I plan to invest in a reverse osmosis filtration system soon myself. Currently I am just using well water though which seems to be perfectly fine, less shit than is in the public water system.
My buddies who live in town go fill their jugs of water though rather than using tap water. If you have one close, it is rather inexpensive to fill up your jugs.
Here's to a real answer from someone who has done their homework... kudos.A little note about using tap water: the water sources for the Valley vary over the course of a year. Sometimes it's canal water, sometimes it's from wells- and the total dissolved solids (TDS) varies throughout the year.
So- it may work well at some point, and then later you'll find out that it's not working quite so well.
However, much of the total dissolved salts found in the tap water here consists of calcium and magnesium- which some people pay more for in the form of CalMag at the hydro store. Other components (sulfate, iron, carbonate) are also used by plants. The chloride isn't needed by plants, but won't harm them except in very high concentrations.
While the tap water here can be very "hard," it's not necessarily detrimental to plants unless one allows the salts to build up for too long. The pros will go with an RO unit, of course, since the extra money is worth it for labor- and energy-intensive crops.
Yeah great answer. I still use RO and will until I drink the tap water here myself. RO gives me a clean slate that I can mix up my own nutrient solutions with the proper ratios. That's great that tap water has so much Cal mag in it but I don't like that much and I want to know exactly how much is available to my plants. If you know what you are doing, then the more control you have over your environment the better. If you are not really sure what you are doing then it wont matter.