There is no standard amount of time for flushing membrane as it varies according to water quality, pressure and temperature. In some cases 4 hours may be a little over the top, but the biggest cause of membrane failure is them becoming clogged or blocked.
Flushing dramatically improves their life and performance.
We are the only company to guarantee our membranes (any other company would just insist on selling you a new one), so obviously we want to protect them, but this is for your benefit too.
I’m sure you’ll agree that it’s not in your best interest to just continually degrade your performance, and slow down your production, until you’ve flogged your membrane to death… and then claim on our warranty.