The first thing is to be specific as to exactly what it is you’re complaining about. If the beer is obviously cloudy or vinegary, then you should have a cast-iron case, although opinions will vary on what degree of haziness is acceptable. Personally, unless it’s declared as a beer that is intentionally hazy, I’m pretty dogmatic on the issue, and will reject anything with more than a slight cast. But, of course, if it is a deliberately hazy beer, how do you or the bar staff know how much haze is too much?
However, there are other faults that are not so clear-cut, for example being served far too warm, lacking in condition, having a noticeable off-flavour such as diacetyl, or simply being generally tired and end-of-barrel-ish. If you’re in a pub where you’re a regular and are known to the licensee and bar staff, such a complaint might be taken seriously, but in a strange pub you could well feel that you are chancing your arm.
It’s also important to clear about your objective when making a complaint. Obviously the best solution is to be given an acceptable replacement, either the same beer which has been pulled through, or a new cask tapped, or a suitable alternative. Failing that, the aim should be to be given a refund, which you may well prefer if it’s the only cask beer on sale and you don’t fancy a Carling as a replacement. Or, in some cases, just venting your spleen will leave you with a sense of moral satisfaction.
The last two outcomes, though, imply that you’ll be bringing your visit to an end. If you’re in the middle of a pub crawl, or there’s an alternative pub nearby, or you’ve just popped in for a swift pint, that might be entirely acceptable. But in other situations, for example having a meal or social evening with a group, or watching a football match or live music performance, you might not want to do that, and thus be reluctant to create a fuss. You’ll just quietly leave the sub-standard pint, and put up with Guinness or Diet Coke for the rest of the proceedings. The point has also been made in the past by Tandleman that you’re going out for a pleasant social evening, and creating a confrontational situation may end up leaving a sour taste in the mouth even if you gain a moral victory.
I’d say in general that attitudes to changing sub-standard beer have improved over the years, although it may simply be that as a more mature chap I command more respect than a pimply youth. The days of “everyone else is drinking it” or “real ale’s meant to look like soup/taste like vinegar” are largely a thing of the past. One of the worst responses I recall was “but you’ve drunk some of it!” Well, if I hadn’t drunk any, how would I know it was foul?
However, as Martin and his friends found out, that kind of quibbling hasn’t entirely disappeared. In that case, although they had spent £60 in the pub, they would now think twice about going back and he has disseminated his experience over the Internet. Given the amount of goodwill at risk, compared with the gross profit on a pint, it’s hard to see why pubs continue to argue the toss about changing beer if customers present a reasonable case. After all, I don’t think anyone beyond a handful of troublemakers deliberately sets out to wind pubs up by returning perfectly good pints.
To their credit, Wetherspoon’s seem to have adopted a no-quibble policy when it comes to exchanging cask beer. Bar staff who are not beer experts will be in no position to decide whether or not a complaint is valid, and they must recognise how much goodwill they stand to lose. If any customer established a reputation as a “vexatious complainant”, I’m sure it would be brought to management’s attention.
No doubt someone will point out that that, if you stick to mass-market lagers and smooth beers, you won’t have any of this problem with variability. However, the point about cask beer is that, when it’s good, it’s much superior to kegs and lagers, and the occasional duff pint is a price worth paying for that. If you stick to pubs in the Good Beer Guide, or ones with a decent reputation locally, you’re unlikely to have much problem. The only returnable pints I’ve had in recent months have been when drinking off-grid in pubs that I happened to like the look of, but came with no recommendation. And keg beers, especially small-batch “craft” ones, are by no means immune from faults either.
But, if you go into a food- or sports-oriented pub with a solitary Doom Bar handpump at the end of a long line of kegs, it’s entirely understandable if you decide to give it a swerve. And, at least once, we’ve all been there with that pint of slightly warm, slightly flat, slightly stale, slightly hazy beer, where no one fault really makes a convincing case for taking it back, but we conclude the best solution is just to leave it unfinished on the table...
Edit: I’ve added a poll on taking beer back in the sidebar, which mobile users won’t see.