Just wondering how precise are ward labs results on tap water ? 21$ for a houshold mineral test is damn cheap compared to other companies in Canada. I was quoted 150$ for a similar test here. Is ward labs really testing each minerals/ions individually ?
Ward labs precision
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Weezy
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Analytical labs use industry standard test methodologies and typically have certification credentials for many if not all tests they run. They also use commercial equipment suitable for said tests.
I'd be less worried about their test results being inaccurate than I would about my water profile varying season to season.
I'd be less worried about their test results being inaccurate than I would about my water profile varying season to season.
Weezy
Well-Known Member
Correct.
Brutus Brewer
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before i sent my water to Ward I talked to a lab here in town. They told me Ward probably has a machine that will test all parameters at once. The local place could do it but each item would be tested individually and priced individually
Ward Labs tells you at the top of each report how accurate the test results are. This is in the Anion/Cation balance numbers. If the report is perfectly accurate then those two numbers will be exactly the same. If they differ by 0.5 then some error or errors amounting to half a milliequivalent per liter are responsible. This could be an error in measurement, calculation, failure to test for some ion which is present and, in most cases, a combination of the above. Note that 0.1 mEq/L hardness error amounts to 2.0 mg/K calcium, 1.2 mg/L magnesium, 5.0 ppm as CaCO3 alkalinity, 2.3 mg/L sodium, 4.6 mg/L sulfate and 3.5 mg/L chloride. If cations differ from anions by more than 0.5 the test is inaccurate and you should contact Ward Labs, inform them of this and request that they re do the test. In most cases they seem willing to do so.
The place where Ward Labs does fall down a bit (and part of the reason then don't get smaller cation/anion imbalances) is that they don't fully understand the relationship between alkalinity, carbonate and bicarbonate. They were using a 'standard procedure' dated 1934 (or thereabouts) from the Department of Agriculture which called, as so many alkalinity procedures do, for measurement of P and M alkalinity but were measuring P at pH 8 when it should be done at 8.3. This screwed up carbonate concentration whenever pH > 8. I pointed this out to them and they have started using 8.3 but are still not calculating carbonate correctly though bicarbonate numbers seem to be better now (I did indicate to them where they could get the correct procedures for calculating carbonate and bicarbonate but never heard back from them). As it is rare that they test water at pH > 8 this is seldom a problem.
Another place you may notice a discrepancy is between the reported levels of calcium and magnesium and the total hardness. They probably measure hardness with an automated titrator and probably measure the individual metals (including sodium and iron) with ICP (at least they advertise that they have ICP capability on their web site). Alkalinity would also be measured by automated titration. Sulfate is a tough one and probably responsible for a good part of the error in any report. It is usually done by precipitating barium sulfate and then determining that gravimetrically or by looking at the turbidity of the sample after barium chloride has been added. If the chemistry is calibrated frequently enough it is possible to get a pretty good result but I have no idea how they actually implement this test (or any of their tests). I was quite surprised that they were using the ancient DOA protocol for alkalinity but then they mostly serve the agriculture industry and the test is the same as the AWWA's (Standard Methods....)test.
For $21 their service is still a good deal. Do you care if you calcium is really 30 or 36 (0.3 mEq/L error)? What difference will that make in your beer?
The place where Ward Labs does fall down a bit (and part of the reason then don't get smaller cation/anion imbalances) is that they don't fully understand the relationship between alkalinity, carbonate and bicarbonate. They were using a 'standard procedure' dated 1934 (or thereabouts) from the Department of Agriculture which called, as so many alkalinity procedures do, for measurement of P and M alkalinity but were measuring P at pH 8 when it should be done at 8.3. This screwed up carbonate concentration whenever pH > 8. I pointed this out to them and they have started using 8.3 but are still not calculating carbonate correctly though bicarbonate numbers seem to be better now (I did indicate to them where they could get the correct procedures for calculating carbonate and bicarbonate but never heard back from them). As it is rare that they test water at pH > 8 this is seldom a problem.
Another place you may notice a discrepancy is between the reported levels of calcium and magnesium and the total hardness. They probably measure hardness with an automated titrator and probably measure the individual metals (including sodium and iron) with ICP (at least they advertise that they have ICP capability on their web site). Alkalinity would also be measured by automated titration. Sulfate is a tough one and probably responsible for a good part of the error in any report. It is usually done by precipitating barium sulfate and then determining that gravimetrically or by looking at the turbidity of the sample after barium chloride has been added. If the chemistry is calibrated frequently enough it is possible to get a pretty good result but I have no idea how they actually implement this test (or any of their tests). I was quite surprised that they were using the ancient DOA protocol for alkalinity but then they mostly serve the agriculture industry and the test is the same as the AWWA's (Standard Methods....)test.
For $21 their service is still a good deal. Do you care if you calcium is really 30 or 36 (0.3 mEq/L error)? What difference will that make in your beer?
