I got some new taps for my kitchen yesterday. The boring technical specitications on that bit of paper marked ‘important – please read’ said ‘do not exceed a pressure of 800 kpa’. Now, leaving aside the fact that it should be ‘kPa’ not ‘kpa’, that means 800 kilopascals. A pascal is the pressure caused by 1 newton of force applied to an area of 1 metre squared. (1 newton of force is about the gravitational force on 100 g of mass). What 800 kPa translates to is the same pressure that you would get under a head of water eighty metres high. That’s a fairly sizeable water pressure. But some places will could exceed that, for example if they were fed directly from a resevoir more than 80 metres higher than their house.
Incidently, the air pressure in the beam tubes of the LHC is a mere hundreth of a millionth (ten to the power of minus eight) of a pascal. That’s the lowest vacuum that’s ever been created, or, putting it another way, a tenth of the air pressure on the moon. That’s low.