The Role of Leakage Inspection and Hydro Testing in Safe CNG Operation

Why Leak Inspection Matters

A CNG system stores gas at high pressure and carries it through a network of pipes, valves and joints to the engine. Over time, vibration, heat and everyday wear can loosen fittings or age seals. Most of these issues are easy to fix when caught early, which is why leak inspection is one of the most important parts of owning a CNG vehicle.

A well-maintained, professionally fitted system is designed to operate safely. Regular inspection simply makes sure it stays that way.

What a Leak Check Involves

During a leak inspection, a technician checks the parts of the system where gas could escape — typically the cylinder valve, high-pressure pipes, joints, the reducer and connections in the engine bay. Checks are usually carried out using leak-detection solutions or suitable gas-detection equipment, followed by a pressure check to confirm the system is holding gas as expected.

Any loose fittings, worn seals or damaged pipes found during the check should be tightened or replaced with genuine components before the vehicle goes back on CNG.

Warning Signs You Should Never Ignore

If you notice any of the signs below, stop using CNG, switch to petrol if it is safe to do so, and bring the vehicle to a workshop for inspection as soon as possible. Do not try to locate or fix a gas leak yourself, and avoid smoking or using any open flame near the vehicle.

• A smell of gas inside the cabin, in the boot or around the engine bay
• A hissing sound near the cylinder, pipes or reducer
• The CNG level dropping noticeably faster than usual, or falling while the car is parked
• Difficulty starting or running on CNG that appears suddenly

What Is Cylinder Hydro Testing?

Hydro testing (hydrostatic testing) is a periodic check of the CNG cylinder itself. In general terms, the cylinder is removed from the vehicle, filled with water and pressurised beyond its normal working pressure under controlled conditions to confirm it can still safely hold gas. It is also inspected for corrosion, dents or other damage.

Hydro testing is carried out at authorised testing facilities, and a cylinder that passes is marked or certified accordingly. A cylinder that fails should be taken out of service and replaced rather than reused.

Why Periodic Re-Testing Matters

Like any pressure vessel, a CNG cylinder is subject to wear over its life. Periodic re-testing helps confirm the cylinder remains fit for use and is generally required to keep your CNG system compliant. The applicable re-testing interval depends on the cylinder type and current regulations, so please check your cylinder's test date and confirm the requirement with our team or your local RTO.

Combining routine leak checks at every service with hydro testing when it falls due is the simplest way to keep your CNG vehicle safe. Our team can inspect your system, check your cylinder's test status and help arrange testing when it is due.