r/o top off

Can anyone piont me to how to use r/o as auto top off with out a resevior and pump?

 

It is not advised since the float valve can and will fail flooding your tank with fresh water and killing everything.
It is always better to fill a ATO reservoir with RO/DI and pull from that so you have a lesser quantity that could possible flood or dilute your system. It is also better since float valves cycle on and off frequently and cause a RO membrane to have what is called TDS creep meaning you get a spurt of high TDS water every time the level in the tank drops a hair and it soon eats DI resin and causes membarne failure.

 

cool thank you.