When a water supply is very soft and by soft that means a low hardness level where the water creates suds easily, washes easily, grows plants well and is pleasant as a very low mineral base to drink with any beverage.
Canberra, Darwin, Hobart, Melbourne and Sydney all have such very soft water supplies. They are all generally supplied by Reservoir water that is actually filled direct by rainfall, river systems and run off. This water supply has a low level of calcium and magnesium mineral base
First the water user must understand that water is a living item with an active mineral base.
The mineral base comprises calcium and magnesium, hardness mineral salts, sodium and chloride, the attacking mineral salts.
Older plumbing styles which were typically galvanized. Soft water will dissolve the inner pipe wall metal and send the water quite brown. The water carried can be found to also contain elevated levels of zinc.
Copper plumbing is a very soft metal and dissolves quite readily under aggressive water conditions. This will send porcelain blue or green and make the water taste quite bitter.
Old un-galvanaised iron pipes will also cause brown water to come out of the tap leaving elevated iron levels present.
An aggressive water supply will have a low hardness presence by test and a low pH that is generally not above a pH of 7.3 and more typically as low as a pH of 6.5.
Old un-galvanaised iron pipes will also cause brown water to come out of the tap leaving elevated iron levels present.
There is a calculation in water treatment that can determine the behavior of any water supply, using these factors.
These four figures are converted to calculate to a given scale, the result being the Saturation Index of Water. This calculation result advises us just where that water supply is in behavior,
aggressive, in balance or scale forming. And for a water supply to be in perfect balance and do neither the index has to have an SI result by calculation of between -.5 and +.5 at or below 25 deg C.
The water supply will not corrode or attack soft metals nor will it have an excess of calcium in the water supply that will cause scale build up at that level when used. It will do neither.