{"product_id":"caleffi-series-5080-hygroscopic-automatic-radiator-air-vent-508041-half-inch-bsp","title":"Caleffi Series 5080 Hygroscopic Automatic Radiator Air Vent 508041 Half Inch BSP","description":"\u003cdiv style=\"font-size:16px; max-width:900px; font-family:Arial,Helvetica,sans-serif; color:#222; line-height:1.6;\"\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eCaleffi Series 5080 Hygroscopic Automatic Radiator Air Vent (MPN 508041)\u003c\/strong\u003e is a \u003cstrong\u003e½\" BSP male-threaded automatic air bleeding valve\u003c\/strong\u003e for panel and column radiators. It operates on Caleffi's \u003cstrong\u003ehygroscopic cellulose disc principle\u003c\/strong\u003e: when system water is present, the cellulose discs \u003cstrong\u003eexpand by 50%, sealing the vent outlet\u003c\/strong\u003e; when air accumulates, the discs dry out and contract, releasing trapped air automatically. The \u003cstrong\u003enickel-plated brass body\u003c\/strong\u003e with white POM resin knob and \u003cstrong\u003ePTFE-sealed thread\u003c\/strong\u003e is rated to \u003cstrong\u003e10 bar and 100°C\u003c\/strong\u003e. The hygroscopic cartridge is \u003cstrong\u003efield-replaceable without draining the radiator\u003c\/strong\u003e, with a recommended service interval of 36 months.\u003c\/p\u003e\n\n\u003cdiv style=\"background:#008377CF; border-radius:6px; padding:18px 12px; display:flex; flex-wrap:wrap; justify-content:space-around; margin:18px 0;\"\u003e\n\u003cdiv style=\"text-align:center; padding:0 16px;\"\u003e\n\u003cdiv style=\"font-size:22px; font-weight:700; color:#fff;\"\u003e10 bar\u003c\/div\u003e\n\u003cdiv style=\"font-size:12px; color:#ddf4f2; text-transform:uppercase; letter-spacing:.5px;\"\u003eMax Pressure\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"text-align:center; padding:0 16px;\"\u003e\n\u003cdiv style=\"font-size:22px; font-weight:700; color:#fff;\"\u003e100°C\u003c\/div\u003e\n\u003cdiv style=\"font-size:12px; color:#ddf4f2; text-transform:uppercase; letter-spacing:.5px;\"\u003eMax Temp\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"text-align:center; padding:0 16px;\"\u003e\n\u003cdiv style=\"font-size:22px; font-weight:700; color:#fff;\"\u003e½\" BSP\u003c\/div\u003e\n\u003cdiv style=\"font-size:12px; color:#ddf4f2; text-transform:uppercase; letter-spacing:.5px;\"\u003eMale Thread\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"text-align:center; padding:0 16px;\"\u003e\n\u003cdiv style=\"font-size:22px; font-weight:700; color:#fff;\"\u003e36 months\u003c\/div\u003e\n\u003cdiv style=\"font-size:12px; color:#ddf4f2; text-transform:uppercase; letter-spacing:.5px;\"\u003eCartridge Life\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"text-align:center; padding:0 16px;\"\u003e\n\u003cdiv style=\"font-size:22px; font-weight:700; color:#fff;\"\u003eAuto + Manual\u003c\/div\u003e\n\u003cdiv style=\"font-size:12px; color:#ddf4f2; text-transform:uppercase; letter-spacing:.5px;\"\u003eDual Mode\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv style=\"border-left:4px solid #008377; background:#f0faf9; border-top:1px solid #b2e0db; border-right:1px solid #b2e0db; border-bottom:1px solid #b2e0db; border-radius:0 6px 6px 0; padding:12px 16px; margin:10px 0;\"\u003e\n\u003cstrong style=\"color:#008377;\"\u003eHow the Hygroscopic Mechanism Works\u003c\/strong\u003e\u003cbr\u003eInside the vent body is a cartridge of \u003cstrong\u003ecellulose fibre discs\u003c\/strong\u003e. These discs swell by 50% on contact with water, sealing the vent outlet against water loss. When air accumulates and the discs are exposed to air (dry conditions), they contract — opening the vent and allowing air to escape. Drying time decreases with higher water temperature: at 100°C the discs re-seal in as little as 15 minutes.\u003c\/div\u003e\n\u003cdiv style=\"border-left:4px solid #b7660a; background:#fffbf0; border-top:1px solid #ffe6b3; border-right:1px solid #ffe6b3; border-bottom:1px solid #ffe6b3; border-radius:0 6px 6px 0; padding:12px 16px; margin:10px 0;\"\u003e\n\u003cstrong style=\"color:#b7660a;\"\u003eCartridge Replacement Interval\u003c\/strong\u003e\u003cbr\u003eThe hygroscopic disc cartridge must be replaced \u003cstrong\u003eat least every 36 months\u003c\/strong\u003e, and more frequently on systems with hard or unfiltered water. The cartridge design allows in-situ replacement \u003cstrong\u003ewithout emptying the radiator\u003c\/strong\u003e.\u003c\/div\u003e\n\u003cdiv style=\"border-left:4px solid #c0392b; background:#fff5f5; border-top:1px solid #ffd5d5; border-right:1px solid #ffd5d5; border-bottom:1px solid #ffd5d5; border-radius:0 6px 6px 0; padding:12px 16px; margin:10px 0;\"\u003e\n\u003cstrong style=\"color:#c0392b;\"\u003eInstallation Orientation\u003c\/strong\u003e\u003cbr\u003eMust be installed \u003cstrong\u003evertically upright\u003c\/strong\u003e. The hygroscopic discs require vertical installation to function correctly. Do not install at an angle or horizontally.\u003c\/div\u003e\n\n\u003cdiv style=\"font-size:18px; font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:6px; margin:24px 0 12px 0;\"\u003eKey Features\u003c\/div\u003e\n\u003cdiv style=\"display:flex; flex-wrap:wrap; gap:14px; margin:18px 0;\"\u003e\n\u003cdiv style=\"flex:1 1 260px; min-width:220px;\"\u003e\u003cdiv style=\"border:1px solid #e0e0e0; border-radius:8px; padding:16px; background:#fff;\"\u003e\n\u003cdiv style=\"font-size:24px; margin-bottom:8px;\"\u003e🌿\u003c\/div\u003e\n\u003cdiv style=\"font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:4px; margin-bottom:8px;\"\u003ePassive Hygroscopic Venting\u003c\/div\u003e\n\u003cdiv style=\"font-size:15px; color:#444;\"\u003eNo float, no electrical components — just cellulose discs that respond to moisture. \u003cstrong\u003eAutomatically seals on water contact\u003c\/strong\u003e and opens when air displaces water, with no mechanical parts to jam or corrode.\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 260px; min-width:220px;\"\u003e\u003cdiv style=\"border:1px solid #e0e0e0; border-radius:8px; padding:16px; background:#fff;\"\u003e\n\u003cdiv style=\"font-size:24px; margin-bottom:8px;\"\u003e🔧\u003c\/div\u003e\n\u003cdiv style=\"font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:4px; margin-bottom:8px;\"\u003eManual Override\u003c\/div\u003e\n\u003cdiv style=\"font-size:15px; color:#444;\"\u003eRotating the white POM knob approximately one turn anti-clockwise activates \u003cstrong\u003emanual bleed mode\u003c\/strong\u003e — essential during initial system fill or when large air volumes require rapid purging.\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 260px; min-width:220px;\"\u003e\u003cdiv style=\"border:1px solid #e0e0e0; border-radius:8px; padding:16px; background:#fff;\"\u003e\n\u003cdiv style=\"font-size:24px; margin-bottom:8px;\"\u003e🔩\u003c\/div\u003e\n\u003cdiv style=\"font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:4px; margin-bottom:8px;\"\u003eReplaceable Cartridge\u003c\/div\u003e\n\u003cdiv style=\"font-size:15px; color:#444;\"\u003eThe hygroscopic cartridge assembly can be removed and replaced \u003cstrong\u003ein situ, without draining the radiator\u003c\/strong\u003e. A significant practical advantage over non-serviceable vent valves.\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 260px; min-width:220px;\"\u003e\u003cdiv style=\"border:1px solid #e0e0e0; border-radius:8px; padding:16px; background:#fff;\"\u003e\n\u003cdiv style=\"font-size:24px; margin-bottom:8px;\"\u003e🏗\u003c\/div\u003e\n\u003cdiv style=\"font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:4px; margin-bottom:8px;\"\u003eQuality Construction\u003c\/div\u003e\n\u003cdiv style=\"font-size:15px; color:#444;\"\u003eNickel-plated brass body, white heat-resistant POM knob, and PTFE-sealed thread — \u003cstrong\u003econsistent with Caleffi's wider manual radiator valve range\u003c\/strong\u003e for a uniform radiator connection finish.\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv style=\"margin:18px 0;\"\u003e\n\u003cdiv style=\"background:#008377CF; color:#fff; font-weight:700; padding:10px 14px; border-radius:6px 6px 0 0;\"\u003eTechnical Specifications\u003c\/div\u003e\n\u003ctable style=\"width:100%; border-collapse:collapse; border:1px solid #d0eeec;\"\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eMPN\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003e508041\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eSeries\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003e5080 — Hygroscopic Automatic Radiator Air Vent\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eConnection\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003e½\" BSP Male (external thread)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eBody Material\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003eBrass EN 12164 CW614N, nickel plated\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eKnob\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003eWhite POM (acetal resin), heat-resistant\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eThread Seal\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003ePTFE\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eMax Working Pressure\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003e10 bar\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eMax Working Temperature\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003e100°C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eVenting Principle\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003eHygroscopic cellulose fibre discs — auto and manual modes\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eDisc Expansion\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003e+50% volume when immersed in water\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eAuto Mode\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003eKnob fully closed — vent opens when dry, seals when wet\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eManual Mode\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003eKnob rotated ~1 turn anti-clockwise\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eCartridge\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003eReplaceable; service interval minimum 36 months\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eInstallation\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003eVertical upright only\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#f4fcfb;\"\u003eOther Sizes Available\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#f4fcfb;\"\u003e508011 (1\/8\"); 508021 (1\/4\"); 508031 (3\/8\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px 12px; width:50%; font-weight:600; background:#fff;\"\u003eManufacturer\u003c\/td\u003e\n\u003ctd style=\"padding:8px 12px; background:#fff;\"\u003eCaleffi S.p.A., Italy\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003cdiv style=\"font-size:18px; font-weight:700; color:#008377; border-bottom:2px solid #008377; padding-bottom:6px; margin:24px 0 12px 0;\"\u003eFrequently Asked Questions\u003c\/div\u003e\n\u003cdiv style=\"margin:18px 0;\"\u003e\n\u003cdetails style=\"border:1px solid #d0eeec; border-radius:6px; margin-bottom:8px; overflow:hidden;\"\u003e\u003csummary style=\"background:#008377CF; color:#fff; padding:12px 16px; cursor:pointer; font-weight:600; list-style:none;\"\u003eHow is a hygroscopic vent different from a float-type automatic air vent?\u003c\/summary\u003e\u003cdiv style=\"padding:14px 16px; background:#f9fefe; font-size:15px;\"\u003eA hygroscopic vent uses cellulose discs that physically swell and shrink with moisture content to open and close the vent — no float, no moving mechanical parts beyond the knob. Float-type vents (such as the Caleffi Robocal) use a rising float to seal a valve outlet. Hygroscopic vents have a smaller body profile suited to radiator bleed points, while float vents are typically installed in-line on pipework high points.\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #d0eeec; border-radius:6px; margin-bottom:8px; overflow:hidden;\"\u003e\u003csummary style=\"background:#008377CF; color:#fff; padding:12px 16px; cursor:pointer; font-weight:600; list-style:none;\"\u003eHow do I know when the cartridge needs replacing?\u003c\/summary\u003e\u003cdiv style=\"padding:14px 16px; background:#f9fefe; font-size:15px;\"\u003eSigns of cartridge failure include water dripping from the vent outlet without air being present (discs no longer sealing), or the system failing to auto-vent trapped air. Caleffi recommends proactive replacement every 36 months regardless of apparent condition — more frequently if the system uses hard or unfiltered water.\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #d0eeec; border-radius:6px; margin-bottom:8px; overflow:hidden;\"\u003e\u003csummary style=\"background:#008377CF; color:#fff; padding:12px 16px; cursor:pointer; font-weight:600; list-style:none;\"\u003eWhat thread does my radiator need for this vent?\u003c\/summary\u003e\u003cdiv style=\"padding:14px 16px; background:#f9fefe; font-size:15px;\"\u003eMPN 508041 has a ½\" BSP male (external) thread. The vast majority of UK panel and column radiators have a ½\" BSP female bleed port at the top-end of the radiator — this is the standard direct fit.\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #d0eeec; border-radius:6px; margin-bottom:8px; overflow:hidden;\"\u003e\u003csummary style=\"background:#008377CF; color:#fff; padding:12px 16px; cursor:pointer; font-weight:600; list-style:none;\"\u003eIs this suitable for pressurised sealed heating systems?\u003c\/summary\u003e\u003cdiv style=\"padding:14px 16px; background:#f9fefe; font-size:15px;\"\u003eYes. The 10 bar maximum working pressure rating is well above the typical 1–2.5 bar operating pressure of UK sealed heating systems.\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #d0eeec; border-radius:6px; margin-bottom:8px; overflow:hidden;\"\u003e\u003csummary style=\"background:#008377CF; color:#fff; padding:12px 16px; cursor:pointer; font-weight:600; list-style:none;\"\u003eCan this vent be installed as a permanent automatic vent without manual intervention?\u003c\/summary\u003e\u003cdiv style=\"padding:14px 16px; background:#f9fefe; font-size:15px;\"\u003eYes — with the knob fully closed (automatic mode), the vent operates passively. Manual intervention is only needed during initial fill or when rapid large-volume air purging is required.\u003c\/div\u003e\u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e","brand":"Caleffi","offers":[{"title":"Default Title","offer_id":64954922893661,"sku":"508041","price":9.95,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0958\/2051\/3629\/files\/CaleffiSeries5080HygroscopicAutomaticRadiatorAirVent508041HalfInchBSP.jpg?v=1781189452","url":"https:\/\/qualityheating.co.uk\/products\/caleffi-series-5080-hygroscopic-automatic-radiator-air-vent-508041-half-inch-bsp","provider":"AIZO Quality Heating","version":"1.0","type":"link"}