How often an F-gas system needs a leak check depends on the carbon-dioxide equivalent of its charge, not on a single kilogram number that fits every refrigerant. A modest weight of a high-impact gas can sit in a stricter band than a heavier charge of a lower-impact gas. Published rules group equipment into bands: smaller charges may have no routine check or a long interval, and larger carbon-dioxide-equivalent charges are checked more often. A fixed leak-detection system can lengthen the interval where the rules allow it. Read the current GOV.UK page for the system in front of you before you write a date in the log.
Tonnes of carbon-dioxide equivalent
The duty is written in tonnes of carbon-dioxide equivalent. That figure combines how much gas is in the system with how strongly that gas warms the atmosphere relative to carbon dioxide. Two cassettes with the same kilogram charge can therefore fall either side of a threshold if the refrigerants differ. Copying a kilogram rule from an old label is how operators miss a check, or pay for one they do not owe. There is no one kilogram threshold for every UK system. Leak-check thresholds depend on the gas as well as the weight of the charge. Check the current GOV.UK guidance for your equipment. GOV.UK's certification guidance explains who may work on the equipment.
A ladder of intervals, without a printed cut-off
Think of a ladder. Below the first rung, many smaller systems have no routine leak-check duty, subject to the sealed-equipment rules. Above it, checks are periodic. Further up the ladder the gap between checks shortens. The top of the ladder is the shortest interval. This page deliberately does not print a kilogram cut-off, because that cut-off would be wrong for some gases and may move when the guidance moves. Larger equivalent charges mean more frequent checks. The operator keeps the record: date, result, and who did the check. The person who carries out the check has to be certified for that work. A caretaker with a bottle of soapy water is not the compliance method.
Handover figures before a date goes in the diary
This page will not tell you how to leak-test a circuit, which instrument to buy, or how to handle refrigerant. Those are procedures for certified people. If a check finds a leak, the repair and any recovery belong to them as well. Venting is illegal. Domestic single splits are often, but not always, below the point where routine checks apply. A VRF plant on a shop roof often is not. The only honest step is to use the charge and the gas from the label or the commissioning sheet and compare them with the current GOV.UK guidance, or to ask your certified contractor to do that comparison in writing. Ask the installer, at handover, for the refrigerant type, the charge, the carbon-dioxide equivalent if they will calculate it, and a plain statement of whether routine leak checks apply and how often under the guidance then in force. File it with the log. Revisit that statement if you add indoor units, change refrigerant, or inherit a system with no paperwork. A larger charge can step you up a band. The inspections page for air conditioning is a different duty, triggered by cooling output, and you can owe both. Energy Saving Trust's air-to-air pages describe smaller heat-pump splits. They do not set the leak-check interval.
Frequently asked questions
Is there one kilogram threshold for every UK system?
No. Leak-check thresholds are set in tonnes of carbon-dioxide equivalent and depend on the gas as well as the weight of the charge. Check the current GOV.UK guidance for your equipment.
Does a leak-detection system mean I never need a manual check?
No. Where the rules allow, a fixed leak-detection system can lengthen the interval. It does not erase the duty. Confirm the interval on the current GOV.UK page and keep the detector itself maintained.
Who has to arrange the check?
The F-gas operator, meaning the person or organisation with actual control of the equipment, arranges it and keeps the record. The check itself is done by someone with the right certification.
Are hermetically sealed units outside routine checks?
Hermetically sealed equipment that is labelled as such can sit outside routine checks below a smaller threshold. The wording of that exemption is on the current GOV.UK guidance. Do not assume a shop system qualifies because it looks neat.
Is an air conditioning inspection the same diary entry?
No. GOV.UK's air conditioning inspections page is a different duty, triggered by cooling output. Leak checks follow carbon-dioxide equivalent. You can owe both.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.