My tests confirm that Mountain Spring water and bottled seltzer may not be any cleaner than tap water. They also reveal that Brita-filtered water hardly reduces the amount of dissolved solids in tap water.
SURPRISING WATER TEST
As most of us know, tap water is contaminated with various materials ranging from pipe rust to harmful additives such as chlorine and flouride to extermely hazardous chemicals. Publicized tests of bottled water have raised questions about its purity as well. In some cases water labeled as "Spring Water" has been shown to actually be bottled tap water!
I live in New Jersey where the water is known to be of low quality. New York City water is considered to be much better. About two decades ago we started using water filtration devices--carbon faucet filters. A few years later we purchased a countertop reverse osmosis filter. For about a year now we've been using an under-the-counter 5 stage reverse osmosis system.
For years I have tried to evaluate the amount of "dissolved solids" in the water, which is a rough indicator of its purity. Less dissolved solids tends to indicate cleaner water. You don't know cleaner of what, but whatever things are in the tap water considering the gunk you find in the little faucet screen, can't be that good for you. The guy who sold me the countertop reverse osmosis filter had a little Total Dissolved Solids Meter ("TDS Meter") which shows the amount of dissolved solids in Parts Per Million or "PPM". I tried to gauge the purity using a multitester on the resistance function--the lower the resistance of the water, the more dissolved solids it tends to have. (If you pour organics or salt, etc. into water it will have a lower resistance to electricity, while super-pure water will have a very high resistance). It didn't appear reliable because the temperature of the water also varies the resistance. Then I found that if I used the ammeter function with an external battery I got much more consistent results--showing the conductivity in milliamps. I didn't get PPM numbers, but could do comparative measurements.
Well, when I got the new under-counter system I decided it was time to get a professional TDS meter. I got a Hanna HI98311 TDS meter for $70. These meters start at about $20 on eBay so this meter is of semi-pro quality. It has automatic temperature calibration which compensates for different sample temperatures, and also shows you what the temperature is, and indicates when the reading is stable.
To make a long story short, when I was in New York at my aunt's apartment for Passover, I brought the meter along with some of my reverse-osmosis water, and did some water-quality testing. I was sort of surprised by the results!
Differences of a few PPM are probably not significant. What's shocking is the White Rose Seltzer water. At about 200 PPM it's similar to NJ tap water. There was a difference between two bottles as well, so who knows how dirty it can get. The Brita appears to help the NY tap water a bit, but maybe not--the difference is very small 38 vs. 42. The Wissahickon Mountain Spring water is similar to the Brita and NY Tap water at 38 PPM. Coincidentally I read somewhere that per national standards water that is below 40 PPM is considered safe to drink. The best is the steam distilled water--I was dissapointed that I couldn't get a measurement at all. However this type of water usually comes in a plastic gallon which tends to leech some plastic chemicals into the water, hence the plastic taste.
Clearly, the reverse osmosis water is a pretty good choice and the cost at a few pennies a gallon when you consider filter replacement cost, is lower than bottled water, or the Brita filter which doesn't seem to do too much for the dissolved solids anyway. I suppose that's why reverse osmosis water filters have become very popular and are available on eBay and elsewhere for around $200. Replacement filters are cheap at a few dollars each. Many of the units have a transparent pre-filter, and within about 3 months my pearly-white filter turned brown. I can only be glad that the "brown stuff" didn't end up in my body!