I process water in a soft water area (Cornwall - 95ppm) so I do not have to worry quite as much as some WC's. I like to flush the membrane for about 5 minutes before each tank fill (2500 litres). About once a month (when I remember!) I then also flush for about 30 minutes.
I have had my current HF4 membrane for about 2.5 years and it is still producing water at about 002ppm - input pressure of about 100psi.
that last part makes me green with envy my water is very hard but to be fair my membrane has lasted years flushing as I do
Dave I would be interested on the figures of what your doing
Cost over saving will be interesting.
I don't use a water softener for his reason against what some suppliers say ( not you Alex )