St AlbansMon–Sat 8:00–17:30 · 24/7 Emergency · Gas Safe Registered info@heatrite.uk07455 74863507702 52346407584 076105 About Domestic Commercial Service Areas Our WorkContact07455 748635 Request Estimate Cylinders · G3 certified · Hertfordshire # Vented & Unvented Cylinder Installation Mains-pressure hot water to every tap, sized for your actual demand, installed, certified and commissioned by G3-qualified engineers. Get my cylinder quote 07455 74863507702 523464 G3 certificate issued on completion · Megaflo, Telford & Heatrae Sadia · 25-year cylinder warranty options - G3 unvented qualified - Gas Safe registered (Co. 15149175) - Megaflo, Telford & Heatrae Sadia - 25-year cylinder warranty options - Fully insured to £5m Service overview ## What vented & unvented hot water cylinders actually involves. Plain-English breakdown, so you know exactly what you're paying for, and why it matters before we set foot on site. ### What it is Supply, install, swap and service vented (open-vent) and unvented (mains-pressure) hot water cylinders across St Albans and Hertfordshire. Includes pipework, expansion vessel, tundish, discharge route, immersion wiring and G3 commissioning paperwork. ### Who it's for Homeowners with weak hot water pressure upstairs, anyone converting from a combi to a system boiler, families adding a second bathroom, and properties replacing a 25-year-old vented cylinder. ### When you need it Survey within the week. Full cylinder swap is typically a one-day job; combi-to-system conversion is 2–3 days. ### Why it matters An unvented cylinder is a pressurised vessel under serious mains pressure, it must be installed by a G3-qualified engineer and certified, or building control and your home insurance won't recognise it. The cost of doing nothing ## What goes wrong when this is ignored. Most cylinder failures we replace are caused by a missed annual service, specifically a knackered expansion vessel that's been hammering the cylinder wall for years. ### Risks of waiting - Discharge from the tundish that nobody noticed for months, failed expansion vessel quietly destroying the cylinder - Undersized cylinder for the house, runs cold halfway through a family bath fill - Non-G3 install with no paperwork, insurance won't pay out on a leak claim ### Common mistakes - Buying the cheapest cylinder and skipping the magnetic filter / strainer on the cold feed - Ignoring the 12-month G3 service, vessel charge and PRV both need testing annually - Combi-to-system 'conversions' that leave the old cold tank in the loft for no reason Our process ## How the job actually runs. Same system every time. No improvising on your floor. - 01 ### Demand survey We count bathrooms, basins, simultaneous draws and household size. Cylinder size is matched to demand, not to whatever fits. - 02 ### Fixed quote Cylinder, all controls, pipework, discharge route and commissioning, in writing. - 03 ### Install & test Old unit drained and removed, new cylinder fitted, expansion vessel charged, PRV tested, tundish run to safe discharge. - 04 ### G3 certificate + handover Benchmark book filled in, G3 certificate issued, cylinder registered for warranty, controls demoed. What you get ## The outcomes that matter. ### Mains pressure to every tap Strong, even hot water, no more 'pencil-thin' shower upstairs while the kitchen tap runs. ### Multiple draws at once Two showers and a kitchen tap simultaneously, sized properly, the cylinder copes. ### Frees up the loft Combi-to-system or vented-to-unvented removes the cold tank and F&E tank from the loft, clean, dry, usable space. ### Solar/heat-pump ready We size and configure for future solar thermal or heat pump tie-ins where you're planning ahead. ### Long warranties Up to 25 years on the cylinder body (Megaflo, Telford Tempest) with annual service. ### Insurance-grade paperwork G3 certificate + Benchmark + warranty registration done on the day, not 'we'll email it later'. In depth ## Everything worth knowing before you book. The details a salesperson skips. Skim it, or read every word, both are useful. Questions on this? Talk to a Gas Safe engineer direct. 07455 748635 07702 523464 ### Vented vs unvented, which is right for you? Vented (open-vent) cylinders rely on a cold water tank in the loft for pressure. Cheap and simple, but pressure upstairs is always weak. Unvented cylinders run directly off the mains, pressure is the same at every tap on every floor. Unvented is the right answer for nearly every modern home with reasonable incoming mains pressure (2+ bar). Where mains is poor, we'll quote a thermal store or a mains booster pump as the honest alternative. ### Sizing, the number that actually matters Under-sizing is the single most common cylinder mistake. Rule of thumb: 1 bath = ~100L of hot, 1 shower = ~50L, two-bath house = 200–250L minimum, three-bath family = 250–300L. We size for peak simultaneous draw, not for 'one tap at a time'. Going one size up costs ~£150 in cylinder cost and saves a decade of cold-shower complaints. ### Why unvented MUST be G3 Unvented cylinders are pressurised vessels. Building Regulations Part G3 makes it illegal to install one without a G3 qualification, and home insurers void claims on unrecorded installs. We're G3 certified, every install is registered with the local authority where required, and you get the certificate in your hand on the day. ### Annual servicing of unvented cylinders G3 servicing is a separate annual check from your boiler service. It covers expansion vessel charge pressure test, PRV (pressure relief valve) test, T&P (temperature & pressure) valve test, immersion check, anode inspection on older units, and a flow/temperature performance test. Most cylinder failures are preventable with this annual check. Available standalone or bundled with your boiler service contract. ### Brands we install Heatrae Sadia Megaflo (industry standard, widest range, 25-year warranty), Telford Tempest (best stainless build, strong on bespoke sizes), Gledhill Stainlesslite (good value, solid 25-year). We don't fit budget no-brand cylinders, the saving is real on day one and gone within 5 years. General work gallery ## Recent Heatrite jobs that show the standard of our work. A broader look at recent installs, hot water systems, testing work and finished jobs across domestic and commercial sites. Commercial heating Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Oil heating Installed and commissioned by Heatrite. Unvented cylinders Installed and commissioned by Heatrite. Hot water systems Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Gas testing Installed and commissioned by Heatrite. Bathroom installation Installed and commissioned by Heatrite. Unvented cylinders Installed and commissioned by Heatrite. Bathroom installation Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Hot water systems Installed and commissioned by Heatrite. Hot water systems Installed and commissioned by Heatrite. Oil heating Installed and commissioned by Heatrite. Unvented cylinders Installed and commissioned by Heatrite. Boiler installation Installed and commissioned by Heatrite. Unvented cylinders Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Hot water systems Installed and commissioned by Heatrite. Commercial heating Installed and commissioned by Heatrite. Previous slideNext slide Frequently asked ## Straight answers, no fluff. Can't see your question? Call 07455 748635 or 07702 523464. Can I convert from a combi to a system boiler with a cylinder?Yes, and it's often the right answer for 3+ bathroom homes. We'll quote the whole job: new system boiler, sized unvented cylinder, all controls, removal of the redundant combi and a tidy install. Typically 2–3 days on site. How long does an unvented cylinder swap take? What about the discharge pipe (tundish)? Do you do landlord cylinders / HMOs? Will my existing radiators work with the new system? What if my mains pressure is poor? Payment & finance ## Card, Klarna or Clearpay, pay the way that suits you. Boilers, bathrooms and larger installs can be spread over time with Klarna or Clearpay finance, just ask when you book. - ### Card payments on site We carry a card machine in the van, tap, chip & PIN or contactless on completion. ### Klarna Spread the cost of your boiler or bathroom install with flexible Klarna finance options. ### Clearpay Pay over time with Clearpay, ideal for boilers, cylinders and full bathroom fits. Ready when you are ## Book your vented & unvented job today. Written fixed quote. Gas Safe engineer. No upsell, no pressure. Get my cylinder quote 07455 748635 07702 523464 Gas Safe registered 24/7 cover 5-star rated locally Related services ## Other things we look after. ← Back to homepage ### Boilers Learn more ### Power Flushing Learn more ### Bathroom Installations Learn more ### Plumbing Learn more Gas Safe heating & plumbing specialists based in London Colney, St Albans, serving homes and commercial properties across Hertfordshire & the Home Counties. Mon–Sat 8:00–17:30, with 24/7 emergency response. ### Domestic Boiler Installation & Servicing - Plumbing - Emergency Call Outs - Bathrooms - Vented & Unvented Hot Water Systems - Heating & Hot Water Controls - LPG Heating & Boilers ### Commercial - Plant Room Installation & Purging - Tightness Testing & Purging - Power Flushing - Commercial Plumbing - Commercial Heating & Gas - 24/7 Call Out - Unvented Hot Water Systems - Warm Air Heaters - Maintenance Contracts ### Company - About - Service Areas - Our Work - Reviews - Contact ### Contact - 07455 748635 - 07702 523464 - 07584 076105 - info@heatrite.uk - 17 Manor Rd, London ColneySt Albans AL2 1PN © 2026 Heatrite Plumbing & Heating Ltd. All rights reserved. Privacy PolicyCookie PolicyTerms & Conditions·Company No. 15149175 · Gas Safe Call nowRequest Estimate