Just read this topic so apologise for the late reply.
There appears to a lot of confusion with terminology and units of measurement in this post that I hope I can clarify. A lot of the units of measurement and terminology are a result of history and don't necessarily reflect the methods used today to determine concentrations.
Alkalinity is the buffering capability of water and is generally reported as CaCO3. The alkalinity in solution is in the form of bicarbonate ions (HCO3-)
Residual Alkalinity is a brewing term and considers the affect of the reaction of Ca and Mg with phosphates in the malt to precipitate out as calcium phosphates leaving H+ ions in solution and increasing the acidity (decr pH) and neutralising some of the alkalinity. What is left is the residual alkalinity which tries to buffer or raise pH.Ca and Mg have no affect on water pH alone.
Hardness relates to the Ca and Mg in solution and usually given as CaCO3. The term hardness originally referred to the soap-consuming power of water. Basically, they form precipitates with the soap which prevented lathering.
Why are these reported as CaCO3? Simplistically, the old method of measuring alkalinity and hardness was to boil and aerate the water causing CaCO3 which is insoluble to precipitate out. This precipitate was then weighed to determine the amount of bicarbonate/ alkalinity present.
As for JP maths around /50 *20. This is a conversion of units. Generally, the units reported are ppm or mg/L. The calculation he is doing is converting it to mEq/L which is a unit that takes into account the charge of the ion. We don't need to worry too much about this as our alkalinity is reported as ppm CaCO3.
Parks the alkalinity from the test does look low. Generally, I have measured my tap water in the 60-70 ppm as CaCO3 range. You can buy test kits from aquarium stores for testing hardness and alkalinity if you are keen.
As for pH strips, go and buy a pH meter. Even the cheap ones on ebay tell you more than those strips.
From personal experience with Brisbane water, the calculators such as EZwater etc are broad estimates at the best. They can help you get in the ball park but can also be wildly wrong especially with some of the dark beers and the addition of sodium bicarbonate ( I use this instead of chalk as it is a lot more soluble - just watch the sodium addition). From actually measurements pale ales etc with some crystal are usually fine with mash pH. Dark beers will need some carbonate addition and light beers, particularly with a reasonable percent of wheat (pH @ RT = 5.7-5.8) will need some acid addition even after salts are added.
Brisbane water lacks sufficient Ca. This should be a minimum of 50ppm. I actually go a bit higher now days.
I have only touched the surface on water.
There are a lot of good resources on the web of pH etc. Have a look at www.braukaiser.com ,
http://www.wetnewf.org/. Also there is some good publications at the Institute of Brewing and Distilling. Have a look at the papers done by Tim O-Rouke (
The Role of pH In Brewing, by T O'Rourke) http://www.ibd.org.uk/cms/file/312.