{"product_id":"gws-thermowave-twb-60lv-60-litre-vertical-potable-expansion-vessel","title":"GWS ThermoWave TWB-60LV 60 Litre Vertical Potable Expansion Vessel","description":"\u003cdiv style=\"font-size: 16px; font-family: Arial,Helvetica,sans-serif; color: #1a1a1a; max-width: 900px; margin: 0 auto; line-height: 1.6;\"\u003e\n\u003c!-- ── INTRO ─────────────────────────────────────────────────────── --\u003e\n\u003cp style=\"margin: 0 0 18px;\"\u003eThe \u003cstrong\u003eGlobal Water Solutions ThermoWave TWB-60LV\u003c\/strong\u003e is a \u003cstrong\u003e60-litre WRAS-approved vertical potable water expansion vessel\u003c\/strong\u003e designed for thermal expansion management in large domestic and light commercial \u003cstrong\u003eunvented hot water cylinder installations\u003c\/strong\u003e. As water is heated in a sealed system it expands — the ThermoWave vessel absorbs this expanded volume through a high-grade butyl diaphragm, preventing excess pressure from forcing water through the temperature and pressure relief valve and wasting energy. The vessel is factory \u003cstrong\u003epre-charged to 1.9 bar\u003c\/strong\u003e and connects via a \u003cstrong\u003e¾\" BSPT male connection\u003c\/strong\u003e. Constructed with a virgin polypropylene liner, patented stainless-steel water connection providing a dual water\/air seal, O-ring sealed air valve, and a corrosion-resistant carbon steel shell with dual-layer polyurethane coating. Maximum working pressure \u003cstrong\u003e10 bar\u003c\/strong\u003e; maximum temperature \u003cstrong\u003e90°C\u003c\/strong\u003e. \u003cstrong\u003eWRAS approved for potable water\u003c\/strong\u003e, fully maintenance-free, and backed by a \u003cstrong\u003e5-year warranty\u003c\/strong\u003e.\u003c\/p\u003e\n\u003c!-- ── TEAL APPLICATION CALLOUT ──────────────────────────────────── --\u003e\n\u003cdiv style=\"border-left: 4px solid #008377CF; background: #e6f4f3; padding: 10px 16px; margin-bottom: 22px; border-radius: 0 6px 6px 0;\"\u003e\n\u003cstrong style=\"color: #005c54;\"\u003eℹ Unvented Cylinders \u0026amp; Expansion Vessels — Why You Need One\u003c\/strong\u003e\u003cbr\u003eUnvented hot water cylinders operate at mains pressure in a sealed system. When water is heated, it expands — a 60-litre cylinder of cold water at 10°C expands by approximately 1.5 litres when heated to 60°C. Without an expansion vessel, this expanded volume has nowhere to go and the system pressure rises until the \u003cstrong\u003etemperature and pressure relief valve (T\u0026amp;P ERV)\u003c\/strong\u003e discharges water to waste. A correctly sized expansion vessel absorbs the expansion silently and maintains system pressure within limits, preventing continuous relief valve cycling, conserving water, and protecting system components. Building Regulations Part G and the Water Supply (Water Fittings) Regulations 1999 require an approved expansion vessel in every unvented hot water installation.\u003c\/div\u003e\n\u003c!-- ── RED INSTALLATION NOTE ─────────────────────────────────────── --\u003e\n\u003cdiv style=\"border-left: 4px solid #c0392b; background: #fff5f5; padding: 10px 16px; margin-bottom: 22px; border-radius: 0 6px 6px 0;\"\u003e\n\u003cstrong style=\"color: #c0392b;\"\u003e⚠ G3 Qualified Installation Required\u003c\/strong\u003e — Unvented hot water systems including expansion vessels must be installed, commissioned, and maintained by a \u003cstrong\u003eG3 (Unvented Hot Water Storage) qualified competent person\u003c\/strong\u003e. The installation must be notified to Building Control. The vessel pre-charge pressure must be verified against the incoming mains pressure and cylinder working pressure before commissioning — an incorrectly charged vessel will not function correctly. Fixings are not included.\u003c\/div\u003e\n\u003c!-- ── STAT STRIP ─────────────────────────────────────────────────── --\u003e\n\u003cdiv style=\"display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 20px;\"\u003e\n\u003cdiv style=\"flex: 1; min-width: 90px; background: #008377CF; color: #fff; border-radius: 6px; padding: 11px 8px; text-align: center;\"\u003e\n\u003cdiv style=\"font-size: 17px; font-weight: bold;\"\u003e60 litres\u003c\/div\u003e\n\u003cdiv style=\"font-size: 12px; margin-top: 3px;\"\u003eCapacity\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex: 1; min-width: 90px; background: #008377CF; color: #fff; border-radius: 6px; padding: 11px 8px; text-align: center;\"\u003e\n\u003cdiv style=\"font-size: 17px; font-weight: bold;\"\u003e10 bar\u003c\/div\u003e\n\u003cdiv style=\"font-size: 12px; margin-top: 3px;\"\u003eMax pressure\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex: 1; min-width: 90px; background: #008377CF; color: #fff; border-radius: 6px; padding: 11px 8px; text-align: center;\"\u003e\n\u003cdiv style=\"font-size: 17px; font-weight: bold;\"\u003e90°C\u003c\/div\u003e\n\u003cdiv style=\"font-size: 12px; margin-top: 3px;\"\u003eMax temperature\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex: 1; min-width: 90px; background: #008377CF; color: #fff; border-radius: 6px; padding: 11px 8px; text-align: center;\"\u003e\n\u003cdiv style=\"font-size: 17px; font-weight: bold;\"\u003eWRAS\u003c\/div\u003e\n\u003cdiv style=\"font-size: 12px; margin-top: 3px;\"\u003ePotable approved\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex: 1; min-width: 90px; background: #008377CF; color: #fff; border-radius: 6px; padding: 11px 8px; text-align: center;\"\u003e\n\u003cdiv style=\"font-size: 17px; font-weight: bold;\"\u003e5 years\u003c\/div\u003e\n\u003cdiv style=\"font-size: 12px; margin-top: 3px;\"\u003eWarranty\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- ── FEATURES GRID ──────────────────────────────────────────────── --\u003e\n\u003cdiv style=\"background: #008377CF; color: #fff; font-weight: 600; font-size: 15px; padding: 10px 16px; border-radius: 6px 6px 0 0;\"\u003eFeatures \u0026amp; Benefits\u003c\/div\u003e\n\u003cdiv style=\"display: grid; grid-template-columns: repeat(auto-fill,minmax(255px,1fr)); gap: 12px; background: #e6f4f3; padding: 14px; border-radius: 0 0 6px 6px; margin-bottom: 22px;\"\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ WRAS Approved — Safe for Potable Water\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003e\n\u003cstrong\u003eWRAS (Water Regulations Advisory Scheme) approval\u003c\/strong\u003e confirms that the ThermoWave vessel meets the requirements of the Water Supply (Water Fittings) Regulations 1999 for contact with drinking water. This is a \u003cstrong\u003emandatory requirement\u003c\/strong\u003e for expansion vessels installed on unvented hot water cylinders in the UK — only WRAS-approved vessels may legally be used in systems connected to the potable supply. The vessel's \u003cstrong\u003evirgin polypropylene liner and butyl diaphragm\u003c\/strong\u003e are materials approved for continuous contact with drinking water, ensuring the potable supply remains safe and uncontaminated.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ High-Grade Butyl Diaphragm — Virgin Polypropylene Liner\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003eThe \u003cstrong\u003ehigh-grade butyl diaphragm\u003c\/strong\u003e is flexible, durable, and impermeable to air — it maintains the air charge separation from the potable water side for the life of the vessel without gradual pressure loss. Butyl is one of the most resistant elastomers to water, heat, and oxidation, making it the material of choice for long-life expansion vessels in hot water applications up to 90°C. The \u003cstrong\u003evirgin polypropylene liner\u003c\/strong\u003e on the water side provides a chemically inert, non-leaching surface in contact with the potable supply, with no risk of metallic contamination or taste transfer to the water.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ Patented Stainless Steel Connection — Dual Water\/Air Seal\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003eThe \u003cstrong\u003epatented stainless-steel water connection\u003c\/strong\u003e provides a \u003cstrong\u003edual water\/air seal\u003c\/strong\u003e — the connection seals against both the water pressure from the system side and the air pressure from the gas side simultaneously. This design eliminates the risk of air migrating into the water circuit or water entering the gas chamber through the connection point — one of the most common failure modes on conventional expansion vessels with brass or plastic connections. The stainless-steel construction is also resistant to dezincification and chloride corrosion in hard and treated water systems.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ O-Ring Sealed Air Valve — Maintenance Free\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003eThe \u003cstrong\u003eO-ring sealed air valve cap\u003c\/strong\u003e prevents air pressure loss from the gas side of the vessel over time — a common cause of expansion vessel failure on older designs where the Schrader-type valve gradually seeps air. The sealed cap design means the \u003cstrong\u003evessel is fully maintenance free\u003c\/strong\u003e in normal operation: the air charge is set at manufacture and maintained for the product's service life without periodic top-up. There is no rubber valve core to replace and no need for annual pressure checks on the gas side during routine cylinder servicing.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ Carbon Steel Shell — Dual-Layer Polyurethane Coating\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003eThe \u003cstrong\u003ecarbon steel shell\u003c\/strong\u003e is protected externally by a \u003cstrong\u003edual-layer polyurethane paint system over an epoxy primer\u003c\/strong\u003e — the same coating approach used in GWS's other pressure vessel ranges, providing hundreds of hours of UV and salt spray resistance in independent testing. This protects the vessel against surface rust in damp plant rooms, airing cupboards, and garage installations where humidity is higher than in a dry living space. The coating is applied to the fully formed vessel after manufacture, ensuring complete coverage including welds and joints.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f0faf9; border: 1px solid #c8e6e3; border-radius: 6px; padding: 13px;\"\u003e\n\u003cdiv style=\"font-weight: bold; color: #008377cf; margin-bottom: 5px;\"\u003e✔ Pre-Charged 1.9 bar — ¾\" BSPT Connection\u003c\/div\u003e\n\u003cdiv style=\"font-size: 14px;\"\u003eFactory \u003cstrong\u003epre-charged to 1.9 bar (28 psi)\u003c\/strong\u003e, matching the standard mains supply cold pressure in most UK residential installations. The ¾\" connection is the most common size used for cylinder expansion vessel tails, allowing direct connection without reducers in the majority of unvented cylinder installations. As with all expansion vessels, the installer must \u003cstrong\u003everify the pre-charge pressure matches the static cold fill pressure of the system\u003c\/strong\u003e before commissioning — the vessel charge should equal the cold fill pressure, typically the mains static pressure at the vessel connection point. Re-charge via the Schrader valve on the air side if adjustment is needed.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- ── SPEC TABLE ─────────────────────────────────────────────────── --\u003e\n\u003cdiv style=\"background: #008377CF; color: #fff; font-weight: 600; font-size: 15px; padding: 10px 16px; border-radius: 6px 6px 0 0;\"\u003eTechnical Specifications — ThermoWave TWB-60LV\u003c\/div\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; margin-bottom: 22px; font-size: 14px;\"\u003e\n\u003ctbody\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; width: 44%; border-bottom: 1px solid #c8e6e3;\"\u003eManufacturer \/ MPN\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eGlobal Water Solutions (GWS) — \u003cstrong\u003eTWB-60LV\u003c\/strong\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eRange\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eThermoWave™ — potable hot water expansion vessel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eEAN\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e5055916801048\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eCapacity\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e\u003cstrong\u003e60 litres\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eOrientation\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eVertical (LV)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eConnection\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e¾\" BSPT male\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eFactory Pre-Charge\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003cstrong\u003e1.9 bar\u003c\/strong\u003e (28 psi)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eMax. Working Pressure\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e\u003cstrong\u003e10 bar\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eMax. Working Temperature\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e\u003cstrong\u003e90°C\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eDiaphragm Material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eHigh-grade butyl\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eLiner Material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eVirgin polypropylene (potable water safe)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eWater Connection Material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eStainless steel — patented dual water\/air seal\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eShell Material\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eCarbon steel — dual-layer polyurethane over epoxy primer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eAir Valve\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eO-ring sealed — leak-free, maintenance free\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eGross Weight (inc. packaging)\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003eapprox. 11.6 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #fff;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600; border-bottom: 1px solid #c8e6e3;\"\u003eApprovals\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px; border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003cstrong\u003eWRAS approved\u003c\/strong\u003e (potable water); CE\/PED; ISO 9001\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background: #f0faf9;\"\u003e\n\u003ctd style=\"padding: 9px 14px; font-weight: 600;\"\u003eWarranty\u003c\/td\u003e\n\u003ctd style=\"padding: 9px 14px;\"\u003e\n\u003cstrong\u003e5 years\u003c\/strong\u003e (GWS manufacturer's warranty)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c!-- ── FAQ ────────────────────────────────────────────────────────── --\u003e\n\u003cdiv style=\"background: #008377CF; color: #fff; font-weight: 600; font-size: 15px; padding: 10px 16px; border-radius: 6px 6px 0 0;\"\u003eFrequently Asked Questions\u003c\/div\u003e\n\u003cdiv style=\"border: 1px solid #c8e6e3; border-top: none; border-radius: 0 0 6px 6px; margin-bottom: 8px;\"\u003e\n\u003cdetails style=\"border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003csummary style=\"padding: 13px 16px; cursor: pointer; font-weight: 600; background: #f0faf9;\"\u003eWhat size expansion vessel do I need for my unvented cylinder?\u003c\/summary\u003e\n\u003cdiv style=\"padding: 11px 16px; font-size: 14px;\"\u003eExpansion vessel sizing depends on four factors: \u003cstrong\u003ethe cylinder storage volume, the cold fill (mains) pressure, the maximum working pressure of the system, and the heating temperature\u003c\/strong\u003e. As a rough guide, a 60-litre expansion vessel is typically appropriate for unvented cylinders between approximately 180–300 litres with standard mains pressures of 2–4 bar. The G3-qualified installer is responsible for correctly sizing the vessel using the calculation in BS 7206 or the cylinder manufacturer's installation manual — an incorrectly sized vessel will either not absorb sufficient expansion (leading to repeated T\u0026amp;P valve discharge) or be unnecessarily large. GWS provides a tank sizing calculator on their website for guidance, but the final selection must be validated by the installer.\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails style=\"border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003csummary style=\"padding: 13px 16px; cursor: pointer; font-weight: 600; background: #fff;\"\u003eHow do I set the correct pre-charge pressure?\u003c\/summary\u003e\n\u003cdiv style=\"padding: 11px 16px; font-size: 14px;\"\u003eThe vessel is factory pre-charged to 1.9 bar, which suits most UK residential mains supplies at typical static pressures. To verify and adjust: \u003cstrong\u003e1)\u003c\/strong\u003e Isolate the vessel from the water system and release all water pressure from the system side of the vessel. \u003cstrong\u003e2)\u003c\/strong\u003e Check the gas-side pressure using a tyre gauge on the Schrader valve. \u003cstrong\u003e3)\u003c\/strong\u003e The correct pre-charge should equal the \u003cstrong\u003ecold static fill pressure of the system at the vessel connection point\u003c\/strong\u003e — typically the mains static pressure at the vessel. If the mains pressure is 3 bar, set the vessel to 3 bar. If the vessel pre-charge is too low, it will be partly compressed by cold water and have insufficient expansion capacity; if too high, it will remain uninflated and the system will hit the expansion relief valve at lower temperatures. Re-charge using a bicycle pump or compressor via the Schrader valve if adjustment is needed.\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails style=\"border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003csummary style=\"padding: 13px 16px; cursor: pointer; font-weight: 600; background: #f0faf9;\"\u003eWhy does my expansion vessel need to be WRAS approved?\u003c\/summary\u003e\n\u003cdiv style=\"padding: 11px 16px; font-size: 14px;\"\u003eUnder the \u003cstrong\u003eWater Supply (Water Fittings) Regulations 1999\u003c\/strong\u003e (England and Wales), any fitting, material, or device connected to the potable (drinking) water supply must be of a type approved or acceptable under the regulations. For expansion vessels, this means WRAS approval — which certifies that the vessel's materials (liner, diaphragm, connection) do not leach harmful substances into the drinking water, cannot contaminate the supply, and are physically suitable for the pressures and temperatures encountered. \u003cstrong\u003eUsing a non-WRAS expansion vessel on a potable system is a breach of the Water Fittings Regulations\u003c\/strong\u003e and could invalidate the installation's Building Control notification and the cylinder manufacturer's warranty. The TWB-60LV carries full WRAS approval.\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails style=\"border-bottom: 1px solid #c8e6e3;\"\u003e\n\u003csummary style=\"padding: 13px 16px; cursor: pointer; font-weight: 600; background: #fff;\"\u003eHow do I know if my expansion vessel has failed and needs replacing?\u003c\/summary\u003e\n\u003cdiv style=\"padding: 11px 16px; font-size: 14px;\"\u003eThe most common signs of a failed expansion vessel are: \u003cstrong\u003e(a) the T\u0026amp;P relief valve repeatedly discharges\u003c\/strong\u003e small amounts of water — the expanding water has nowhere to go because the vessel is waterlogged; \u003cstrong\u003e(b) the system pressure rises rapidly when the cylinder heats up\u003c\/strong\u003e — visible on the pressure gauge on the unvented kit; \u003cstrong\u003e(c) the vessel feels completely full of water\u003c\/strong\u003e — a healthy vessel should have some give when tapped; it should feel partly hollow. The most definitive test is to check the gas-side pressure when the system is cold and depressurised: if there is no air pressure at all (the gas has fully leaked or the diaphragm has ruptured), the vessel needs replacement. Annual servicing of the unvented system by a G3 competent person should include checking the expansion vessel condition.\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary style=\"padding: 13px 16px; cursor: pointer; font-weight: 600; background: #f0faf9;\"\u003eCan this expansion vessel be used on a heating (non-potable) system?\u003c\/summary\u003e\n\u003cdiv style=\"padding: 11px 16px; font-size: 14px;\"\u003eThe ThermoWave range is \u003cstrong\u003especifically designed and approved for potable water systems\u003c\/strong\u003e — the WRAS approval, polypropylene liner, and butyl diaphragm are specified for drinking water contact. It can be used on a heating circuit (central heating expansion), but a standard heating expansion vessel (typically red, with an EPDM diaphragm and no polypropylene liner) would be the more cost-effective and appropriate choice for a non-potable application. Heating system water contains inhibitor chemicals that are not present in a potable system, and the vessel does not need to be WRAS approved for heating use. Using a potable-rated vessel on a heating system is not harmful, but you would be paying for WRAS approval you do not need. For unvented cylinder installations, always use the WRAS-approved potable vessel.\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e","brand":"Global Water Solutions","offers":[{"title":"Default Title","offer_id":64186767212893,"sku":"TWB-60LV","price":99.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0958\/2051\/3629\/files\/GWSTWB-60LVThermoWave60LitrePotableVerticalExpansionVessel.webp?v=1776181647","url":"https:\/\/qualityheating.co.uk\/products\/gws-thermowave-twb-60lv-60-litre-vertical-potable-expansion-vessel","provider":"AIZO Quality Heating","version":"1.0","type":"link"}