastic float mechanism\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr style=\"background: #f0faf9;\"\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eSuitable for\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eHeating, cooling, closed systems\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eHeating, cooling, closed systems\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eManufacturer\u003c\/td\u003e\n        \u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\" colspan=\"2\"\u003eFlamco BV (Aalberts NV), Netherlands\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003cp style=\"font-size: 12px; color: #555; margin-bottom: 24px;\"\u003eThe ½\" (27740) is the standard choice for most heating system tappings and boiler flow headers. The ⅜\" (27750) is used where the tapping or fitting calls for a smaller connection — common on older radiator valve bodies, some boiler air vent bosses, and branch tees with ⅜\" female sockets. Both share the same body diameter and mechanism.\u003c\/p\u003e\n\n  \u003c!-- Key features grid --\u003e\n  \u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eKey Features\u003c\/h2\u003e\n\n  \u003cdiv style=\"display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 14px; margin-bottom: 24px;\"\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eFloat-operated — fully automatic\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eThe all-plastic float mechanism operates entirely by the water level in the housing. No servicing, adjusting, or manual operation is required during normal system running. The \u003cstrong\u003esubstantial distance between water and the closing mechanism\u003c\/strong\u003e reduces contamination risk, and the large air cushion at the top of the housing prevents the valve seat from being wetted by system debris.\u003c\/p\u003e\n    \u003c\/div\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eIntegrated shut-off valve\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eThe built-in valve sleeve allows the vent to be isolated from system pressure without draining — the vent can be removed, inspected, or replaced during maintenance while the system stays pressurised. The valve sleeve threads include a \u003cstrong\u003eself-sealing notched gasket\u003c\/strong\u003e — no PTFE tape or jointing compound is needed on installation.\u003c\/p\u003e\n    \u003c\/div\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eCaptive cap — leak prevention\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eThe captive (retained) top cap cannot be removed or lost — it stays attached to the body. In the closed position it seals the vent port with integral expansion sealing rings, preventing drips during system pressurisation and when the vent is screwed fully closed. In the open position the cap allows free air discharge.\u003c\/p\u003e\n    \u003c\/div\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eGlycol compatible — heat pump \u0026amp; solar ready\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eCompatible with glycol-based antifreeze at concentrations up to 50% — making the Flexvent suitable for \u003cstrong\u003eair source heat pump external circuits, ground source brine circuits, solar thermal primary circuits\u003c\/strong\u003e, and any other closed system where glycol is used for freeze protection. Rated to -10°C working temperature with peak load tolerance to 120°C.\u003c\/p\u003e\n    \u003c\/div\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eCompact — 30mm body, fits anywhere\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eBoth variants share a 30mm body diameter and under 80mm height — small enough to fit in boiler cabinets, on pipework headers, at the top of micro-bore manifolds, and in any tight space where air typically collects. Flamco has designed the Flexvent range to be easy to install in any orientation of the connected pipework.\u003c\/p\u003e\n    \u003c\/div\u003e\n    \u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 14px 16px;\"\u003e\n      \u003cp style=\"margin: 0 0 5px; font-weight: bold; color: #008377CF; font-size: 14px;\"\u003eFactory tested — individually\u003c\/p\u003e\n      \u003cp style=\"margin: 0; font-size: 13px;\"\u003eEvery Flexvent is tested at the Flamco factory before leaving — not batch tested or sample tested. This gives confidence that each unit will perform correctly on installation. Flamco has manufactured automatic air vents since 1956 and the Flexvent is one of the most widely specified and trusted designs in the European heating industry.\u003c\/p\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\n  \u003c!-- Installation note --\u003e\n  \u003cdiv style=\"background: #fff8e1; border-left: 4px solid #f59e0b; padding: 12px 16px; margin: 0 0 24px; font-size: 14px; border-radius: 0 4px 4px 0;\"\u003e\n    \u003cstrong style=\"color: #b45309;\"\u003eInstallation requirements:\u003c\/strong\u003e Install the Flexvent \u003cstrong\u003evertically, with the connection at the bottom\u003c\/strong\u003e and the vent cap uppermost — the float mechanism depends on gravity and will not function correctly in any other orientation. Install at the highest points of the system where air naturally collects. Leave accessible for maintenance — do not bury in insulation. Install in a frost-free location. Ensure the captive cap is in the \u003cstrong\u003eopen position\u003c\/strong\u003e after installation to allow air venting during system filling and commissioning.\n  \u003c\/div\u003e\n\n  \u003c!-- Related products footer --\u003e\n  \u003cdiv style=\"background: #008377CF; color: #fff; padding: 16px 20px; border-radius: 4px; margin-top: 32px; font-size: 14px; line-height: 1.9;\"\u003e\n    \u003cstrong\u003eRelated Products:\u003c\/strong\u003e\u003cbr\u003e\n    Flamco Flexvent 27740 ½\" (single) | Flamco Flexvent 27750 ⅜\" (single) | Flamco Flexvent Box of 50 (27740) | Intatec IntaKlean HP Magnetic Filter | Sentinel X100 System Inhibitor | Flamco Fill \u0026amp; Drain Valve | Boiler Tapping ½\" Female Boss\n  \u003c\/div\u003e\n\n\u003c\/div\u003e","brand":"Flamco","offers":[{"title":"½\" BSP","offer_id":63900260827485,"sku":"27740","price":19.0,"currency_code":"GBP","in_stock":true},{"title":"⅜\" BSP","offer_id":63900260860253,"sku":"27750","price":17.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0958\/2051\/3629\/files\/FlamcoFlexventAutomaticAirVent.webp?v=1773815714","url":"https:\/\/qualityheating.co.uk\/products\/flamco-flexvent-automatic-air-vent-with-shut-off-valve-27740-bsp-and-27750-bsp","provider":"AIZO Quality Heating","version":"1.0","type":"link"}