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-   -   Hydrometers, distilled water, and calibration (http://www.homebrewtalk.com/f13/hydrometers-distilled-water-calibration-98703/)

maltMonkey 01-19-2009 06:46 PM

Hydrometers, distilled water, and calibration
 
Quick question, as I have not seen this info posted anywhere before:

For a correctly calibrated hydrometer to register 1.000, you must use distilled water ( I get 1.004 in my tap water). But since I BREW with tap water, shouldn't I be subtracting .004 from the readings in my beer?

I assume that all those minerals still make it through the mash, sparge and boil into the fermenter, right?

remilard 01-19-2009 07:05 PM

That is some pretty dense tap water. If you measure distilled water and your tap water at identical temperatures do you really observe a .004 difference?

homebrewer_99 01-19-2009 07:12 PM

Are they both at 60F?

hopsalot 01-19-2009 07:18 PM

Quote:

Originally Posted by remilard (Post 1075084)
That is some pretty dense tap water. If you measure distilled water and your tap water at identical temperatures do you really observe a .004 difference?

temp is important. my ground/tap water floats at 1.000. It would seem to me that distilled would be lighter, not sure though

maltMonkey 01-19-2009 07:23 PM

yes, the tap water was at 60 - reading measured from the bottom of the meniscus.

homebrewer_99 01-19-2009 07:59 PM

Welll, if it's off by .004 then that's your correction factor.

I don't know what else to tell you.

maltMonkey 01-19-2009 08:06 PM

Maybe I'm not being clear: the hydrometer is CORRECT if you use distilled water (which is how every hydrometer calibration tutorial tells you to do it). So it reads correctly at 1.000 using distilled water, but there are minerals and such in my tap water which cause a .004 higher reading.

My question is should I adjust for this when brewing with the same tap water, making the assumption that all these minerals make it through the final boil into the fermenter, thus causing a .004 higher reading in the finished product?

remilard 01-19-2009 08:47 PM

Most tap water has an SG of 1.000. Your water has 15% as much difference from pure water as does sea water. It is hard to imagine that would be drinkable.

maltMonkey 01-19-2009 09:03 PM

I'll double check them again tonight against some distilled water. They read 1.000 when I last checked them with distilled water several months ago, but just checked the tap water last night....

maltMonkey 01-19-2009 10:48 PM

Well, disregard this post....

Just recalibrated in distilled water and both are reading at 1.003, while they read 1.004 in tap water. I didn't think that hydrometers could shift out of whack, but perhaps I screwed up when I checked them in distilled water months ago :confused:

They also read 1.085 in 1.083 wort.....So rather than doing some tricky math every time I'm just going to take the average and subtract .003 from all measurements.

Sorry for wasting everybody's time.


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