RODI in, TDS out! How long will it take?

Now that I'm using RODI water, I was curious how many 10% water changes I need to make before I totally replace the old water with the new? Are there any forumlas out there that calculate this?

 

Lots and Lots.

But don't worry about trying to replace all your old water, just use the new better water from now on (unless you have a major problem, then you want to do larger than 10% changes to change out the water).

With 10% changes, first change, you have 90% old water. Second change you have 81% third change 72.9 fourth 65.91.... Each 10 changes less and less of the old water and more and more of the new water...

Kim