Wrote this before I realised it had already been covered,“Cask breather or Aspirator ” but never mind. The debate about using co2 as a top pressure on cask ale seems to polarize most drinkers. From a technical point of view and speaking as a technician of 40 years standing, I see the advantage of supplying a maximum top pressure of say 2 psi, to casks. It will prolong the life of a cask beer, keeping it in better condition than if a cask is just left open to atmosphere. Having installed many aspirated systems as they are called, I cannot think of one instance where there was a negative affect.
The affect of using a co2 top pressure is to exclude air born bacteria from the cask and not as some people may think to push the beer from the cask. Aspirators do not turn cask beer into keg beer.
However there is another valid argument used by lots of real ale buffs which runs along the lines of keeping things the traditional way and not introducing any system that is not traditional. This may from an aesthetic point of view be valid but practically speaking how many cask beer drinkers would know if a cask beer was using a co2 top pressure or not. My personal feeling is that there is no disernable change in the taste or character of cask beers using aspirators.
Using aspirators is viewed as sacrilege by some and unnecessary, but I do not agree, I think they are an integral and perfectly valid part of cask beer dispense and not just a gimmick to save the landlord money. I am unaware as to the CAMRA view on aspirators and would welcome there opinion on this contentious issue.
If after reading this article you are persuaded to give it a go, you will find the cost of installing this equipment is very reasonable and your local brewer may even pay to have it installed.