As the air temperature starts to increase, the pressure in barrels will start to increase as well and even barrels fitted with a pressure vent system may well start to leak from around the tap. Whilst the pressure vent should release the extra pressure, if the tap provides an easier escape route, the CO2 will try and vent from there and will invariably take quite a lot of beer with it. If your tap is leaking more than usual or the barrel is showing any signs of bulging, you should take steps to immediately reduce the pressure.

The best way to do this is obviously to pour a few pints off, but if this isn't possible, then some of the pressure should be released by means of the safety vent or the pressure release rubber on the valve.