Why is my beer fobbing? The nine causes, how to find yours in five minutes, and what the drip tray costs

Why is my beer fobbing? Nine times out of ten it's temperature, gas or time: a cellar warmer than 11 to 13°C, a cooler that's run out of ice, a keg put on before it's settled for 48 hours, a keg left on longer than five days, or gas left on overnight. Dirty lines, hot glasses straight from the washer and pouring too fast cause most of the rest. Work out which by asking one question first: is it every line, one line, or only at certain times?

Cask Marque, quoting The Publican, says fobbing is the most common fault on beer dispense, 39% of them, and puts a number on it that every licensee should see once. One drip tray of fob per tap per day is about a pint and a half. On ten taps that's 5,475 pints a year. At around £2 a pint cost, which is roughly what a standard pint costs a pub before VAT and margin, that's about £10,950 of beer poured down the drain, and none of it shows up anywhere except as a hole in your stocktake.

Most guides give you a list of causes and leave you to it. Here's the list, but sorted the way you'd actually find the fault, by where the fob is happening.

Start here: where is the fob?

Finding the fault by where it shows up (my reading of the brewer and Cask Marque guidance below)

What you see	Most likely cause	First thing to check
Every keg line fobbing at once	Cellar too warm, remote cooler off or low on water or ice, wrong gas	Cellar thermometer, cooler switched on, water and ice bank level, the cylinder on the board
One line only	That keg: over-conditioned, warm, on too long or not settled, or that line dirty or kinked	Date on the keg, when the line was last cleaned, the python and the coupler
Straight after a keg change	New keg not had its 48 hours in the cellar, or a stuck fob detector	When it was delivered, and the float in the fob detector
First pint or two after a quiet spell	Beer warming up in the line between pulls	Pull the first one into a jug and see if the second is fine
Only on a busy night	Cooler can't keep up, or staff pouring faster to keep up	Cooler capacity and ice bank, pouring technique
Only in some glasses	Hot or dirty glasses	Glasses straight out of the washer, rinse aid, how they're dried

The causes, one by one

1. The cellar is the wrong temperature

Cask Marque, Tennent's and the Enterprise technical guide all give the same figure: keep the cellar at 11 to 13°C, all the time. Above 13°C keg beer fobs and cask beer spoils. It works the other way too, too cold can upset dispense and put a chill haze in cask. Put a thermometer in the cellar and write the temperature down every day. My free fridge and cellar temperature log has a sheet for it.

2. The remote cooler is off, low or struggling

Keg beer is chilled on its way to the bar by the remote cooler, not by the cellar. The Enterprise guide says keep it switched on, and keep an eye on the ice bank, glycol and water levels, because the wrong temperature or low water causes fobbing and waste. If every keg line goes at once on a hot day or a busy Saturday, the cooler is the first suspect. Tennent's warns not to top up the sealed type of cooler yourself, those normally carry a label saying so.

3. The keg went on too soon

A keg that's come off a warm lorry needs time to come down to cellar temperature. Tennent's and the Enterprise guide both say 48 hours in a cooled cellar before you connect it. Rotate so the oldest delivery goes on first and there's always one settled keg behind the one on sale. If you're having to put kegs on the day they arrive, your par levels are too tight, and the par levels guide shows how to set them.

4. The keg's been on too long

Cask Marque says a keg left on sale longer than about five days absorbs too much gas, and that's fob. Tennent's says the same: after five days taste and aroma change and fobbing or flat pours get more likely. On a slow line that's a real problem, and it's one of the reasons I'd rather have fewer lines than more. The sums are in how many draught lines a pub needs.

5. Gas left on between sessions

Turn it off when you're closed. Cask Marque lists gas left on between trading sessions as a cause of fobbing, and Tennent's adds the condition that matters: only do it in a refrigerated cellar. While you're there, check it's the right gas. Inn Express's fitment guide lists 30/70 mixed gas for bitters and stouts and CO2 or 40/60 mixed for lagers, ciders and pale ales, and says to check the brand owner's own recommendation. The wrong cylinder on the board will fob a keg or flatten it. The cellar gas guide has the mixes and the cost per pint.

6. Dirty or kinked lines

Yeast builds up in lines and knocks the gas out of the beer. Clean every seven days, which is the Cask Marque standard and the one most brewers write into their guidance. A kinked line does the same job, mostly on cask. The waste from a line clean is real but it's planned waste. Fob from a dirty line is waste you're paying for twice. I go through the cost of both in beer line cleaning and your variance.

7. The pressure or the flow is wrong

Don't touch the regulator. Tennent's says a technician should set the pressure and nobody else should change it, and the Enterprise guide says the same: call the brewer if you think the mix or pressure is wrong. Turning the gas up to make a slow tap go faster is how a lot of fob starts. The fix for a slow tap is usually the flow setting at the font or the tap itself, and that's a tech job too.

8. The glass or the pour

The Enterprise guide lists hot glasses and dispensing too quickly. A glass straight out of the washer is warm and the beer fobs the second it hits it. Have a rack cooling and use those first. Tennent's adds the wrong creamer and poor-condition glassware. A greasy glass kills the head, a scratched one makes it rise and rise, and both end up in the drip tray.

9. A stuck fob detector

The fob detector is the little bowl with a float that stops gas and foam going up the line when a keg runs out. The Enterprise guide says if the float sticks, release it with the button at the base and make sure it's left in the down position. If it isn't reset properly after a keg change, the first few pints come up as fob.

What fob costs you

Fob at a pint and a half per tap per day, at about £2 a pint cost (Cask Marque's rate, my arithmetic)

Keg taps	Pints a year	At cost, about £2 a pint	At a £5.34 selling price
4	2,190	£4,380	£11,695
6	3,285	£6,570	£17,542
10	5,475	£10,950	£29,237

The selling price column only applies if you'd have sold that beer, which you would if the keg runs dry before the week does. Either way it's a lot of money for a drip tray. And it's money that turns up in the stocktake looking exactly like a pouring problem or a missing pint, which is why I always want fob ruled out before anyone starts looking at the staff. The draught wastage guide covers what's normal for the rest.

The idea nobody does: measure the fob

Everybody guesses at fob. Nobody measures it. So for one week, at the end of every session, tip each drip tray into a measuring jug before it goes down the sink, and write the amount on the wastage sheet against the line it came from. It takes a minute a session.

At the end of the week you'll know three things you didn't before. Which line is the problem. Whether it's every day or only busy days, which tells you if it's the cooler. And how many pints you're actually losing, which you can hold up against the stocktake variance. If one line is giving you three pints a day and the rest half a pint, you don't need an engineer to tell you where to look. If they're all bad on a Saturday and fine on a Tuesday, ring about the cooler.

Never pour drip tray beer back into anything. Measure it, log it, tip it.

When to call the brewer

If you've checked the cellar temperature, the cooler, the gas and the lines and it's still fobbing, ring the brand owner or your lead brewer. The Enterprise guide says exactly that. Keep your week of drip tray measurements to hand when you do, because "line 3 is losing two and a half pints a day and it started on Tuesday" gets a technician out a lot faster than "the Carling's a bit lively". If you're in a Cask Marque audit or thinking about one, cellar temperature and lines are two of the four places pubs lose stars.

Common questions

Why is my beer fobbing?

Usually temperature, gas or time: a cellar warmer than 11 to 13°C, a remote cooler low on ice or water, a keg connected before it's had 48 hours in the cellar, a keg on sale longer than about five days, or gas left on between sessions. Dirty lines, hot glasses and pouring too fast cause most of the rest.

What temperature should a pub cellar be?

11 to 13°C, all the time. Cask Marque, Tennent's and the Enterprise technical guide all give that range. Above 13°C keg beer fobs and cask beer spoils.

Why is only one line fobbing?

If it's one line, it's that keg or that line: the keg may be warm, over-conditioned, not settled or on too long, or the line may be dirty or kinked. If every line fobs at once, look at the cellar temperature, the remote cooler and the gas.

Should I turn the gas off at night?

Cask Marque lists gas left on between sessions as a cause of fobbing. Tennent's says turn it off when a keg isn't in use, but only in a refrigerated cellar.

How much does fobbing cost a pub?

Cask Marque's example is a drip tray of fob, about 1.5 pints, per tap per day. On six taps at about £2 a pint cost that's roughly £6,570 a year.

Can I turn the gas pressure up to stop a slow tap?

No. Tennent's and the Enterprise guide both say the pressure should be set by a technician and not changed by anyone else. Turning the gas up to speed up a tap often causes fobbing.