Gas Cylinder Information and Frequently Asked Questions

Gas and gas cylinder safety

We love you and we want you to stay safe. Please take caution with any compressed gas and gas cylinder.

  • Always make sure the valve is completely closed when you’re done using the cylinder.
  • Keep all cylinders in an upright position
  • Do not expose the tank to extreme weather conditions. High temperatures can increase the cylinder pressure beyond safe limits, causing malfunctions and safety disk bursts


Will this cylinder work for my application?

Honestly, we don’t know for sure. With so many uses for kegs, gas cylinders, and even parts, plus the dangers of improper use, we can’t verify or confirm you’re purchasing the correct items.

It’s up to you. Please make certain that you are purchasing the right and safe item for your intended use before you buy. Your local cylinder filler is an excellent resource for the info you need.

Will this cylinder work with my current regulator?

All of our CO2 tanks have a standard CGA320 valve on them and are compatible with the standard CO2 regulator fitting.

Our nitrogen/Beer Mix cylinders have a CGA580 valve, an inert gas valve used for nitrogen, mixed nitrogen & CO2, and other inert gases (helium, nitrogen, argon). You must use a nitrogen regulator with Beer Mix / nitrogen tanks because the valve and regulators are designed for the higher pressure.

What is the manufacture or certification date of a cylinder?

All cylinders have a manufacture date. Recertified cylinders also have a certification date. The most recent date on the cylinder is the currently active date.

The most important date to know when purchasing a cylinder is when the cylinder was last recertified. Recertification includes hydro-testing. The Department of Transportation (DOT) requires that most portable CO2 tanks, both new and used, be recertified every five years. Nitrogen and other high pressure inert gas cylinders generally have a 10 year recertification requirement (although there are exceptions). Certification must be performed by a DOT-licensed facility.

The date of the last recertification is the 8 digits stamped across the neck of the tank. The first two (which are larger) are the month, and the final two are the year in which the tank was tested. The four smaller numbers in the middle is the DOT registration number of the recertification facility. The cylinders we offer generally have been certified within 180 days from the time of sale.

No matter if you’re purchasing our products for brewing or any of the other thousands of gas applications like getting your weld on, creating a beautiful aquarium, because our prices makes you want to drink, or because you’re filling tires … PLEASE drink responsibly and use caution with any compressed gas cylinder. We’d like to see you again.

What are the exact dimensions of steel CO2 cylinders?

Steel tanks will have variations even when ordering the same size cylinder. Depending on the manufacturer, the cylinder’s dimensions may vary a couple of inches. We give an approximate height and width of the largest typical dimensions.

Can I run straight CO2 from a Beer Mix tank?

Generally, nope:

  • The valve and regulator in a beer mix setup is specific to nitrogen running at a higher pressure
  • With a beer mix tank you would be using a nitrogen regulator on a CO2 tank, and there’s a fitting mismatch (we do have an adapter to allow you to use your nitrogen regulator on a CO2 tank)
  • The valve opening is too large for CO2 regulators
My gas supply is used up too quickly!

That’s not really a question, but take a look at a few things:

  • Check for leaks using a soap and water solution. It will bubble where the leak is. Check the keg as well as the cylinder, as leaks can happen anywhere.
  • Check that the gas disconnect is locked tightly and that the hose is tightly clamped to the regulator.
  • Check to see if your hose clamps are too tight. Overtightening can give the hose a small cut that will leak under pressure.
How many kegs can I pour from my cylinder?

Generally, it takes about half a pound of CO2 to pour a quarter barrel of beer, and one pound to pour a half barrel.

Here’s some approximate numbers to help you choose the right size for your setup – choose the keg size, and click to find out the pours per cylinder size. Your actual results may vary.

5 Gallon Keg

2.5 lb. cylinder = 7 to 11 kegs

5 lb. cylinder = 15 to 22 kegs

10 lb. cylinder = 31 to 44 kegs

15 lb. cylinder = 46 to 66 kegs

20 lb. cylinder = 62 to 87 kegs

Sixth Barrel (5.23 Gallon) Keg

2.5 lb. cylinder = 7 to 11 kegs

5 lb. cylinder = 14 to 21 kegs

10 lb. cylinder = 29 to 42 kegs

15 lb. cylinder = 44 to 63 kegs

20 lb. cylinder = 59 to 83 kegs

Quarter Barrel (7.75 Gallon) Keg

2.5 lb. cylinder = 5 to 7 kegs

5 lb. cylinder = 10 to 14 kegs

10 lb. cylinder = 20 to 28 kegs

15 lb. cylinder = 30 to 42 kegs

20 lb. cylinder = 40 to 56 kegs

Half Barrel (15.5 Gallon) Keg

2.5 lb. cylinder = 2 to 4 kegs

5 lb. cylinder = 5 to 7 kegs

10 lb. cylinder = 10 to 14 kegs

15 lb. cylinder = 15 to 21 kegs

20 lb. cylinder = 20 to 28 kegs

Note that a properly filled cylinder should read ~750 PSIG at 72 degrees. Pressure will increase as heat increases, and go down as the temperature goes down.

Tank should read ~750 PSIG until the liquid CO2 is gone and the cylinder is almost empty. Decreasing pressure is telling you the cylinder is almost done.

Got any tips for serving nitro or cold brew coffee from my kit?

Cold Brew and Nitrogen-Infused Coffee Tips

Coffee is a very personal expression of taste and art. We’d never presume to know more than you about cold brewing your coffee, so we’ll leave that part up to you. Once it’s brewed, though, we can help you serve it up from your new kit.

General Cold Brew and Nitro Coffee Pointers

Always make sure that the coffee you add to your keg is free from grounds and other debris. This keeps lines and faucet flowing smoothly. It’s particularly important for nitro coffee taps. They have a perforated disc inside the tap body (it creates that great infusion/cascade) that can clog easily.

Nitrogen cylinders can be filled at welding supply stores, gas suppliers, and some homebrew stores.
Keep your coffee fresh by cleaning your lines, tap, and keg regularly. Cleaning instructions can be found on our site under Info > Instructions.

For Cold Brew Coffee Only

Cold brew coffee requires very low nitrogen gas pressures to deliver smoothly. Start with your regulator set around 5 PSI and experiment up and down until you get the pour you want.

Cold brew coffee is dispensed through normal beer faucets. They have no internal restrictions, so if your pressure is too high, you’ll get a foamy coffee bath. Again, start low, work up.

You do not need to take any special steps to infuse your coffee with nitrogen. Nitrogen only provides pressure to get it from keg to tap.

For Nitro Coffee Only

You’re serving coffee that is infused with nitrogen – and you must do the infusing. Two ways to do it:

  • The “works OK” way: Fill the keg with coffee, connect the gas, pressurize it (35-40 PSI), and shake it/roll it around on the floor or your knee for quite a while. Yes, we’re serious. This gets the nitrogen into the liquid. You’ll need to do this every 4-6 hours to keep the infusion up. Note: be very careful if you choose to use this method. Kegs are heavy and the keg and cylinder are under substantial gas pressure. Exercise caution to protect yourself and those around you.
  • The best way: Use what the beer guys call a “carbonation lid.” For you, it’s an infusion lid. The lid has a gas connection point that leads to a length of hose with a finely perforated stone on the end. This reaches to the bottom of your keg and bubbles the nitrogen up from below, infusing it with tiny nitrogen bubbles as it goes. Low (5-6 PSI) pressure and about 20 minutes is all that’s required to infuse the coffee; more time may be required to reach serving pressure in the keg. This is a lot less difficult than the first method, and much easier to freshen up throughout the day. They’re available on our site under the Cold Brew and Nitro Coffee Kegs menu or at

Important note: nitrogen doesn’t want to stay infused in a liquid. The moment you put it in, it’s trying to separate back out.

You will need to re-infuse the coffee at intervals throughout the day. You’ll know it’s time when the cascade stops happening, and as you get more experience you’ll learn the intervals that work best for you and the results you want.

Nitrogen pressure for pouring nitro-infused coffee is much higher than cold brew. Start at 35 PSI and experiment until you get the feel and froth you like.

Gas Cylinder Information

Steel versus aluminum cylinders

Steel cylinders are more economical but significantly heavier than aluminum. Aluminum is more rust- and corrosion-resistant than steel, which is important for wet gases and in humid or condensation-prone environments.

For CO2 cylinders, both use valves with a CGA320 outlet but have different inlet characteristics, so take note if you are replacing the valve

CO2 versus Beer Mix

Most brewers start with straight CO2 to carbonate and push their delightful brews. Heavier stout and Guinness-style beers require a mixture of gases blended perfectly to achieve best results. Most beer gas users prefer a blend of 75% nitrogen 25% CO2, but there are variations that your filler can supply. Straight nitrogen is also an option.

Siphon tubes and CO2 cylinders

We offer siphon tube installation for specialized applications that require liquid CO2. Although there are various uses for siphon tubes, they are typically installed in larger tanks (such as our 35 lb. and 50 lb. CO2 cylinders) and can be used for refilling smaller CO2 cylinders.

If you would like to add siphon tube installation to your cylinder order, selecting it separately and add it to your cart. Please note it will take an additional two to three business days to install and ship, and there is an extra charge for installation. You will know the siphon tube has been installed because the letters ‘ET’ will have been stamped on the neck of the valve.

Note: There are additional external components needed to complete transfer to a smaller tank. We don’t carry those parts, and we can’t confirm what items are necessary to complete the refill. Please make sure you have the correct parts, knowledge, and skill before attempting to refill any gas cylinder.

UN/ISO vs DOT/TC cylinder markings

All cylinders must be manufactured and certified to a recognized standard. The US Department of Transportation (DOT), Transport Canada (TC), and UN/ISO all have established cylinder standards.

UN/ISO standards are newer than DOT/TC standards, and UN/ISO cylinders are equivalent to and in many ways superior to DOT/TC-rated cylinders:

  • UN/ISO is a universally recognized worldwide regulation for compressed gas cylinders, and UN/ISO cylinders are approved for use in almost every country around the world. UN/ISO cylinders can cross country borders and still be filled easily.
  • UN/ISO service pressure is at or above the common fill pressure of a DOT cylinder with a +10% overfill designation. These higher capacities allow for UN/ISO cylinders to be easily integrated into a fleet of DOT/TC cylinders.
  • UN/ISO cylinders contain friendly markings with service pressures rated in PSI and bar.
  • UN/ISO cylinders remain in circulation at maximum capacity for the life of the tank. Due to the higher design ratings for pressure, UN/ISO cylinders do not require REE (Rejection Elastic Expansion) testing to achieve the common cylinder service pressures used and approved in North America. While REE is a valuable and stringent test, DOT/TC cylinders will often have their maximum fill pressure ratings reduced after testing.

Facts and differences between UN/ISO and DOT/TC requirements

  • Gas fillers in the USA can legally fill UN/ISO and DOT/TC cylinders that meet CFR regulations.
  • UN/ISO and DOT/TC cylinders are manufactured in the U.S. and other foreign countries.
  • DOT/TC and UN/ISO cylinders have the same dimensions, internal water volume, steel chemistry, and valve compatibility.
  • UN/ISO cylinders have a higher working pressure and gas volume capacity than DOT/TC cylinders.
  • DOT/TC-stamped cylinders are acceptable for transport to, from, and within the U.S. UN/ISO-stamped cylinders must have “USA” country-of-approval marking to be acceptable for transport to, from, or within the U.S. Our UN/ISO cylinders are stamped “USA”.
  • DOT/TC markings must conform to the applicable requirements of 49 CFR 178.35, and UN/ISO pressure receptacles markings must conform to the applicable requirements of 49 CFR 178.71.
  • DOT/TC and UN/ISO cylinder markings are expressed in conventional units.
  • DOT/TC date of manufacture is expressed as month-year (10-13), while UN/ISO is stamped year (4 digits) and month (2013/01)
  • DOT/TC stamps service pressure only in PSI. UN/ISO cylinders have stamps for both service pressure (PW) and test pressure (PH) in bar and PSI.
  • DOT/TC does not require inlet thread profile to be stamped. UN/ISO requires the inlet thread profile to be stamped.
  • The manufacturer approval number granted by U.S. Department of Transportation (Pipeline and Hazardous Materials Safety Administration) is required by both the DOT/TC and UN/ISO. If manufactured in the same facility, the approval number will be the same.
  • Third-party independent inspection is required for both DOT/TC and UN/ISO designs.
  • There is no plus or star for UN/ISO cylinders. The service pressure is already at or above the 10% overfill authorized for select gas services by DOT/TC.

If you or your filler has any issues filling a UN/ISO cylinder, please contact us and we will assist you in getting the cylinder filled.

A diagram of UN/ISO cylinder markings can be found here.