Learn something new everyday. So each grain = 16.9 ppm (507ppm / 30 grains)
17.9 ppm equates to 33 Microsiemens or 1 dH.

7.72 grains * 16.9 = 130.468 ppm = (130.468/17.9) = 7.288 dH.

I'd say that's fairly soft water.

Buzz



Sorta, kinda.

The 16.9 is a bit suspect, the city may have rounded off the numbers.
I have seen the number 17.1 used for this conversion.

The microsiemens is an approximation, it is measuring conductivity,
not the particular chemicals causing the conductivity.

Hardness used no mean how much calcium and magnesium was in the water.
If you added table salt the conductivity, the microsiemens, would go
u-p but the Ca/Mg hardness would stay the same.

Hardness of 130 ppm is considered hard by the water industry.

http://wilkes.edu/~eqc/hard1.htm

It would be very soft compared to what I have for tap water.
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- Charles
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-does not play well with others