Why the first pint of the day from a tap can taste off

Beer waits in the lines overnight

Between the keg and your glass is a length of tubing, sometimes a metre or two, sometimes 30 metres or more in a big bar. All of that tube is full of beer when the bar closes. A thin 3/16 inch line holds roughly 18 ml per metre. A wider trunk line holds about 70 ml per metre. On a long system, there can be well over a litre of beer sitting still in each line.

That beer has been away from the cold keg for hours. Whether it still tastes right depends on how well the line is cooled and how clean it is.

Warm lines give warm, foamy pints

In a good system, the lines are cooled all the way to the tap. In many bars, the last stretch through the bar counter and up into the tap tower is not. Overnight, in an Indian city where the bar may sit at 28 °C with the air conditioning off, that last stretch warms up.

Warm beer holds less CO2. When it is poured, gas breaks out, the first glass foams and the beer that remains tastes flatter and warmer than it should. A well run bar pours this first warm beer away before serving anyone.

The tap itself can add stale notes

The faucet and nozzle hold a little beer after the last pour. Overnight it drips, dries and leaves a sticky film. In warm humid weather, that film is a happy home for bacteria and wild yeast. The first pour of the day washes some of it into the glass.

The result can be a faint sour, buttery or musty edge, or simply a beer that tastes tired. Bars that soak nozzles overnight and plug the taps avoid most of this. Our guide to signs of a badly kept pint lists what to look for.

Dirty lines make it worse

Beer lines need a full chemical clean about every two weeks. Between cleans, a thin layer of yeast, protein and bacteria builds on the inside of the tube. Beer moving through quickly picks up little from it. Beer sitting still against it for 12 hours picks up much more.

The giveaway is a first pint with a buttery, butterscotch note (diacetyl, often from bacteria in the line) or a vinegar sharpness. If the second and third pints taste cleaner, the line is due a clean.

Hot weather makes every part of this worse

Each of these problems speeds up with heat. A line that sits at 18 °C overnight in a hill station bar gives a much better first pint than the same line at 30 °C in a coastal city in May. Bacteria grow faster, CO2 escapes faster and residue in the tap dries and sours faster.

That is why bars in hot cities need to be stricter than the textbook, not more relaxed. Taps plugged with a clean brush or cap overnight, nozzles soaking in clean water and lines cooled right up to the tap are the basics. The cold room and any glycol chiller should run all night even when the bar is closed, so the beer in the system stays cold until morning. Switching them off saves a little power. Leaving them on saves pouring away beer every morning and keeps the first customer from tasting yesterday.

Your palate is part of it too

Not every off first pint is the bar's fault. Your mouth changes through the day. The first beer often follows a meal, coffee, toothpaste or nothing at all. Mint and coffee in particular can make the next drink taste thin or bitter. Our guide to why the first and last sip taste different explains how the palate shifts within one glass.

A sip of water before your first beer helps. If the second beer from the same tap tastes clearly better than the first, the line was probably the problem. If both taste the same, it may have been you.

What a good bar does at opening

• Removes the overnight plugs and refits soaked, clean nozzles.
• Pours off the beer sitting in any uncooled part of the line, often 100 to 200 ml a tap.
• Pours and tastes a small sample from each tap before the first customer.
• Checks the beer temperature in the glass.

This takes a few minutes and costs a little beer. It saves far more in sent back pints and customers who never return.

What to say if your first pint is off

Be polite and specific. "This tastes a bit warm and flat, could you pour me another?" or "There's a buttery note, is the line due a clean?" gives the bartender something to act on. A good bar will replace the beer and pour off the line. A great one will thank you.

Your first step: next time you arrive as a bar opens, order a small taster from the tap before your full pint. If it tastes off, mention it and let them pour a fresh one. You will learn a lot about the bar from the reply.

Common questions

Why does the first pint of the day taste different?

It has sat in the lines and tap overnight, often warming and picking up flavours from the tap or a dirty line.

Should bars pour away the first beer of the day?

Many good bars pour off the beer in any uncooled part of the line, often 100 to 200 ml a tap, then taste each tap before opening.

What does a buttery taste in draught beer mean?

Often diacetyl from bacteria in a line that needs cleaning. If later pints taste cleaner, the line is the likely cause.