Water pressure depends on the 'head' of water - the height of the top of the level at which it is used. This is because of the pressure exerted by the volume of water above the side of a plastic bottle. Cover the holes with sticky tape and fill the bottle with water. Remember to place a bowl on the floor to catch the water before quickly removing the bits of tape. The jet of water where the pressure is greatest (at the bottom of the bottle) squirts out farther than water from near the top