{"product_id":"zilmet-hydro-pro-2-litre-potable-expansion-vessel-11a0000200-bsp","title":"Zilmet Hydro-Pro 2 Litre Potable Expansion Vessel – 11A0000200 – ½\" BSP","description":"\u003c!-- SEO Product Name: Zilmet Hydro-Pro 2 Litre Potable Expansion Vessel – 11A0000200 – ½\" BSP --\u003e\n\u003cdiv style=\"font-family: Arial, sans-serif; color: #1a1a1a; max-width: 900px; line-height: 1.7;\"\u003e\n\u003c!-- Intro --\u003e\n\u003cp style=\"font-size: 15px;\"\u003eThe \u003cstrong\u003eZilmet Hydro-Pro 2\u003c\/strong\u003e is a 2-litre potable expansion vessel designed for domestic hot water systems, unvented cylinders, water heaters, pump sets, and anti-water-hammer applications.\u003c\/p\u003e\n\u003cp style=\"font-size: 15px;\"\u003eThe vessel uses a \u003cstrong\u003efixed Zilan DW diaphragm membrane\u003c\/strong\u003e — not a bladder — which isolates system water from the pre-charged air chamber. The membrane's seamless shape has no corners or creases where stagnant water or sediment can collect, actively \u003cstrong\u003einhibiting bacteriological growth\u003c\/strong\u003e and keeping the system hygienic. The carbon steel shell is finished internally with an exclusive epoxy powder coating and externally with an epoxy-polyester paint — both providing long-term corrosion resistance.\u003c\/p\u003e\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;\"\u003eMPN: 11A0000200\u003c\/span\u003e \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eWRAS Approved\u003c\/span\u003e \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003eNSF \/ IAPMO \/ ACS\u003c\/span\u003e \u003cspan style=\"background: #008377CF; color: #fff; padding: 7px 13px; border-radius: 20px; font-size: 12px; font-weight: bold;\"\u003e10 Bar Max\u003c\/span\u003e \u003c\/div\u003e\n\u003c!-- Technical specifications --\u003e\n\u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; font-size: 14px; margin-bottom: 24px;\"\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;\"\u003eValue\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 \/ Product code\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e11A0000200\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eVessel volume\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e2 litres\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;\"\u003e½\" BSP male (G½\")\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMax operating pressure\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e10 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;\"\u003eOperating temperature range\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e-10°C to +99°C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eFactory pre-charge pressure\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e3.5 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;\"\u003eShell material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eCarbon steel — deep-drawn, MIG welded\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eInternal coating\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eExclusive epoxy powder coating — corrosion resistant\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;\"\u003eExternal finish\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eEpoxy-polyester paint — rust resistant — blue\/grey\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eMembrane type\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eFixed Zilan DW diaphragm — food-grade, potable water approved\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 fitting material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003eCarbon steel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eDiameter (ØD)\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e142mm\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;\"\u003eHeight (H)\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e196mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3; font-weight: bold;\"\u003eDrawdown @ Pmax 10 Bar\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003e1.2 litres (heating) \/ 1.1 litres @ 0.8 L\/min (pump duty)\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;\"\u003eCertifications\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 12px; border: 1px solid #c8e6e3;\"\u003ePED 2014\/68\/EU · WRAS · ACS · IAPMO · NSF\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;\"\u003eZilmet SpA, Limena, Padova, Italy\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\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\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;\"\u003eWRAS-approved potable water use\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eHolds international approvals for use with drinking water including WRAS (UK Water Regulations Advisory Scheme), ACS (France), IAPMO, and NSF. The Zilan DW fixed diaphragm membrane and internal epoxy coating are food-grade rated — suitable for unvented hot water cylinder installations and mains pressure systems.\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;\"\u003eFixed Zilan DW diaphragm — no stagnation\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eThe fixed diaphragm design has no creases, corners, or dead zones where water can stagnate. This seamless geometry actively inhibits bacteriological growth — important in any potable water application. Water and air are completely separated at all times; no waterlogging or pressure loss through air absorption.\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;\"\u003eExclusive MIG welded construction\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eZilmet's exclusive deep-drawn MIG welding process eliminates all interior sharp edges, rough spots, and weld profiles. This protects the diaphragm from damage over the life of the vessel and ensures the internal epoxy coating bonds uniformly across the entire shell — preventing localised corrosion.\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 pre-charged and tested\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eEvery Hydro-Pro 2 leaves the Zilmet factory pre-charged to \u003cstrong\u003e3.5 Bar\u003c\/strong\u003e and individually pressure-tested. The pre-charge valve is fitted with a protective cap. Pre-charge can be adjusted on site with a standard Schrader valve pump if the system static pressure requires a different setting.\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 — 142mm diameter × 196mm height\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eAt 142mm diameter and 196mm tall, the Hydro-Pro 2 fits easily in the airing cupboard next to an unvented cylinder or in a tight boiler cupboard. The ½\" BSP male connection is standard across virtually all unvented cylinder expansion vessel connections and cold water expansion fittings.\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;\"\u003eAnti-water-hammer protection\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px;\"\u003eIn addition to thermal expansion duty, the Hydro-Pro 2 absorbs the pressure spikes caused by rapid valve closure and pump stop\/start cycles — protecting downstream components, fittings, and appliances from shock damage. Suitable for installation on pump sets, boosters, and solenoid-valve-controlled circuits.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- Application \/ sizing guidance --\u003e\n\u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eApplications \u0026amp; Sizing Guidance\u003c\/h2\u003e\n\u003cp style=\"font-size: 14px;\"\u003eThe Hydro-Pro 2 is sized for small domestic applications where a compact vessel is required. Typical uses include thermal expansion relief on unvented hot water cylinders up to approximately 150 litres (at typical UK mains pressures), cold water expansion on combination boiler systems, and anti-water-hammer damping on pump sets and motorised valve circuits.\u003c\/p\u003e\n\u003cp style=\"font-size: 14px;\"\u003eThe correct vessel size for a given installation depends on the system volume, maximum working pressure, minimum static pressure, and temperature range. The pre-charge pressure should be set equal to the cold static fill pressure of the system. Zilmet publish a full drawdown and sizing calculator at their website. \u003cstrong\u003eVessel sizing must be verified by a competent installer or engineer.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cdiv style=\"background: #f0faf9; border-left: 4px solid #008377CF; padding: 12px 16px; margin: 14px 0 24px; font-size: 14px; border-radius: 0 4px 4px 0;\"\u003e\n\u003cstrong style=\"color: #008377cf;\"\u003ePre-charge and drawdown data for Hydro-Pro 2:\u003c\/strong\u003e Factory pre-charge 3.5 Bar. Drawdown at Pmax 4–5 Bar: 0.4 litres (pump) \/ 0.5 litres (heating). Drawdown at Pmax 6–7 Bar: 0.8 litres (pump) \/ 0.9 litres (heating). Drawdown at Pmax 8–9 Bar: 1.0 litres (pump) \/ 1.1 litres (heating). Drawdown at Pmax 10 Bar: 1.1 litres (pump) \/ 1.2 litres (heating).\u003c\/div\u003e\n\u003c!-- Installation notes --\u003e\n\u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eInstallation Notes\u003c\/h2\u003e\n\u003cp style=\"font-size: 14px;\"\u003eThe Hydro-Pro 2 can be installed in any orientation — vertically (connection up or down) or horizontally — although vertical connection-up is preferred as it keeps the diaphragm correctly positioned over time. Install as close as possible to the appliance it is serving, with a suitable isolation valve and check valve upstream to prevent system pressure from affecting the pre-charge. For unvented cylinder duty, the vessel must comply with the G3 Building Regulation requirements for the installation; the vessel pressure rating must meet or exceed the maximum system pressure.\u003c\/p\u003e\n\u003cdiv style=\"background: #fff8e1; border-left: 4px solid #f59e0b; padding: 12px 16px; margin: 14px 0 24px; font-size: 14px; border-radius: 0 4px 4px 0;\"\u003e\n\u003cstrong style=\"color: #b45309;\"\u003eImportant:\u003c\/strong\u003e Always check and if necessary adjust the pre-charge pressure before filling the system. The pre-charge must equal the cold static fill pressure of the system — typically 1.0–3.5 Bar for domestic potable water. Do not pressurise beyond the vessel's 10 Bar rating. Expansion vessel sizing and installation on unvented systems must be carried out by a competent person under Part G of the Building Regulations.\u003c\/div\u003e\n\u003c!-- FAQ --\u003e\n\u003ch2 style=\"color: #fff; background: #008377CF; padding: 10px 16px; border-radius: 4px; font-size: 16px; margin: 28px 0 16px;\"\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv style=\"margin-bottom: 14px; border-left: 3px solid #008377CF; padding-left: 14px;\"\u003e\n\u003cp style=\"font-weight: bold; color: #008377cf; margin-bottom: 4px;\"\u003eIs the Hydro-Pro 2 suitable for an unvented hot water cylinder?\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 14px;\"\u003eYes — the Hydro-Pro 2 is WRAS approved for potable water use and rated to 10 Bar and 99°C, covering the operating conditions of domestic unvented cylinders. Confirm that the vessel capacity is correctly sized for the cylinder volume and system pressure range; for cylinders over approximately 150 litres a larger vessel will normally be required.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"margin-bottom: 14px; border-left: 3px solid #008377CF; padding-left: 14px;\"\u003e\n\u003cp style=\"font-weight: bold; color: #008377cf; margin-bottom: 4px;\"\u003eWhat is the factory pre-charge and can I adjust it?\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 14px;\"\u003eThe vessel leaves the factory pre-charged to 3.5 Bar. This is suitable for systems with a cold fill pressure up to 3.5 Bar. If your system cold fill pressure differs, adjust the pre-charge using a standard Schrader valve pump with the vessel isolated from the system and fully depressurised on the water side. Always set pre-charge equal to the cold static fill pressure before reconnecting.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"margin-bottom: 14px; border-left: 3px solid #008377CF; padding-left: 14px;\"\u003e\n\u003cp style=\"font-weight: bold; color: #008377cf; margin-bottom: 4px;\"\u003eWhat is the difference between a diaphragm vessel and a bladder vessel?\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 14px;\"\u003eIn a diaphragm vessel (like the Hydro-Pro), the membrane is fixed to the inside of the shell and divides the vessel into two chambers — water one side, air the other. In a bladder vessel the membrane is a free-floating bag. The Hydro-Pro's fixed diaphragm design means the membrane never creases or bunches, giving a longer service life and the seamless anti-stagnation geometry that makes it suitable for potable water duty.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"margin-bottom: 14px; border-left: 3px solid #008377CF; padding-left: 14px;\"\u003e\n\u003cp style=\"font-weight: bold; color: #008377cf; margin-bottom: 4px;\"\u003eHow do I know when the expansion vessel needs replacing?\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 14px;\"\u003eCommon signs of a failed expansion vessel include the pressure relief valve on the cylinder discharging regularly, rapid pressure fluctuations when hot water is drawn, or the vessel feeling completely hard with no give when tapped. Check the pre-charge pressure annually — if the vessel holds no pre-charge even after re-pressurising, the diaphragm has failed and the vessel should be replaced.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"margin-bottom: 14px; border-left: 3px solid #008377CF; padding-left: 14px;\"\u003e\n\u003cp style=\"font-weight: bold; color: #008377cf; margin-bottom: 4px;\"\u003eCan the Hydro-Pro 2 also be used for anti-water-hammer duty on a pump set?\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 14px;\"\u003eYes — the Hydro-Pro range is explicitly rated and sized for anti-water-hammer applications on electric pump sets. The pre-charged air chamber absorbs the pressure spike created by rapid valve closure or pump stop. At Pmax 10 Bar, the Hydro-Pro 2 provides a drawdown of 1.1 litres at up to 0.8 L\/min pump flow rate — sufficient for small domestic booster and pump applications.\u003c\/p\u003e\n\u003c\/div\u003e\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\u003eZilmet Hydro-Pro 5 Litre Potable Expansion Vessel | Zilmet Hydro-Pro 8 Litre Potable Expansion Vessel | Zilmet Hydro-Pro 12 Litre Potable Expansion Vessel | ½\" BSP Check Valve | Expansion Vessel Bracket | Pressure Reducing Valve 15mm | 6 Bar Pressure Relief Valve 15mm\u003c\/div\u003e\n\u003c\/div\u003e","brand":"Zilmet","offers":[{"title":"Default Title","offer_id":63899644100957,"sku":"11A0000200","price":27.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0958\/2051\/3629\/files\/Zilmet2LtrExpansionVesselPotableHydro-ProVessel11A0000200.webp?v=1773810352","url":"https:\/\/qualityheating.co.uk\/products\/zilmet-hydro-pro-2-litre-potable-expansion-vessel-11a0000200-bsp","provider":"AIZO Quality Heating","version":"1.0","type":"link"}