Keg Beer Pressure in the UK

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10 thoughts on “Keg Beer Pressure in the UK

  1. Another very good post Yvan, let’s hope it leads to improvements all around for the benefit of all. Especially the safety advice on max pressures with non metal kegs !

    Cheers, Steve

  2. It amazes me that servers that have so much passion for beer can have little to no understanding of the cellar and gas workings. Hell I spent so much time down there cooling off with a hangover I got a good grounding before I started

  3. Heya, great post. Would love some advice on venting overcarbed steel kegs? Also, does draw length not play into your recommended PSI calculator at all?

    • VENTING: If I ever get the time I’ll do some stuff re venting kegs. It needs a video really. The difference between KeyKeg and top-pressure kegs is the former is vented via the beer-out side of the coupler and the latter via the gas-in side.

      To vent via the gas-in side you need to take out the no-return “duck bill” valve from the connector. (Unscrew the pushfit fitting, take out the rubber bit, screw pushfit back on.)

      Then I attach a couple of feet of line with a flow restrictor on the end, fully restricted, then attach coupler. Use flow restrictor to carefully let off all CO2 pressure from headspace.

      I tend to also have a pressure gauge as part of this, so I can let off CO2 in steps until a desirable pressure to achieved. Letting the keg return to equalibrium after each venging. It doesn’t take a lot of hands-on time,but the process can take a few days if you’re being careful. You can get away with being less careful as with top-pressure keg you can re-carbonate at least.

      [Keep a coupler set up like this in your toolset as a “venting coupler”.]

      • All very helpful, thank you. I’ve used a system with flojets which had easily accessible flow controls, but with 100% CO2, now am on 60/40 without flojets and the flow controls haven’t been well-placed, so have become aware of some of the advantages and disadvantages of each aspect.

        • I’d personally build a system for straight CO2, flowjets if needed (using compressed air), and a flow-control close to or on the tap. Would have a compressed air supply for both flojets and keykegs. I’ve recently bought a load of US Perlick taps with FC on the tap, looking forward to using them… they are recommended by Stu at Magic Rock so are almost certainly “the shit”…

          One customer of mine recently had a “craft beer” install with no gauges and to add insult to injury the flow controllers are hidden behind a wall that isn’t trivial to remove to access them. Customer knew no better of course and used the “professionals”…. ho hum.

    • Draw Length: Line resistance from line length and height delta impacts flow – and in US texts is used as a form of flow control. (Coil 8′ of 3/16 line in keggerator, etc)

      What your line resistance tells you is that you may need more pressure to get the beer flowing out the tap. But you cannot simply bump up CO2 pressure… if you need more pressure you need to go to mixed gas so you can get the pressure up but not change the carbonation.

      However commonly in the UK two things are used to make this different to what you’ll find in US texts. First FloJet pumps are used on beer lines to get around needing to use pressure to overcome line resistance. (So you don’t need to add pressure to “push” beer.) Second we use flow restrictors on everything generally. (So you don’t need to add line-length to slow-down beer.)

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  5. Yvan,

    Just saw this when searching for a carbonation chart. Thanks for putting it together…

    The biggest thing to get right, which you explain, is to get the correct head pressure set for the temperature of the beer in the cellar and the brewery’s target Volumes. Then and only then should you worry about balancing that with line resistance.

    If you pressure is 17psi on the keg that needs balancing with 17psi worth of resistance. You can cheat with flow controls, but I find them the source of many callouts and try to rely on the line resistance. The standard lines that we use here from Valpar have the following resistances:

    Valpar 3/8 OD x .265″ MDP Tube = .13 psi/foot (.43 psi/metre)
    Valpar 3/16 OD x .117″ MDP Tube = 5.8 psi/foot (19 psi/metre)

    and you also must consider any height difference between keg and tap. The resistance from height is .5 psi/foot (1.64 psi/meter)

    Typically the 3/8 run length and the height are known variables, therefore you will have the resistance they provide….then you make up the difference with the 3/16 (choker) line at the tap.

    Hope that makes sense.


    • Sorry, very delayed in noticing the comment – this old blog is a bit neglected.

      Yes, everything you say makes sense. Top-pressure is purely about carbonation as far as I’m concerned.

      And it (plus temperature) is one variable along with line resistance, lift, and flow control in getting beer coming out of a tap right.

      If your top-pressure for correct carbonation is good enough to dispense the beer, great! – if not then flojets or mixed gas are your options.

      I take all of this into account when installing a draught system of course.

      Life is so much simpler with coldstore based direct draw systems of course… 12C cellars, flash chillers, long python runs, shitting python cooling… it’s no wonder dispense in pubs for keg is such a nightmare really.

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