I tested water out of the tap today and got 12ppm
Tested it out of my filter and got 0
I have this setup:
http://www.jlaquatics.com/phpstore/s...ct_ID=ro-aptwp
It changes colour when it is time to change it. Or just keep testing it with your TDS meter to see if he quality has changed. A friend in North Van has a 75 gallon right now and with weekly water changes he still only has to replace it every 8-10 months.
Our water quality is fairly good in the lower mainland (actually awesome compared to other places). Simply because of our climate, protection, and proximity to the resevoirs.
How big is your tank You may only need this if you don't want to take many trips to the grocery store.