Why hydro testing is compulsory
A CNG cylinder stores gas at around 200 bar — roughly 100 times the pressure in your tyres. Over years of filling, heat, road vibration and moisture, the steel can corrode or weaken without any visible sign. A hydrostatic test proves the cylinder can still safely hold that pressure.
Under the Gas Cylinders Rules, 2016, every on-board CNG cylinder must be retested every 3 years at an approved testing station. A cylinder that passes is stamped with the new test date and you receive a certificate. Fuel stations are told not to fill cylinders whose test has expired, and it can also become an issue during insurance claims and RTO checks.
What's included
- Safe de-gassing, removal and refitting of the cylinder
- Valve removal and inspection of threads
- Internal and external visual inspection
- Hydrostatic stretch test at 300 bar in a water jacket
- Drying, valve refit at correct torque and leak test
- Stamping of the test date and a test certificate
- WhatsApp reminder before your next due date
Step by step
- Check-in — we record your vehicle number, RC and cylinder serial number, manufacture date and last test date.
- De-gassing & removal — remaining CNG is vented safely and the cylinder is unbolted from the vehicle.
- Valve removal — the cylinder valve is removed and inspected; damaged valves are flagged for replacement.
- Visual inspection — inside and out, for dents, cuts, corrosion, bulges and thread damage.
- Hydrostatic test — filled with water, placed in a water jacket and pressurised to 300 bar (1.5× working pressure). Total and permanent expansion are measured.
- Pass / fail decision — if permanent expansion is within the limit, it passes. If not, the cylinder is condemned and made unusable, as the rules require.
- Drying & refit — the cylinder is dried internally, the valve refitted and leak tested, and the cylinder remounted on your vehicle.
- Stamping & certificate — new test date stamped; certificate handed over and shared on WhatsApp.
How long is a test valid?
A hydro test is valid for 3 years. The first test is due 3 years from the cylinder's manufacture date, and every 3 years after that.
| Situation | What to do |
|---|---|
| Last test less than 33 months ago | You're fine — set a reminder |
| Due within 3 months | Book now to get a convenient slot |
| Test date has passed | Stop refilling and test as soon as possible |
| Cylinder in an accident, fire or flood | Test immediately, regardless of date |
| Bought a used CNG vehicle | Check the stamp before your first refill |
Testing charges
| Cylinder size (water capacity) | Typical vehicle | Price per cylinder |
|---|---|---|
| 10 L | Small / special use | ₹1,100 |
| 20 L | Auto rickshaws | ₹1,300 |
| 30 L | Hatchbacks | ₹1,500 |
| 60 L | Sedans, SUVs, taxis | ₹1,900 |
| Cascade cylinder | Stations & industry | ₹1,700 |
Fleet discount of 5–15% applies automatically for 5 or more cylinders. Valve replacement, if needed, is charged separately and only with your approval.
Safety standards we follow
- Testing as per the Gas Cylinders Rules, 2016 under PESO
- Cylinders built to IS 15490 (on-board CNG cylinders) tested to its requirements
- Calibrated pressure gauges and water-jacket equipment, checked on schedule
- Water-based testing — no gas is used during the pressure test
- Failed cylinders are condemned so they can never return to a road
- Trained technicians with PPE and a defined de-gassing area
Before you book
Yes — most CNG vehicles run on petrol too, but we recommend waiting at the centre. The test takes 2–3 hours and the cylinder is refitted to your vehicle on the spot.
The rules require a failed cylinder to be condemned so it can't be reused. We'll explain the result, show you the reading and quote for a new certified cylinder with fitment. You won't be charged for anything you didn't approve.
No. Arrive with whatever gas is left — our team vents it safely. Running low on CNG before the visit simply means less gas is released.
Yes. Every cylinder that passes gets the new test date stamped on it and a test certificate. We also share a copy on WhatsApp so you don't lose it.
Retest due this month?
Same-day slots open until an hour before start time. Book now and skip the queue.