Equipment
Kegs, couplers and dispense
What kinds of keg are used for cider and how do the fittings work?
In short
The standard trade keg is a stainless steel vessel with a single central spear: a combined gas inlet and liquid outlet with a dip tube reaching the bottom, opened by a coupler pressed and locked onto the neck.
Gas — usually carbon dioxide, sometimes a carbon dioxide and nitrogen mix — enters around the spear, pressurises the headspace and pushes cider up the dip tube to the tap.
Kegs are pressure vessels with a stated maximum working pressure and a required inspection regime, and the fittings are not interchangeable between designs.
Keg and coupler types
The last row matters for cider particularly. A great deal of traditional draught cider is served from a vented cask by gravity, which is a fundamentally different arrangement from keg dispense: no applied gas, a naturally still or lightly conditioned product, and a short shelf life once broached. Both are legitimate and they suit different ciders.
| Keg type | Fitting | Typical use | Notes |
|---|---|---|---|
| Steel keg with a spear | Coupler types designated S, D, A, G, U, M and others by valve geometry | Trade dispense across cider, beer and soft drinks | The coupler must match the spear; forcing the wrong one damages the valve |
| Cornelius keg | Separate gas and liquid posts, ball-lock or pin-lock | Small-scale and craft dispense; originally soft drinks | Two posts, two disconnects; easy to open and clean by hand |
| One-way composite or bag-in-keg | A spear fitting on a plastic body containing an inner bag | Export and one-way trade | Gas never touches the cider; not refillable, so it is a packaging cost not an asset |
| Traditional cask | Shive and keystone, tapped with a wooden or plastic tap | Traditional draught cider dispensed without applied gas | Not a pressure vessel; vented to atmosphere and served by gravity or beer engine |
Cleaning a keg
A keg with a spear cannot be cleaned by looking into it, because there is no opening a person can reach through. Cleaning is done by machine or by circulating solution through the spear: a keg washer removes the residual product, rinses, circulates detergent, rinses again, sanitises and purges with steam or gas. Doing this properly is the whole business of keg hygiene, and it is why kegs are usually washed on dedicated equipment rather than improvised.
The spear itself is the hard part. It has an internal seal, a spring and an annular gas passage, and product sits in all of them. Spears are periodically removed for inspection and seal replacement, using the correct tool.
Removing a spear is a task with a specific hazard, treated below. Cornelius kegs avoid the whole problem by having a large removable lid, which is the main reason they are the usual choice at small scale despite being an older and less efficient design.
Gas, pressure and dispense balance
The applied gas pressure does two jobs at once, and they conflict. It pushes the cider out, and it also determines the equilibrium carbonation of the cider in the keg. Too little pressure and the cider gradually loses its gas into the headspace and pours flat; too much and it over-carbonates and the tap pours foam. The pressure that balances these is set by the carbonation level wanted and the temperature of the cellar, and dispense line length and bore are then chosen to drop the remaining pressure so the cider arrives at the tap at atmospheric.
This is why a keg that pours foam is usually not a keg problem. It is a temperature problem, a line problem, or a pressure that has been turned up to force a slow pour and has carbonated the product instead.
Mixed gas is used where a cider is to be dispensed at a pressure higher than its carbonation would tolerate, typically on a long line. Nitrogen is far less soluble than carbon dioxide, so it can supply push without adding carbonation.
Keg pressure safety
Also answered on this page
Questions this page covers, so you can tell at a glance whether it is the one you want.
- What coupler does a cider keg use?
- Why does my keg pour foam?
- How do you clean a keg?
Related
What people ask next
Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.
- How do i sterilise cider bottles — Wash them clean first, then sanitise with a no-rinse sanitiser or a sulphite solution, and fill while still wet with it. Bottles that look clean but have dried deposits inside are the usual source of bottle spoilage.
- How is cider carbonated — Either by dissolving carbon dioxide into finished cider under pressure, or by letting a small second fermentation produce the gas inside a sealed bottle or tank. The first is faster and more repeatable; the second leaves sediment and a finer bead.
- How should i store cider — Cool, dark and at a steady temperature. Light causes light-strike in clear glass, warmth accelerates oxidation, and temperature swings push cider past the closure of a bottle that is not tightly sealed.
- What is traditional draught cider — Still or lightly conditioned cider served from a cask or a bag-in-box rather than under gas pressure, so whatever sparkle it has came from its own fermentation. It is the format most West Country farmhouse cider is sold in.
- Where does the fizz in cider come from — Either from fermentation trapped in a sealed container, or from carbon dioxide dissolved into the cider under pressure before filling. The French cider appellations permit only the first, and require at least 1.0 to 1.5 bar at 20 °C depending on the name.
- Why is my bottled cider flat — Either there was no viable yeast left to ferment the priming sugar, or the bottles are not sealing, or it is simply too cold and needs longer somewhere warmer. Two to three weeks at room temperature is the usual minimum.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
National Association of Cider Makers
NACM · specialist organisation · retrieved 2026-08-24
The UK trade association. Useful for industry-agreed definitions and for the voluntary labelling standards its members work to. A trade body has an interest in how its product is described, so CiderHQ cites it for what the industry says about itself rather than for neutral scientific claims.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
Where to go next
- Cider making equipment — The rest of the equipment material, grouped by what each piece is for.
- How cider is made — The methods this equipment exists to carry out.
- Troubleshooting — The faults that are traced back to equipment and to cleaning.