The pressure increase from the free surface can be calculated with the formula for the weight of the water column divided by the cross sectional area, that is d*g*h, where

d = 1 000 kg/m^3 is water density,

g = 9.8 m/s^2 is gravity and

h = 15 m is the depth.

Then we get 147000 Pa = 147 kPa = 1.47 bar.