



Discussion
How much does water pressure increase per vertical foot?
Fresh water: 0.43 psi per foot Sea water: 0.44 psi per foot.
So, for each additional 10 feet of depth, figure about 4.3 to 4.4 psi increase in pressure. You can calculate this yourself by using the fact that fresh water weighs about 62.4 pounds per cubic foot (pcf) and sea water weighs about 64 pcf. Divide those numbers by 144 (the "footprint" of one cubic foot, 12 x 12) and there you go. It's interesting to note that this pressure is independent of volume or expanse. i.e. the water pressure behind a fresh water dam at 100 feet deep is about 43.3 psi regardless of whether the dam's reservoir is 25 miles long or 10 feet long. Depth and density are the only relevant parameters needed to determine pressure. Dive pressure, however, would be the water pressure of 43.3 plus the air pressure above the water. So the net pressure on your ears & body would be 43.3 plus 14.7 (one atmosphere)totalling 58 psi,or about 4 atmosphers. That's four times our normal experience. Worthy of careful consideration. 



singapore
Joined Jan 2005
199 Posts

Move somewhere outside the states and you will find that for every 10M the water causes pressure to increase by 1 bar, so for one metre it increases 0.1Bar, and 10cm = .01Bar. 1 Bar is roughly equal to 1 atmos, so at 1metre you are under 1.1 atmospheres. A much simpler calculation. Alternately the US could ditch the imperial system which even the imperials have dropped




I SCUBA dive and (1) atmospheric pressure equals 33 feet of water depth.Or 14.7pounds per sq.foot...RTR
see here...http://wiki.answers.com/Q/How_much_d..._vertical_foot 


Joined Nov 2009
1 Posts

rate of pressure increase does not stay the same per depth
The atmospheric pressure at the surface is 14.7 PSI or around 100 kPa. A comparable water pressure occurs at a depth of only 10 m (33 ft.) (9.8 m (32 ft) for sea water.) Thus, at about 10 m below the surface the water exerts twice the pressure (2 atmospheres or 200 kPa) on the body as air at surface level.
For solid objects like our bones and muscles, this added pressure is not much of a problem; but it is a problem for any airfilled spaces like the mouth, ears, paranasal sinuses and lungs. This is because the air in those spaces reduces in volume when under pressure and so does not provide those spaces with support from the higher outside pressure. Even at a depth of 8 feet (2.5 m) underwater, an inability to equalize air pressure in the middle ear with outside water pressure can cause pain, and the tympanic membrane can rupture at depths under 10 ft (3 m). The danger of pressure damage is greatest in shallow water because the rate of pressure change is greatest at the surface of the water. For example the pressure increase between the surface and 10 m (33 ft) is 100% (100 kPa to 200 kPa), but the pressure increase from 30 m (100 ft) to 40 m (130 ft) is only 25% (400 kPa to 500 kPa).[/B] 
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