How to Fill a Paintball Tank (CO2 & HPA)

The first time I showed up to a paintball field with my own gear, I had no idea how tank fills worked. I walked up to the counter holding an empty HPA tank and just kind of stood there until someone took pity on me. Turns out it was dead simple — hand them your tank, they fill it, you go play. But there’s more to it than that, especially if you want to understand what’s actually happening, where else you can get fills, and how to keep your tank safe long-term.

This covers everything you need to know about filling both CO2 and HPA paintball tanks — where to go, what the process looks like, what it costs, and the safety stuff you shouldn’t skip.

CO2 vs. HPA: A Quick Recap

Before we get into fills, it helps to know which type of tank you have, because the fill process is completely different for each.

CO2 tanks are the smaller, usually all-metal cylinders. They’re measured in ounces — 9oz, 12oz, 16oz, and 20oz are the most common sizes. CO2 is stored as a liquid that converts to gas as it’s used. These are cheaper to buy and fill, but they’re less consistent in cold weather and not compatible with many modern markers.

HPA (High Pressure Air) tanks are the larger tanks with a regulator screwed onto the top. They’re measured by volume and pressure — something like “48/3000” means 48 cubic inches at 3,000 PSI, and “68/4500” means 68 cubic inches at 4,500 PSI. HPA gives you more consistent output pressure, works in any temperature, and is what most players use today.

If you’re not sure which is right for you, I break that down in my CO2 vs. HPA comparison. For this article, I’ll cover the fill process for both.

Where to Fill an HPA Tank

Paintball Fields

This is the easiest and most common option. Virtually every paintball field has an HPA fill station. Most charge a flat rate — usually around $5 — for unlimited fills throughout the day. Some include fills with your entry fee.

The fill stations at fields are purpose-built for paintball tanks. The staff knows what they’re doing, and the equipment has the right fittings and pressure regulation for paintball-specific tanks. If you’re already at a field to play, this is a no-brainer.

Dive Shops (Scuba Shops)

Scuba dive shops have high-pressure compressors for filling scuba tanks, and those same compressors can fill HPA paintball tanks. Not every dive shop will do it — some don’t want to deal with the liability or the small fill volume — but many will. Call ahead before showing up.

Expect to pay $3-7 per fill at a dive shop. They might look at you a little funny the first time, but most have dealt with paintball players before.

One thing to note: dive shops fill to specific pressures, and you need to tell them what your tank is rated for. A 3,000 PSI tank should be filled to 3,000 PSI, and a 4,500 PSI tank should be filled to 4,500 PSI. Don’t let them overfill, and don’t let them underfill either — you’re paying for a full tank.

Fire Stations

Some fire stations have cascade systems (banks of large compressed air cylinders) for filling SCBA tanks. Occasionally a friendly fire station will fill paintball tanks if you ask nicely. This is very hit-or-miss and definitely not something to rely on, but I’ve heard of players in rural areas making it work.

Personal Compressor (Home Fill)

If you play a lot and want the convenience of filling at home, you can buy a high-pressure compressor. I’ll cover this in more detail further down.

Where to Fill a CO2 Tank

CO2 is widely available because it’s used for a lot more than paintball — welding, beverage carbonation, aquariums, you name it. That means you have more options for fills.

Paintball Fields

Same as HPA — any paintball field will fill CO2 tanks. Usually $3-5 per fill.

Sporting Goods Stores

Dick’s Sporting Goods is the big one. Many locations have a CO2 fill station and will fill paintball tanks while you wait. Prices are typically in the $3-5 range. Bass Pro Shops and some Dunham’s locations offer fills too.

Call ahead to confirm they actually have CO2 in stock and that their fill station is working. Nothing worse than driving across town to find out their tank is empty.

Welding Supply Shops

Places like Airgas or local welding supply companies sell CO2 in bulk and can fill smaller paintball tanks. They’re used to filling 20lb and 50lb tanks for welding and industrial use, so your little 20oz paintball tank will be quick. Prices vary but are generally reasonable.

Some Walmart Locations

A handful of Walmart stores have CO2 fill capability, usually in the sporting goods department. This is inconsistent — many locations don’t offer it, and staff availability can be spotty. Don’t make it your primary plan, but if you happen to be near one that does it, it’s convenient.

Specialty Shops

Homebrew supply stores (for beer and soda making) and some aquarium shops deal with CO2 regularly and may fill paintball tanks. Again, call first.

How an HPA Fill Actually Works

If you’ve never had a tank filled before, here’s what to expect at a typical paintball field fill station.

Step 1: Hand Over Your Tank

Disconnect the tank from your marker first. Never try to fill a tank while it’s attached to your gun. Bring just the tank to the fill station.

The fill station operator will check your tank before filling it. They’re looking at two things: the hydro test date (more on that below) and whether the tank is in visually acceptable condition. If your tank is out of hydro or looks damaged, they won’t fill it.

Step 2: Connect to the Fill Station

The operator connects your tank to the fill station using a standard ASA (Air Source Adapter) fitting — the same thread that connects to your marker. They’ll snug it on by hand. Some stations have a whip (flexible hose), and some are direct-connect.

Step 3: Slow Fill

This is the part most people don’t know about. A good fill station operator fills the tank slowly. Here’s why: when you compress air rapidly, it generates heat. That heat causes the air molecules inside the tank to expand, which gives a false high-pressure reading on the gauge. If you fill fast to 4,500 PSI and then let the tank cool down, the actual pressure drops to maybe 4,000-4,200 PSI. You’re leaving shots on the table.

A slow fill — taking 30-60 seconds to reach full pressure — keeps the temperature down and gives you a more accurate, fuller fill. This is called a “cool fill.” If an operator just blasts your tank full in five seconds, the fill won’t be as complete.

At busy fields where there’s a line at the fill station, you might not always get a slow fill. That’s just the reality of high-volume game days. It’s not a big deal — you’ll still get a functional fill, it just might be slightly under rated pressure once it cools.

Step 4: Check and Disconnect

The operator checks the fill station gauge to confirm pressure, disconnects your tank, and hands it back. You’ll hear a small burst of air when they disconnect — that’s normal and expected, it’s just the air in the hose venting.

That’s it. The whole process takes about a minute.

How a CO2 Fill Works

CO2 fills are a different process because you’re dealing with a liquid, not compressed air.

Step 1: Weigh the Empty Tank

The operator weighs your empty tank first. Every CO2 tank has a tare weight stamped on it — this is the weight of the tank itself when empty. They need to know this to fill it to the correct weight.

Step 2: Connect to the Bulk Tank

Your tank gets connected to a much larger bulk CO2 cylinder using a fill adapter. The bulk tank sits upside down (or has a siphon tube) so that liquid CO2 flows into your tank.

Step 3: Fill by Weight

CO2 is filled by weight, not pressure. A 20oz tank gets filled with 20 ounces of liquid CO2. The operator monitors the scale and stops when the correct weight is reached.

Overfilling a CO2 tank is dangerous. As the liquid CO2 warms up, it expands. If there isn’t enough headspace in the tank for this expansion, the pressure can exceed safe limits. This is why filling by weight matters — it ensures there’s always room for the liquid to expand.

Step 4: Disconnect and Purge

The operator disconnects your tank. You’ll see a blast of CO2 vapor — that’s normal. Some operators will briefly open the tank’s pin valve to purge any air that got in during the connection process, which gives you cleaner CO2 and slightly better performance.

Tank Safety: The Stuff You Shouldn’t Skip

A paintball tank is a pressure vessel. HPA tanks operate at 3,000-4,500 PSI. That’s serious pressure, and while modern tanks are incredibly safe when maintained properly, there are a few things every tank owner should know.

Hydrostatic Testing

Every pressure vessel has a limited certified lifespan. Hydrostatic testing — “hydro” for short — involves filling the tank with water and pressurizing it beyond its normal operating pressure to make sure the tank material hasn’t weakened.

HPA tanks need hydro testing every 5 years. The test date is stamped on the tank, usually on the crown (top) of the cylinder. If you see something like “03-21” on your tank, that means it was last tested in March 2021 and is due for retesting by March 2026.

CO2 tanks follow DOT regulations and typically need retesting every 5 years as well, though some are certified for longer intervals depending on the material.

No reputable shop or field will fill a tank with an expired hydro date. Don’t even ask — they can lose their license for doing so. Getting a hydro test costs $25-40, and you can usually send your tank out through a local dive shop or paintball store. If your tank is nearing its expiration, factor in whether the hydro cost is worth it versus just buying a new tank, especially for older CO2 tanks that can be replaced for $25-30.

Burst Disks

Both CO2 and HPA tanks have burst disks — thin metal disks designed to rupture at a specific overpressure point before the tank itself fails. If your burst disk blows, you’ll know it — it’s loud, there’s a rush of gas, and your tank is now empty. It’s a safety feature doing its job.

If a burst disk blows, don’t try to DIY a fix. Take the tank to a paintball shop or pro shop to have it inspected and the burst disk replaced. They’re cheap but critical.

Visual Inspection

Get in the habit of looking your tank over before each game day. Check for:

• Dents or gouges in the tank body
• Thread damage on the valve or regulator
• Corrosion on CO2 tanks (these are metal and can rust)
• Fiber wrap damage on carbon fiber HPA tanks (fraying, cuts, deep scratches)

If anything looks off, don’t use the tank until it’s been checked by someone qualified.

Don’t Leave Your Tank in a Hot Car

I feel like this shouldn’t need to be said, but I’ve heard enough horror stories. Heat causes gas to expand. A tank sitting in a hot car — especially a CO2 tank — can build pressure well beyond its intended operating range. This has caused burst disks to blow, and in extreme cases, much worse. Bring your gear inside.

Filling at Home: The Personal Compressor Option

If you play frequently enough that fill station trips are a hassle, or you just want the convenience of filling up in your garage, a personal HPA compressor is an option.

What You Need

A paintball-specific high-pressure compressor. These are purpose-built to reach the 3,000-4,500 PSI range that paintball tanks require. Normal shop compressors top out at 100-150 PSI — they’re not even close.

Cost

Expect to spend $300-500 for a basic unit. Higher-end models run $600-1,000+. There are also hand pump options (like a Hill pump) for $200+ that can reach these pressures, but they require significant physical effort — think 15-20 minutes of pumping for a full fill.

Is It Worth It?

It depends on how often you play. If you’re playing every weekend and spending $5 per fill, that’s roughly $250 a year in fill costs alone. A compressor pays for itself in about two years at that rate, and you’ll never have to wait in line at the fill station again.

The convenience factor is real. I know guys who fill up the night before a game so they start every day with a full tank, no waiting around. If you practice at home on a backyard target setup, a personal compressor is practically a requirement.

The downsides: they’re not silent (think small air compressor noise level), they take 5-15 minutes to fill a tank depending on the model, and they require basic maintenance. Some cheaper compressors also run hot and need cool-down periods between fills.

CO2 at Home

Home CO2 filling is possible but less common. You need a bulk CO2 tank (typically 20lb or 50lb) and a fill station adapter. The bulk tank itself costs $100-150 new and can be refilled at welding supply shops for $15-30. One bulk tank will give you dozens of paintball tank fills.

The process is straightforward but requires a scale to fill by weight accurately. Most players who go this route are running CO2-powered markers on a budget and burning through fills quickly.

How Many Shots Per Fill?

Shot count depends on your tank size and your marker’s air efficiency. Here are rough ballpark numbers:

These numbers assume standard semi-auto play with a mid-efficiency marker. If you’re running a mechanically efficient marker like a Tippmann 98 on CO2, you might get more. If you’re running a high-end electronic marker shooting ropes of paint, you’ll get fewer.

For more on costs related to tank fills, paint, entry fees, and everything else, check out my breakdown on how much paintball actually costs.

Picking the Right Tank Size

Tank choice affects how much you spend and how often you’re walking back to the fill station.

For recreational players who go out once or twice a month, a 48/3000 HPA tank is the sweet spot. It’s light, compact, and gives you enough air for several games before needing a refill. Most fields offer unlimited fills, so you’ll just jog over to the fill station between games.

For players who want to minimize trips to the fill station, the 68/4500 is the standard. More air, more shots, more time on the field between fills. The tradeoff is a slightly larger, heavier tank.

For CO2 users, a 20oz tank gives you the best shot count. The 12oz is fine for casual play, but you’ll be refilling more often.

Wrapping Up

Filling a paintball tank isn’t complicated once you’ve done it once. The short version: bring your tank to any paintball field and they’ll handle it. But knowing where else to get fills, understanding the difference between CO2 and HPA fill processes, and staying on top of hydro testing means you’ll never be stuck with an empty tank and nowhere to go.

Keep an eye on your hydro date, don’t leave your tank in the car on a hot day, and if you play enough, seriously consider a home compressor. Your Sunday mornings will thank you.