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Re: Measuring KH

> Date: Fri, 16 Feb 2001 12:00:29 -0600
> From: Trey_O_Zagst at cargill_com
> Subject: Measuring KH
>      I have been using an electronic "pen" that I believe measures total 
> dissolved solids in the water.  It gives a reading in ppm.  I use it to help me 
> figure how much tap water to mix with my ro/di water.  I have been shooting for 
> a measurement of around 120-180ppm.  I have just been assuming that this should 
> give me around 6-9 KH and DH.  Am I making a dangerous assumption?  It is just 
> so easy to dip the pen in the water vs. doing the hardness tests I have used in 
> the past.

It's a perfectly valid thing to do, Trey, if your water doesn't vary much,
and you have an initial calibration from your water department or a KH kit
that gives the percentage of the total dissolved stuff as carbonates.

For example, I know that my total hardness is roughly 2/3 of my total tds,
so I assume it is about 200 g/l when the tds meter reads 300 ppm. Of that,
about 2/3 is carbonates, so my dKH is likely about 9 or so. [Assuming my
mental arithmatic is not wildly in error.]

The hooker in most water systems seems to be the amount of sodium chloride
in the water. In some places, it varies wildly with rainfall and even the
tides. There, the tds meter tells you almost nothing about KH. Most places
are more stable, and it can be great.

I'd suggest that a KH titration measurement, once in a while, will make your
quick and easy tds measurements most meaningful, or at least give you
confidence in them.


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

              Politicians and diapers have one thing in common. 
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