Beer Gas the Cellar and Colour Coding

Mixed Gas Bottle 30/70

Is it possible to use the wrong gas in your cellar? No you say there are different fittings for Co2 and mixed gasses. But if you didn’t know already there are at least three different blends of mixed gas used in the cellar. So it is possible to connect the wrong blend of mixed gas.

We can start by identifying the different coloured gas pipe used across your cellar equipment.

Blue Pipe:

Air from the air compressor. Used to drive the gas pumps.

Grey Pipe:

Co2 Gas – used these days primarily for lager and Ciders, and maybe a few bitters. Some breweries insist Co2 is used so as not to change the taste of their beers.  And a electric or gas pump is then used to pump the beer to the tap.

Green Pipe:

Mixed Gas 30/70 – used for dispensing Guinness, Mild and Smooth-flow bitters. Nitrogen is now added in the brewing process to make the Smooth-flow bitters creamier.

Purple Pipe:

Mixed Gas  50/50 – used for dispensing Lager and Ciders, however you will find white pipe more commonly used.

White Pipe:

Mixed Gas  60/40 – used for dispensing Lager and Ciders

Mixed gas is a blend of Co2 and Nitrogen, in beer dispense Co2 holds the gas in suspension by being at a slightly higher pressure than the top pressure in the container while Nitrogen unlike Co2 does not get absorbed into the beer, so is used to push it up the line to the tap.

Check colour coding as well as the label

The first digits of the bottle labelling represented Co2 followed by the nitrogen. So Mixed Gas 30/70 would be 30% Co2 / 70% Nitrogen and Mixed Gas 60/40 would be 60% Co2 / 40% Nitrogen. But I now see some gas companies marking their labels the other way around. So perhaps someone could clarify this. So to be safe, always look for the colour coding as well.

Now I come to whole point of this article, Always make sure you use the right mixed gas bottle because it is possible to connect a Mixed Gas 60/40 bottle to a Mixed Gas 30/70 system, and if you do and do not notice straight away, it will cost you some serious money because it will make all your Guinness, Mild and Bitters containers un-servable you will see fobbing on a scale you have never seen before.

This usually happens in a Pub that doesn’t use 60/40 gas. The Landlord relies on the gas company to supply the right gas, but as you know in the real world anything can happen labels drop off etc. So always check and if in any doubt ring your supplier. One of these days they may start using different bottles for the different blends but I can’t see that happening for a very long time, so be vigilant.


  1. I always understood that if there is more than 30precent co2 with a balance of nitrogen the co2 will precipitate out of the mix. So depending on the temperature wth a 50/50 ‘mix’ you’ll
    actually only get 30co2/70n2 out of the top of the bottle and 100% co2 when you get to the bottom or vice versa if a dip tube is used. To get a stable co2/n2 mix of greater than 30% CO2. you need to mix on site with a blender.

  2. I have had a member of staff use a 60/40 gas on john smiths which is usually 30/70, is there anything that can be done or will the rest of that keg fob?

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