New Gas Tightness Test Rules from 1 October 2026: What Homeowners and Landlords Need to Know

Sep 23

4 min read

Conducting a tightness test procedure, using a digital pressure gauge to ensure the integrity of copper piping in a utility setup.

From 1 October 2026, all Gas Safe registered engineers in the UK must carry out gas

tightness tests under a new industry standard, IGEM/UP/1B Edition 4. If you own a home or rent out a property in South London, this change affects your gas safety checks, boiler installations and landlord gas safety certificates.

At Gasify we've already moved over to the new procedure. Here's a plain-English guide to what's changing and what it means for you.

What is a gas tightness test?

A gas tightness test checks that the gas pipework in your property has no leaks. Your engineer turns off the gas at the meter, connects a pressure gauge and watches for any drop in pressure over a set time. A drop can mean gas is escaping somewhere in the system.

Gas engineers carry out a tightness test:

During every landlord gas safety check (CP12)
Before and after boiler installations and replacements
After any work on gas pipework or appliances
When a gas leak is suspected

What's changing under IGEM/UP/1B Edition 4?

The Institution of Gas Engineers and Managers (IGEM) published Edition 4 in March 2026. Engineers had six months to switch over, and the old Edition 3 is withdrawn on 30 September 2026. These are the main changes:

1. Pass or fail now depends on the size of your whole gas system

Under the old rules, the pressure drop allowed was based mainly on the type of gas meter. The new standard uses the installation volume: the total amount of gas held in the meter, the pipework and the appliances. Your engineer now works out this volume before judging the result. A small flat and a large house with long pipe runs can therefore have different limits, which makes the test more accurate for each property.

2. Stricter checks on the pipework

This is the biggest change for customers. If the gauge moves at all during the test, even by an amount that's still within the permitted limit, the engineer must now isolate your appliances and test the pipework on its own. The pipework then has to show no noticeable pressure drop.

Small leaks in the pipework that might have passed before will now be picked up and have to be fixed. That's better for your safety.

3. Updated test steps

The procedure now includes set times for checking the emergency control valve (the lever next to your meter), for letting the pressure settle and for the test itself. There's also a clear rule for homes where the gas pressure is slightly low.

4. New purging calculation

After work on your gas supply, air has to be cleared from the pipes safely (this is called purging). The amount of gas needed is now worked out from your installation volume, so purging fits your property more closely.

What does this mean for you?

For homeowners:

A tightness test may take a few minutes longer than you're used to, especially if your engineer needs to isolate appliances.
If a very small leak is found in your pipework, it will need repairing before your system can be signed off as safe.
Your gas system won't be changed or upgraded just because the standard has changed. The update only changes how engineers test it.

For landlords:

Every landlord gas safety check after 1 October 2026 must include a tightness test done to the new standard. Make sure your engineer knows the new procedure.
Allow a little extra time on the day, and make sure your tenants know the engineer may need to reach each gas appliance.
Your current gas safety certificate stays valid until its renewal date. You don't need a new one because of this change.

Is your engineer up to date?

Only a Gas Safe registered engineer can legally work on gas appliances and pipework. Whoever you use, ask whether they're testing to IGEM/UP/1B Edition 4 from October 2026. A good engineer will be happy to explain.

At Gasify, we're fully up to date with the new standard. We carry out gas tightness tests, gas safety certificates and boiler services across South London, including Herne Hill, Brixton, Dulwich, Peckham, Camberwell, Forest Hill, Sydenham, Brockley and Nunhead.

Frequently asked questions

When do the new gas tightness test rules start?They become mandatory on 1 October 2026. Engineers could use either the old or new standard until 30 September 2026.

Will a gas safety certificate cost more?The test itself hasn't changed much in cost. It may take slightly longer, and if a leak is found, repairing it is a separate job.

Do I need to do anything to prepare?Just make sure your engineer can easily rea

ch the gas meter and all your gas appliances.

What should I do if I smell gas?Leave the property, don't use electrical switches, turn off the gas at the meter if it's safe to do so, and call the National Gas Emergency Service on 0800 111 999.