One pump operating with discharge pressure of 5ksc, and its discharge is connected to a tank(tank is located H meter above the pump). A PG is installed near the tank.so what is pressure shown by PG and WHY?

Use Bernoulli's principle, which for an incompressible fluid like water is:


\frac {v^2} 2 + gz + \frac p {\rho}\ = \ Constant


Consider what happens at the point where the water exits the pump (call it point 1) and the point where the water exits the pipe into the tank (call that point 2). From Bernoulli you know that:


\frac {v_1^2} 2 + gz_1 + \frac {p_1} {\rho} \ = \ \frac {v_2^2} 2 + gz_2 + \frac {p_2} {\rho}


You know that the velocity of the water is the same at both places, and you know that the height z of the tank is H meters above the pump. So this becomes:


\frac {p_1} {\rho}\ = gH + \frac {p_2} {\rho}


Solve for p_2