How do I calculate the water pressure in a water tank?

Question

I want to put an access on the side of a water tank at low level. The tank dimensions are 3000x3000x2000mm high and holds drinking water (gravity fed) I am bulding the access, but want to test it before installing. Help please!

Answer 1

The pressure head is given by

P = h * rho * g

P = Pressure

h = height of liquid column (2000 mm = 2m)

rho = Density of water (1000 kg/m^3)

g = Acceleration due to gravity (9.81 m/s^2)

P = 2 * 1000 * 9.81 = 19620 Pascal = 19.620 KPa

I Pascal = 1.02 * 1.02*10^-5 kg/cm^2

Therefore pressure at the lowest point is 0.200124 kg/cm^2.

Alternate method: 1 m Water = approximately 0.102 kg/cm^2

Therefore 2 m = 0.204 kg/cm^2 = approximately above answer

To get the pressure in psi (pounds square inch): 0.204 kg/cm^2 / 0.07 = 2.89 psi (Since 1 psi = approx 0.07 kg/cm^2)

2 m water = 0.204 kg/cm^2 = 2.89 psi

Answer 2

The water pressure depends solely on the height of the water column. In this case, that is 2000 mm = 2 m

2 m = 6.56 ft. Since water weighs 62.4 lb/cubic foot, the 6.56 ft will exert a pressure of 2.84 psi. Not very much.

Answer 3

If the tank was raised 2m above the ground, would the pressure then double?

Norrie. Thanks, I'm thinking of putting in a tank to increase my mains pressure at the tap; now I know it doesn't have to be big, just high!

Answer 4

Water pressure at a depth h, is simply p*g*h. p is the density of the water (usually 1000 kg/m^3), g is the gravitational acceleration (9.8 m/s^2 or 32.2 ft/s^2) and h is the depth you want to know the water pressure at (probably the deepest part of the tank since the pressure is greatest there). Make sure all your units are consistent.

Answer 5

2,000mm = 200cm height.

1cm³ = 1mL = 1g of water.

1cm³ = 1cm x 1cm x 1cm high = 1mL = 1gm of water.

Area of base of 1cm³ = 1cm².

Height of tank = 200cm.

200cm = 200mL = 200g.

Pressure on tank base = 200g acting on 1cm². = 200g/cm².

In psi this will be...

200cm / 2.5cm/inch = 80in / 12in/ft = 6.67ft.

1ft of water exerts a pressure of 0.433psi.

6.67ft x 0.433psi/ft  = 2.9psi at the tank bottom.

AsiaAdvice: If the tank was 2m above ground level with a bottom outlet to the ground level then, yes, the pressure would double because there would be 2 more meters of water exerting pressure.