How to get your CNG cylinder hydro tested, and what it costs

Every CNG cylinder on an Indian vehicle has to be emptied, stripped of its valve and pressure tested once every three years, at a testing station approved by the Chief Controller of Explosives under PESO. Indian Oil-Adani Gas puts the charge for a passenger car cylinder at roughly ₹1,200 to ₹3,000, depending on the city and the station. The certificate you get back is what a CNG pump now wants to see before it fills your tank.

The rule, and who is checking

Rule 35(1) of the Gas Cylinders Rules, 2016 is blunt about it. No person shall fill any cylinder with compressed gas unless it has been examined and put through the hydrostatic or hydrostatic stretch test and the other tests in Schedule IV, within the period set by IS 15975 or as approved in writing by the Chief Controller. Sub-rule (2) says only testing stations approved by the Chief Controller may do that work. Rule 26 adds that a cylinder whose periodic retest is overdue shall not be charged until the retest is done. The Gas Cylinders (Amendment) Rules, 2025 took effect on 11 April 2025 and the three year interval for CNG, CBG and on-board hydrogen cylinders now sits in rule 35(1) itself.

Enforcement is the new part. On 23 September 2026 Indraprastha Gas said vehicles without a valid hydro test certificate are being denied refuelling across its network, and that an automated verification system is running at 10 stations. Cameras read the registration number, an AI application checks the cylinder's validity against PESO's online system, and alerts go out on handheld devices, LED displays and the public announcement system. IGL, which runs more than 1,000 CNG stations and serves about 2.1 million CNG vehicles, says it will extend the system to all its outlets.

What the test actually does

It is not a quick inspection. Indian Oil-Adani Gas lists the sequence: depressurise and degas the cylinder, open the valve and inspect inside, clean and dry it, take ultrasonic wall thickness readings, run the hydrostatic stretch test, clean and dry again, verify the tare weight, inspect inside and out, refit to the vehicle and issue the certificate. The stretch test fills the cylinder with water at high pressure and measures how much it expands and whether it returns to size. Corrosion, cracks and thinned walls are what the station is hunting for.

Remember the other clock. Rule 36 fixes the service life of an on-board CNG cylinder at twenty years. Past that, no test will save it and it has to come off.

Step by step for an owner

1. Find the due date. The last test date is stamped on the cylinder and printed on your certificate. Keep the certificate in the car and a photo of it on your phone.
2. Pick an approved station. PESO publishes a list of approved CNG cylinder testing stations on its site. IGL lists 16 PESO authorised centres with phone numbers and map coordinates across Delhi, Gautam Budh Nagar, Ghaziabad, Faridabad and Bahadurgarh. Outside the NCR, including Bengaluru, go by the PESO list or ask your city gas distributor.
3. Arrive with the tank close to empty. The gas has to be vented before anything else happens.
4. Get the certificate and make sure the details match your registration number.

IGL's own care sheet is worth following between tests. Run the car on petrol now and then so the petrol side stays healthy, insure the kit, never fit an LPG or other cylinder in place of the CNG one, do not weld or apply heat within 1.5 metres of a cylinder that has not been emptied, and do not park a vehicle with a fuel leak within 6 metres of any ignition source.

Sources

• Gas Cylinders Rules, 2016, full text
• IGL tightens checks on CNG cylinder hydro test certificates, Millennium Post
• All you need to know about CNG cylinder hydro testing, Indian Oil-Adani Gas
• PESO authorised hydro testing centres, IGL
• Steps to follow for CNG vehicle care, IGL
• Approved CNG cylinders testing station list, PESO
• Gas Cylinders (Amendment) Rules, 2025, Lexplosion