AC gas refill: how often is normal, and why every year means a leak

A split or window AC does not consume refrigerant. The gas goes round and round in a sealed copper circuit and, if nothing is wrong, the charge that went in at the factory is the charge that is still there ten years later. So the honest answer to "how often should I refill the gas" is: you should not have to. If you are paying for a top-up every March, you are paying for the same gas to escape through the same hole, and the hole is the thing that needs fixing.

That said, small losses do happen over years, especially at joints, and a unit that has genuinely lost some charge will cool weakly. A refill on a split unit is ₹700 on our rate card. The point of this guide is to help you pay for it once, not annually.

How you know the gas is actually low

Low refrigerant has a particular pattern. It does not stop the AC overnight; cooling fades over weeks. The compressor runs for long stretches without reaching the set temperature. The thin copper pipe at the outdoor unit, and sometimes the indoor coil, frosts or ices up. You may hear a faint hiss or bubbling at the indoor unit.

The catch is that poor airflow produces almost the same picture. Dirty filters and a clogged indoor coil also make the coil freeze and the room stay warm. So before anyone talks about gas, the filters should be clean and the coil should have been looked at. A technician who arrives, puts gauges on the unit and tops it up without asking about the filters or checking for a leak is not solving your problem.

Why "yearly refill" is a red flag

If the unit needed gas last year and needs it again this year, the refrigerant is going somewhere. Common escape points:

• Flare nuts where the copper pipes join the indoor and outdoor units. A nut that was slightly under- or over-tightened at installation weeps for years.
• Brazed joints on the coil or the pipe runs, which crack with vibration.
• Corroded copper or aluminium on the coil. Near the coast — Muthukur, Krishnapatnam, the eastern side of Nellore — salt air eats the fins and eventually the tubes. Pinholes follow.
• Rubbing pipes where the line set touches a bracket or wall and has worn through the insulation and then the copper.
• Service valves whose cores or caps were left loose after the last visit.

A top-up without a leak repair buys you a few months. The gas leaks out again, the compressor runs low on charge and hot, and the oil that travels with the refrigerant runs low too. Repeated low-charge running is one of the ways a compressor ages early, and the compressor is the expensive part.

What a proper refill visit looks like

A refill done right has more steps than "connect cylinder, open valve":

1. Confirm the charge is low with gauges, and rule out airflow problems.
2. Find the leak. Soap solution on the joints, or a pressure test with nitrogen on a unit that has lost most of its gas. On a bad corrosion case, an electronic leak detector.
3. Fix the leak — re-flare a joint, re-braze, or replace a section of pipe. If a coil is corroded through, that is a part, shown at MRP before fitting.
4. Vacuum the system with a pump to pull out air and moisture. Skipping this step is common and it is why some refills "do not hold".
5. Charge by weight to the figure on the outdoor unit's nameplate, using the gas printed there — R-32 and R-22 are not interchangeable and should never be mixed.
6. Run and check pressures and the temperature drop at the indoor unit.

If your last refill took ten minutes, at least two of those steps were skipped.

R-32, R-22 and what it means for you

Older units, mostly pre-2015, run on R-22. Newer ones run on R-32, and some on R-410A. The gas type is printed on the sticker on the side of the outdoor unit. Check it before the visit so the technician brings the right cylinder; our ₹700 rate covers split units on R-32 or R-22. Never let anyone top up an R-22 unit with "whatever is in the van". Mixing gases ruins the charge and can damage the compressor.

When a refill is not worth it

If the leak is in the indoor or outdoor coil of a unit that is more than ten or twelve years old, the coil replacement plus the gas can approach the cost of a basic new unit, and the old compressor is still old. That is the moment to stop and weigh repair against replacement; we have a separate guide on exactly that decision. A leak at a flare nut or a pipe joint, on the other hand, is a cheap fix on a unit of any age.

Keeping the gas where it belongs

• Insist on the leak check before any refill, and ask what was found.
• Have the flare joints inspected at each service; they are the usual weak point.
• On the coastal side, have the outdoor coil washed at every service and ask for corrosion-resistant coils when you buy.
• Keep the line set clear of anything that rubs or pulls on it.
• Note the date and amount of any refill. If it happens twice, insist on the leak being found.