Lique Marco Ferrante said, ...

Lique Marco Ferrante said, water hammer which usually is not a problem when you have velocities as low as 1 m/s can become a major problem. On the other hand, headloss is proportional to the square of the velocity an so if you jump from 1 m/s to for example 4 m/s the headloss will be 16 times bigger and this can be another major problem (in gravity flow probably you will not have enough head to supply the flow you want or you will not have the necessary pressure for the flow you want; in pumping systems you will need much more energy to overcome such a big headloss that probably it will not be cost effective). Just do the maths!