Is this what you guys mean to filter my water?

http://www.amazon.com/gp/product/B002YFX3D0/ref=olp_product_details?ie=UTF8&me=&seller=

is that it? Like should I be filtering all my water through that before giving to plants?

this will help but only does 18 cups at best. I would drop a few more bucks and get an inline RO unit. also (i read it quickly) this unit will only remove some crud. better than nothing though

I hear the nutrients in tap water are supposed to be good for the plants, but I have not tried it yet

http://www.amazon.com/Reverse-Osmosis-Storage-Removes-Fluoride/dp/B002LHDL7E/ref=sr_1_4?s=home-garden&ie=UTF8&qid=1313521094&sr=1-4

this is more like what you need.

tap water can contain micro nutrients that are benefitial to plant, but more often than not tap water contains harmful amounts of salts, chlorine, flouride, sulfer, amoung others.
i belive tap water with a ppm of less than 150 is suitable to grow cannabis but i would recommend 40 or below.
when i grew out of an apartment our tap water was 500 ppm, after reverse osmosis it went down to 7-18 ppm.
just know that filtered water requires a complete nutrient solution to feed plants, as it contains little or no minerals.

I use tap water, leave the jug out for the chlorine to evaporate, then i pour it into 5 gallon buckets with a pump from a fish tank to keep the water good and from forming any more bacterias.

i use filtered water but from what i here as long as u let tap water sit fro something like48hrs its fine to use

Depending on your stats of the tap water at your plants location, it should be fine... run a TDS meter on the water right from the tap... really anything under 100 should be completely safe. I have RO unit here and dont use full RO water... I run all my tap through a pre filter and a carbon filter, leave everything else be. Most tap water PH is 6-7... a touch of carbon filter and that PH is now 5.5-6.5 normally... full ro'd water PH normally drops to about 5 sometimes lower...

Also tap water has lots of items beneficialto your plants and honestly typical tap water has nothing that will harm your plants. Majority of the US no longer uses Chlorine in tap water but Chloramine. Chloramine does not break break down even if you left it out for a week.