Another question about my municipal water

Hi,
I have been using the yearly report produced by my water company plus GH/KH tests to catch some of the seasonal variations.

In the reports produced for the last three years, Mg isn't listed and the Ca harness corresponds to the total harness. I assumed the water has no Mg.

Today I got a Ca titration kit and tested along with GH to discover only about 80% of the total harness is Ca harness, which kind of makes sense.

So, has my water supplier just taken a shortcut and listed Ca based on harness measurements? Note in the yearly report, Ca and harness were sampled once only. They haven't answered my queries.

Should I trust my measurement? Is zero Mg even possible?

The reason I am asking is that I have been using MgSO4 to boost Sulphate without adding Ca. That was assuming I had little to no Mg, but my test shows around 16ppm so my additions are taking me slightly above the recommended limits.

I cannot say if any of my beers have teased bad because of excessive Mg, but then again, what do I know about beer.

Thanks

To begin we say that calcium and magnesium contribute hardness (as opposed to softness - the descriptor for mineral free or low mineral water). A harness is a thing that goes on a horse.

It is in fact quite probable that your water contains some magnesium hardness. The fact that the utility does not report it suggests that it is indeed minor but note that drop count tests are pretty innacurate and this may be contributing to the apparently high magnesium content (20 of TH).

ajdelange said:

To begin we say that calcium and magnesium contribute hardness (as opposed to softness - the descriptor for mineral free or low mineral water). A harness is a thing that goes on a horse..

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I wish I cold pin it to auto-correct, but no, it is just me.
Not long ago, I learnt the hard way that wether is a castrated ram, and not an expression of doubt. Made my presentation slightly less credible, unfortunately.

ajdelange said:

It is in fact quite probable that your water contains some magnesium hardness. The fact that the utility does not report it suggests that it is indeed minor but note that drop count tests are pretty inaccurate and this may be contributing to the apparently high magnesium content (20 of TH).

Click to expand...

When brewers send their water to a laboratory for analysis, I guess the lab uses more reliable reagent and good methods for measuring it (rather than just counting drops)?

I have done my GH (API test) measurements doubling the amount of water tested, hoping I would half the error. Assuming the reagent is good, should I just further increase the amount of water to be tested? I can do the same with the Ca test, increasing the amount of water to be tested.

What is the pragmatic quasi scientific approach here? Or should I just assume Mg and Ca to be somewhere in between the water report and the measurement?

p_p said:

When brewers send their water to a laboratory for analysis, I guess the lab uses more reliable reagent and good methods for measuring it (rather than just counting drops)?

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The hardness tests (with EDTA and Eriochrome black) are sort of dated. Most modern labs would determine the metals by AAS or ICP. Thus if one looks at a Ward Labs test, for example, the total hardness doesn't quite agree with the hardnesses calculated from the Mg and Ca reported values. Labs doing an EDTA titration would use a buret of some sort to dispense the reagent. This will be more accurate that drop count testing.

p_p said:

I have done my GH (API test) measurements doubling the amount of water tested, hoping I would half the error. Assuming the reagent is good, should I just further increase the amount of water to be tested? I can do the same with the Ca test, increasing the amount of water to be tested.

Click to expand...

That's the approach I would take.

ajdelange said:

That's the approach I would take.

Click to expand...

Thanks for that AJ.

One more question which I posted some time ago but did not get a reply.

What kind of performance change should I expect from my API & Salifert reagent? (I have read data from API indicating Ca & GH last three years and KH 4 years) but nothing is said about decay during this period.

The kit is stored at ambient temperature and I try to handle such to avoid evaporation.

Hard to answer. The approach most labs take is to obtain (or prepare) standard solutions and check against them periodically. Hach and others sell solutions for this purpose.