Cask ale is where your gross profit quietly bleeds out. Every operator knows they lose beer on cask — the question almost nobody can answer is how much, and exactly where. A keg is forgiving; cask punishes you for every mistake. It throws sediment, it has a three-day clock ticking the moment you vent it, and it hides losses in ullage that never show up on the till. After years of running cask through my own pub I can tell you the money doesn’t vanish — it leaks from a handful of very predictable places. Here is the complete map of where cask money disappears, how much loss is actually “normal,” and how to plug it.
Key takeaways
- Cask wastage runs higher than keg: a well-run keg loses ~3–5%; cask routinely loses more once you add sediment, the 3-day clock and short pulls.
- A 72-pint firkin yields only about 66 saleable pints — build that ~8% straight into your expectations or every cask looks like a loss.
- The biggest leaks are sediment/ullage, the 3-day shelf-life clock, over-pour, line losses, and warm cellar temperature — in that order.
- You can often reclaim beer duty on genuinely spoilt cask (HMRC duty credit) — most pubs never bother and leave money on the table.
- You cannot control what you do not measure: track cask line-by-line and the leaks become obvious.
Where cask money actually disappears (the loss map)
Run down this list in order — it is roughly the order of how much each one costs you.
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1. Sediment & ullage
Cask is a living product: it drops a sediment of yeast and finings, and the bottom of every cask is unsaleable. That is why a 72-pint firkin only gives ~66 sellable pints. The brewer is even allowed to under-fill slightly — Excise rules let them include around 2.49 pints of allowance in a 36-gallon barrel (less in smaller casks). None of that is theft or error — but if you do not allow for it, your stock results will show a phantom loss on every single cask.
2. The three-day clock
The moment a cask is vented and tapped, the clock starts. Cask ale is typically at its best for about three days on the stillage once broached. Sell through it in that window and you make your margin; let it run past and you are pouring profit down the drain. The single most expensive cask habit in the trade is putting on a firkin you cannot sell in three days “because it was on offer.” Match your cask range to your real throughput, not your optimism.
3. Over-pour & short measure
Cask is hand-pulled, so the pour depends entirely on the person behind the bar. A heavy-handed pull, a full head topped up to a brim, a “taste” for a regular — each is a few pence, but across a busy session they add up to pints. This is also where genuine loss (over-generous staff) blurs into genuine theft (unrecorded pours). You cannot tell the two apart by feel — only by measuring expected vs actual.
4. Line losses & cleaning
Every line clean pulls beer to waste, and cask lines are often cleaned more frequently. The industry rule of thumb for line cleaning, ullage and general wastage combined is roughly 0.5%–1.5% of net wet sales — if you are well above that, your cleaning routine or your throughput is the problem.
5. Warm cellar = faster loss
Cask wants a steady cellar temperature of around 11–13°C. Too warm and the beer goes over faster, hazes, and ends up as ullage before you have sold it. A drifting cellar temperature is a silent multiplier on every other loss on this list. A simple cellar thermometer or wireless temperature monitor is the cheapest insurance against cask wastage there is.
How much cask wastage is “normal”?
There is no single magic number, but here is the realistic benchmark ladder:
| Dispense | Typical wastage |
|---|---|
| Well-set-up keg, short lines | 3–5% |
| Cask, well managed | ~5–8% (incl. sediment/ullage) |
| Party pumps / uncertain pouring | 8–12% |
| Cask, poorly managed / slow throughput | 10%+ |
If your cask is running into double figures every week, it is almost never “just how cask is” — it is throughput, cellar temperature, or pour discipline. The figure itself is less important than the trend: track it weekly and a creeping number tells you something has changed before it costs you a fortune.
Reclaim the duty on spoilt cask
Here is the bit most operators miss: when cask genuinely goes off, you can often reclaim the beer duty on it through HMRC’s spoilt-beer duty credit scheme (and tied tenants have specific routes via the Pubs Code). It will not make a bad cask profitable, but the duty back on genuine ullage is real money you are entitled to — provided you have recorded the wastage properly. Another reason measuring beats guessing.
You can’t control what you don’t measure
Every leak above is invisible until you put a number on it. That means two things: measuring what is actually left in a part-used cask, and tracking expected vs actual week on week. For the measuring, see our full guide on how to measure a part-used keg or cask with a dipstick — a calibrated cask dipstick takes the guesswork out of every partial. For the tracking, StockTap is the stock-take app I built for my own pub: it converts your dip readings to saleable pints, values the cask, and shows your cask GP line by line so the leaks stop hiding. One-off £97. See how StockTap works →
Cask vs keg — which actually makes you money?
Cask carries a romance that keg does not, and for the right pub it builds a crowd. But be honest about the economics: cask demands more cellar work, more skill, and carries more wastage risk than keg. If your cask is well-run and selling through in three days, it earns its place. If it is limping along at 10%+ wastage to keep three handpulls looking busy, you are subsidising image with GP. Measure both, compare the real margins, and let the numbers — not the handpull — decide your range.
Frequently asked questions
How much wastage is normal for cask ale?
A well-managed cask typically loses around 5–8% once sediment and ullage are included — higher than a keg’s 3–5%. Double figures usually signals a throughput, temperature or pour-discipline problem rather than “just cask.”
Why does a firkin only give 66 pints?
A 72-pint firkin drops a sediment of yeast and finings, and the bottom of the cask is unsaleable. Around 6 pints per firkin is lost to sediment and ullage, leaving ~66 saleable.
How long does cask ale last once tapped?
Roughly three days at its best once vented and broached. Match your cask range to what you can sell in that window.
Can I claim duty back on wasted cask beer?
Often yes — HMRC operates a spoilt-beer duty credit scheme, and tied tenants have routes via the Pubs Code. You must have recorded the wastage properly to claim.
What cellar temperature stops cask wastage?
Keep the cellar steady at around 11–13°C. Warmer than that and cask goes over faster, turning saleable beer into ullage.
Disclosure: some links above are affiliate links to Amazon. If you buy through them I may earn a small commission at no extra cost to you. I only link to kit I would actually use in my own cellar.
Related cask & cellar guides
- How to count cask ale stock
- How to measure a part-used keg or cask (dipstick & weight)
- Beer keg measurement chart
- How to manage your pub cellar
- Marston’s line check explained
- Stonegate line check explained
- The weekly pub stock check
See also our UK keg guide — the top draught beers, pints per keg, and how to work out the GP on every line.
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