--- title: "Gas Tightness Testing & Purging in Hertfordshire | Heatrite" description: "Certified IGEM/UP/1 tightness testing and purging for domestic and commercial gas installations across Hertfordshire, Buckinghamshire, Berkshire, Surrey and London. Let-by checks, strength tests and signed certificates." lang: en-GB json-ld: | [ { "@context": "https://schema.org", "@type": "Organization", "@id": "https://heatriteplumbingandheating.co.uk/#organization", "name": "Heatrite Plumbing & Heating", "url": "https://heatriteplumbingandheating.co.uk/", "logo": "/__l5e/assets-v1/316b6485-0482-4b28-9d61-8fa7c9b03ca2/heatrite-favicon.png", "telephone": "+44 7455 748635", "email": "info@heatrite.uk", "address": { "@type": "PostalAddress", "streetAddress": "17 Manor Rd, London Colney", "addressLocality": "St Albans", "postalCode": "AL2 1PN", "addressCountry": "GB" }, "sameAs": [ "https://www.facebook.com/profile.php?id=61551391771285", "https://www.instagram.com/heatriteplumbingandheating/" ] }, { "@context": "https://schema.org", "@type": "WebSite", "@id": "https://heatriteplumbingandheating.co.uk/#website", "name": "Heatrite Plumbing & Heating", "url": "https://heatriteplumbingandheating.co.uk/", "inLanguage": "en-GB", "publisher": { "@id": "https://heatriteplumbingandheating.co.uk/#organization" }, "potentialAction": { "@type": "SearchAction", "target": "https://heatriteplumbingandheating.co.uk/?q={search_term_string}", "query-input": "required name=search_term_string" } }, { "@context": "https://schema.org", "@type": "Service", "serviceType": "Gas Tightness Testing", "name": "Tightness Testing & Purging", "areaServed": { "@type": "City", "name": "Hertfordshire" }, "provider": { "@type": "LocalBusiness", "name": "Heatrite Plumbing & Heating", "telephone": "07455 748635", "address": { "@type": "PostalAddress", "streetAddress": "17 Manor Rd, London Colney", "addressLocality": "St Albans", "postalCode": "AL2 1PN", "addressCountry": "GB" } }, "description": "Certified IGEM/UP/1 tightness testing and purging for domestic and commercial gas installations across Hertfordshire, Buckinghamshire, Berkshire, Surrey and London. Let-by checks, strength tests and signed certificates." }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "How long does a tightness test take?", "acceptedAnswer": { "@type": "Answer", "text": "A standard domestic test takes about 30–45 minutes including the let-by check, stabilisation and test duration. Commercial medium-pressure tests run 60–90 minutes depending on pipe volume." } }, { "@type": "Question", "name": "Do I get a certificate?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, signed, dated, with photographed gauge readings, handed over on the day and emailed within 24 hours. We keep a copy on file for 7 years for re-issue." } }, { "@type": "Question", "name": "Can you test after a leak repair?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, that's a common booking. After any leak repair or pipework alteration, a fresh tightness test is the only way to prove the install is safe to use." } }, { "@type": "Question", "name": "Do you test commercial as well as domestic?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, full commercial Gas Safe registration covers domestic single-meter installs through to medium-pressure commercial pipework runs." } }, { "@type": "Question", "name": "What if the test fails?", "acceptedAnswer": { "@type": "Answer", "text": "We'll diagnose the leak source on the same visit where possible, quote the repair, and re-test once repaired. No charge for the re-test if we did the original repair." } }, { "@type": "Question", "name": "Do you provide standalone purging?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, purging-only visits are available after appliance swaps or pipework alterations, with calculated volumes and oxygen verification on the certificate." } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://heatriteplumbingandheating.co.uk/" }, { "@type": "ListItem", "position": 2, "name": "Services", "item": "https://heatriteplumbingandheating.co.uk/services" }, { "@type": "ListItem", "position": 3, "name": "Tightness Testing & Purging", "item": "https://heatriteplumbingandheating.co.uk/services/tightness-testing" } ] } ] --- St Albans Mon–Sat 8:00–17:30 · 24/7 Emergency · Gas Safe Registered [info@heatrite.uk](mailto:info@heatrite.uk)[07455 748635](tel:+447455748635)[07702 523464](tel:+447702523464)[07584 076105](tel:+447584076105) [![Heatrite Plumbing & Heating](/__l5e/assets-v1/6766d4f9-4594-4088-8ae7-80c8fa1d440c/heatrite-logo.png)](/) [About](/about) [Domestic](/services) [Commercial](/services) [Service Areas](/service-areas) [Our Work](/our-work)[Contact](/contact) [07455 748635](tel:+447455748635) [Request Estimate](/contact) Tightness Testing · IGEM/UP/1 · Hertfordshire # Gas Tightness Testing & Certified Purging Independent IGEM/UP/1 and UP/1B tightness testing, let-by checks, strength tests and certified purging of new or modified gas installations, with a signed, photographed certificate handed over on the day. [Book tightness test](/contact) [07455 748635](tel:+447455748635)[07702 523464](tel:+447702523464) IGEM/UP/1 & UP/1B · Domestic and commercial · Certificate on the day - IGEM/UP/1 & UP/1B qualified - Calibrated digital manometers - Photographed gauge readings - Records kept for 7 years - Commercial Gas Safe registered Service overview ## What tightness testing & purging 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 Pressure tightness testing and certified purging of gas installations, from a single domestic meter installation through to large commercial pipework runs at medium pressure. Includes let-by, tightness and (where applicable) strength tests, with documented purge volumes and a signed certificate. ### Who it's for Landlords needing pre-let evidence of a safe gas install, builders/developers signing off new gas pipework, facilities managers commissioning a new commercial install, and any property owner who's had recent gas pipework modifications. ### When you need it Immediately after any new or altered gas pipework, before reconnecting a meter, before commissioning new appliances, after a suspected leak, after a building refurbishment, or when an existing certificate has been lost or never issued. ### Why it matters A tightness test is the only way to prove a gas installation is safe and the only document an insurer or new occupier will trust. A correctly executed test catches let-by, micro-leaks and faulty isolation valves before they become incidents, and a certified purge ensures no air or oxygen mix remains in the supply. The cost of doing nothing ## What goes wrong when this is ignored. Untested gas pipework is a liability that rarely surfaces until it's too late, and the gap between 'looks fine' and 'safely commissioned' is exactly what the IGEM procedure is designed to catch. ### Risks of waiting - Undetected let-by on an emergency control valve means the meter never properly isolates, every disconnection becomes a hazard. - Hairline pipework leaks lose pressure slowly enough to pass a casual visual check but show clearly on a calibrated tightness test. - Skipping a certified purge after pipework changes can leave air pockets that destabilise burner ignition and cause repeat lockouts. - No paperwork = no insurance claim, every loss adjuster asks for the most recent tightness certificate first. ### Common mistakes - Relying on a soap-and-bubble check instead of a calibrated manometer reading over the correct test duration. - Skipping the let-by test, which catches faulty ECVs that would otherwise leak through a 'closed' valve. - Forgetting to record stabilisation time and temperature, which makes the test results unprovable later. - Purging by 'feel' rather than calculating volumes against the actual pipe internal volume. Our process ## How the job actually runs. Same system every time. No improvising on your floor. 1. 01 ### Identify the installation We confirm the pipework run, meter type, operating pressure (LP/MP), all appliances on the supply and any branches that need isolating during the test. 2. 02 ### Let-by test Emergency control valve closed and held against system pressure to prove it isolates fully. Any leak through the valve is recorded and addressed before continuing. 3. 03 ### Stabilisation & tightness test System pressurised to the IGEM-specified test pressure, stabilisation period observed (5+ minutes on most installs), pressure held for the required test duration with readings logged. 4. 04 ### Strength test (where required) On medium-pressure or new commercial pipework, a strength test at 1.5× max operating pressure is run before the tightness phase, with results recorded. 5. 05 ### Certified purge & certificate Purge volumes calculated against pipe internal volume, oxygen levels verified clear, signed certificate issued on the day with photographed gauge readings. What you get ## The outcomes that matter. ### Certificate on the day Signed, dated, photographed gauge readings, in your inbox before we leave site. No 'we'll email it later'. ### Insurance-grade evidence Every test follows IGEM/UP/1 or UP/1B and includes the documentation an insurer or loss adjuster will ask for. ### Faults found before failure Let-by, micro-leaks and faulty ECVs caught and addressed before they cause an incident. ### Domestic and commercial Same engineer covers single-meter domestic installs through to medium-pressure commercial pipework runs. ### Records kept for 7 years We store every test result and certificate so we can re-issue copies for landlord re-lets, refinancing or insurance renewals. ### Fixed price, no surprises Quoted per test on the survey, no add-ons on the invoice. 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](tel:+447455748635) [07702 523464](tel:+447702523464) ### What IGEM/UP/1 actually requires IGEM/UP/1 is the industry procedure for low-pressure tightness testing of pipework up to 25mm. It defines the test pressure, the stabilisation period, the test duration, the maximum allowable pressure drop, and the calibration requirements for the manometer. A test that skips any of those isn't an IGEM/UP/1 test, it's a guess. UP/1B covers medium-pressure (75 mbar–2 bar) installations and adds a mandatory strength test. ### Let-by, the bit most people miss Before any tightness test, the emergency control valve must be proven to isolate fully. The valve is closed against pressure and held for the let-by period, any pressure rise downstream means the valve isn't seating and must be repaired or replaced before testing continues. A skipped let-by check is the single most common reason a 'passed' tightness test isn't actually valid. ### Purging, calculating not guessing After a new install, pipework alteration or supply reconnection, residual air must be purged. The correct purge volume is calculated against pipe internal volume (litres per metre of pipe ID), with a safety multiplier per IGEM/UP/1. We measure the oxygen content at the end of the purge to confirm the line is gas-clean, and record both the calculated volume and the verified O₂ reading on the certificate. ### When you need a fresh test Any time gas pipework is altered or extended, after a meter swap, after a new appliance install, when a property changes hands and no recent certificate exists, when a landlord re-lets a property, or when an insurer requests current evidence. Old certificates aren't grandfathered against new pipework. ### Commercial medium-pressure work Medium-pressure commercial pipework (75 mbar–2 bar) needs UP/1B testing, with a strength test at 1.5× MOP before the tightness phase, longer stabilisation periods, and tighter allowable drops. We do both on the same visit where the install includes a regulator step-down. 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 boiler internals during installation with exposed heat exchanger and neatly routed pipework](/__l5e/assets-v1/e9a65e47-b343-4aa3-933f-015200070c72/work-4.png) Commercial heating Installed and commissioned by Heatrite. ![Twin commercial boiler setup with both front panels removed for servicing and commissioning](/__l5e/assets-v1/38666ee2-c4d1-4fbb-a25e-ce786403957a/work-5.png) Commercial heating Installed and commissioned by Heatrite. ![Wall-mounted Vaillant boiler installation with insulated pipework and copper connections](/__l5e/assets-v1/456ba7b5-5c1c-4b00-b43e-404591d5ed03/work-6.png) Boiler installation Installed and commissioned by Heatrite. ![External oil tank installation positioned neatly between brick walls](/__l5e/assets-v1/4de611ea-cafe-4c20-86d6-42cd9aa3c1d4/work-7.png) Oil heating Installed and commissioned by Heatrite. ![Baxi unvented hot water cylinder fitted in a compact airing cupboard with copper pipework](/__l5e/assets-v1/a0cb8061-dd27-4f69-b39e-1aad4c311c0a/work-8.png) Unvented cylinders Installed and commissioned by Heatrite. ![Multiple Stelrad hot water cylinders installed with expansion vessels and tidy copper distribution pipework](/__l5e/assets-v1/dbe03410-435b-401c-8d93-526e266960c5/work-9.png) Hot water systems Installed and commissioned by Heatrite. ![Outdoor Vaillant boiler cabinet installation with exposed copper pipework and balanced flue](/__l5e/assets-v1/a10b18c8-f27f-4f0a-9a8a-b248c5575dbd/work-10.png) Boiler installation Installed and commissioned by Heatrite. ![Commercial gas purge and flame testing setup outside a brick building](/__l5e/assets-v1/ed3a08a3-1f93-4247-950b-4507cae5d7ba/work-11.png) Gas testing Installed and commissioned by Heatrite. ![Finished cloakroom installation with herringbone wall tiles and wall-hung toilet](/__l5e/assets-v1/f5382f0a-f6f6-42a0-8ba6-3eb4e0e9eba4/work-12.png) Bathroom installation Installed and commissioned by Heatrite. ![Unvented hot water cylinder installation with neat copper pipework routed in a compact cupboard](/__l5e/assets-v1/5966169f-df43-4e6a-8fa4-00d5ada11b89/work-13.png) Unvented cylinders Installed and commissioned by Heatrite. ![Freestanding bath installation with illuminated wall niches in a finished bathroom](/__l5e/assets-v1/7557adb8-2be1-4859-8ce8-0547c095a975/work-14.png) Bathroom installation Installed and commissioned by Heatrite. ![New Vaillant boiler installation with exposed copper pipework and clean wall finish](/__l5e/assets-v1/17bc8561-367c-453d-9309-b51b22eceeba/work-15.png) Boiler installation Installed and commissioned by Heatrite. ![Commercial plant room with multiple large heating units and insulated pipework](/__l5e/assets-v1/22d33404-7c84-47d9-addc-12e0414b4ced/work-16.png) Commercial heating Installed and commissioned by Heatrite. ![Vaillant boiler installation in a service cupboard with diagnostic equipment attached](/__l5e/assets-v1/8ac0bcb5-ca6c-4391-a20e-46ac8c7b7e77/work-17.png) Boiler installation Installed and commissioned by Heatrite. ![Commercial heating installation with multiple wall-mounted units and copper distribution pipework](/__l5e/assets-v1/95c4e5ee-245f-47ab-b9b6-0280e97b475f/work-18.png) Commercial heating Installed and commissioned by Heatrite. ![Vaillant boiler fitted in a utility room with tidy vertical pipework connections](/__l5e/assets-v1/e2b0e0f3-7593-4c3b-87ef-e6be613fc4a9/work-19.png) Boiler installation Installed and commissioned by Heatrite. ![Hot water cylinder and underfloor heating manifold installation with twin circulating pumps](/__l5e/assets-v1/9a157181-7e9a-48de-a918-dbb3064b22e7/work-20.png) Hot water systems Installed and commissioned by Heatrite. ![Pressurised hot water cylinder installation with expansion vessels and control components](/__l5e/assets-v1/ba83dadf-8018-41e5-9bce-095350912213/work-21.png) Hot water systems Installed and commissioned by Heatrite. ![External heating unit installed neatly beside a brick wall with isolated service connections](/__l5e/assets-v1/56b5860d-136e-437a-bef1-70bbcf99ea4d/work-22.png) Oil heating Installed and commissioned by Heatrite. ![Tall unvented hot water cylinder installation fitted neatly into bespoke white cabinetry with copper pipework](/__l5e/assets-v1/9118dd23-8319-41e4-a6b7-f6a03823c75c/work-23.png) Unvented cylinders Installed and commissioned by Heatrite. ![Vaillant boiler fitted inside a tall cupboard with concealed services and tidy copper pipework](/__l5e/assets-v1/60230cd2-2c07-4803-a0a2-562033083e2c/work-24.png) Boiler installation Installed and commissioned by Heatrite. ![Stainless hot water cylinder installation in a storage room with neatly routed copper connections](/__l5e/assets-v1/ffa01736-335e-4410-a061-4e8e648d54a9/work-25.png) Unvented cylinders Installed and commissioned by Heatrite. ![Commercial cascade boiler installation with twin wall-mounted units and extensive plant room pipework](/__l5e/assets-v1/1f759664-50e1-4b96-a2ae-ea8b1e996c37/work-26.png) Commercial heating Installed and commissioned by Heatrite. ![Large commercial calorifier installation in a plant room with insulated pipework and control panel](/__l5e/assets-v1/1bfb9470-99ee-49ba-9b20-0afd0485b069/work-27.png) Commercial heating Installed and commissioned by Heatrite. ![Blue pressurised vessel positioned in a basement plant room during hot water system upgrade works](/__l5e/assets-v1/2c721001-b5ca-492e-ba58-f325618b5709/work-28.png) Hot water systems Installed and commissioned by Heatrite. ![Plant room expansion vessel and Vaillant boiler installation with insulated services and pressure gauge](/__l5e/assets-v1/cb4d1710-6f69-4b17-b976-4188487760c2/work-29.png) Commercial heating Installed and commissioned by Heatrite. Previous slide Next slide Frequently asked ## Straight answers, no fluff. Can't see your question? Call [07455 748635](tel:+447455748635) or [07702 523464](tel:+447702523464). How long does a tightness test take? A standard domestic test takes about 30–45 minutes including the let-by check, stabilisation and test duration. Commercial medium-pressure tests run 60–90 minutes depending on pipe volume. Do I get a certificate? Can you test after a leak repair? Do you test commercial as well as domestic? What if the test fails? Do you provide standalone purging? 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 tightness testing & job today. Written fixed quote. Gas Safe engineer. No upsell, no pressure. [Book tightness test](/contact) [07455 748635](tel:+447455748635) [07702 523464](tel:+447702523464) Gas Safe registered 24/7 cover 5-star rated locally Related services ## Other things we look after. [← Back to homepage](/) [ ![Gas Safe engineer installing a wall-mounted combi boiler](/assets/boilers-Dz3GzZ9b.jpg) ### Boilers Learn more ](/services/boilers)[ ![Engineer power flushing a central heating system](/assets/power-flushing-DGUFOFm0.jpg) ### Power Flushing Learn more ](/services/power-flushing)[ ![Modern bathroom installation with walk-in shower and brushed brass fittings](/assets/bathroom-installations-WIyfjKRg.jpg) ### Bathroom Installations Learn more ](/services/bathroom-installations)[ ![Plumber fitting a chrome kitchen tap with copper pipework](/assets/plumbing-DmY4tKrz.jpg) ### Plumbing Learn more ](/services/plumbing) ![Heatrite Plumbing & Heating](/__l5e/assets-v1/6766d4f9-4594-4088-8ae7-80c8fa1d440c/heatrite-logo.png) 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. 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