Water SG Question

[GHBWNY]

I have used both straight tap water and water from our under-sink Aquasana filter to brew with. While I know calibration of a hydro is supposed to be done with distilled water, just for kicks, I took a sample of each at identical temps (65F) anyway. The tap water came in at 1.002; the filtered at 1.000. Is there that much "material" in our tap water to make that much of a difference? Or is my hydro actually reading incorrectly?

 

[flars]

I did the same type of calibration test with tap water, from our well, and distilled water. At 60°F, calibration temperature for this hydrometer, the distilled reading was 1.000. The tap water reading was 1.002. Then I noticed the tap water sample was aerated and air bubbles were clinging to the hydrometer. Spinning the hydrometer released the bubbles, the SG reading settled to 1.000.

 

[GHBWNY]

I did the same type of calibration test with tap water, from our well, and distilled water. At 60°F, calibration temperature for this hydrometer, the distilled reading was 1.000. The tap water reading was 1.002. Then I noticed the tap water sample was aerated and air bubbles were clinging to the hydrometer. Spinning the hydrometer released the bubbles, the SG reading settled to 1.000.

Have you brewed with both? Noticed any difference in the brewing procedure or taste?

I normally use filtered water in most of my brews, so I'm going to presume the gravity readings for those brews is more accurate. I brewed yesterday with straight tap water, just to see if there is any taste difference, and my OG came in 6 pts lower than the low end of the recommended range for the recipe, which is a theoretical 8 pts lower using the filtered water.

 

[flars]

I have only brewed with our well water. The different styles of beer I brew always taste great, so no experimentation with distilled water.
On the home farm, the well water was heavy to iron, we did brew lighter styles of beer with distilled water.