Calibrating Hydrometer in tap water?

Quick question to you all. After realizing that my cider should not come out to 1.010 and my Saison should not come out to 1.020, I decided to do a quick calibration of my hydrometer. I only had tap water, no distilled water, and at 64 degrees, it came out to 1.005. Will using tap water vs distilled water make enough of a difference or should I be content to add .005 to all my readings. Thanks.

mkorpal said:

Quick question to you all. After realizing that my cider should not come out to 1.010 and my Saison should not come out to 1.020, I decided to do a quick calibration of my hydrometer. I only had tap water, no distilled water, and at 64 degrees, it came out to 1.005. Will using tap water vs distilled water make enough of a difference or should I be content to add .005 to all my readings. Thanks.

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I guess it depends on what's in your tap water! I'd try to get a small amount of distilled water and testing it again, before trusting it.

I'd expect you won't see much of a difference, even if you have hard water, since most minerals are measured in ppm (parts per million), so there isn't much there.
If you're getting the water from an aerated faucet, you might try letting the water sit overnight to let the air come out of solution, but it probably won't make much difference.

If you'd like to do a multipoint calibration, it's pretty easy to make sugar solutions and use the Brix scale. Kinda fun for geeks, but not really needed.
I've also done my own temperature correction chart, and that is clearly overkill

Thanks. I may pick up some distilled water when I'm at the store. But I'm not too terrible anal about being exact, so I may not worry too much about it.

I have pretty hard tap water, and my hydro reads 1.000.