Lanfax Labs in association with Choice tested 49 powder detergent concentrates in early 2007, resulting in "Wash Only" data for 35 powders in front loaders and 35 powders in top loaders. The report was published in "Choice" in the April edition. The data below extend to dual testing of products where one brand was suitable for both front and top loader.These data are presented independently of "Choice".
SALINITY
Salinity is a measure of all the dissolved solids in an aqueous (water) solution. Salinity is related to electrical conductivity, that is the ability of a solution to conduct electricity. Electrical conductivity is measured using an electronic instrument and the units of measure are deciSiemens per metre (dS/m). Common units include milliSiemens per centimetre (mS/cm) which are the same as dS/m, or microSiemens per centimetre (uS/cm) of which there are 1000 in 1 dS/m. Electrical conductivity is converted to salinity (mg/L) by accounting for a proportion of dissolved solids that do not alter the electrical conductivity.
Salinity issues involve the ability of plants to survive in soil that has a high salt content and the likely adverse impact of high saline waters on the soil physical properties. High salinity in irrigation water may affect a plant's ability to take up water because of the osmotic effect of high soil salinity, the plant will appear as though it is lacking water (induced drought). Under extremely saline conditions, only a few plants are able to survive. For irrigation purposes, the ideal cut-off for water quality is less than 1 g/L (equivalent to about 1.5 dS/m).
It is interesting to note in Graph 102A, that the highest measured salinity is for the powders specifically formulated for the front loaders and many of the "generic" branded products even at the top loading machine rate. When powders suitable for both top and front loaders are used in front loaders, the salinity may be higher than reported above unless the quantity of powder required per load is reduced (possibly halved).
Interpretation: The longer the bar, the more highly saline the "wash only" water from the respective products. Diluting the "wash water" with the "rinse" water will have an effect of dilution. This dilution decreases the salinity but also allows the water to be spread over a larger area - thereby limiting the damage that highly saline "wash water" may have. Further reduction may be gained by reducing the amount of powder used in the wash.
Several effects of extremely high salinity are that the soil become "fluffy", the permeability may increase (water moves through the soil faster), a white powder appears on the surface when the soil dries, very few plants survive and the soil is prone to erosion. That is not an effect that you desire on your lawns or in the garden.
Salinity and sodicity (specific effects of sodium) are not the same and require different techniques to overcome high levels.
Figure 102C provides a summary of the detergents and shows that the highest levels of salinity (as measured by EC) are from the majority of the detergents when mixed in front loaders. Without dilution, these highly saline liquids should not be used regularly on your favourite garden or lawn.
TOWN WATER QUALITY
All water used for washing adds some additional salinity to the
wash water. Rainwater is sufficiently low as to not be of any consequence.
Town water will vary with location, depending upon the source of the water and
the treatment it receives. Water authorities add chemicals (salts) to the
water during treatment and some of these remain in the water that is delivered
to the consumers. Depending upon where you live, there may be substantial
additional salts from the town water supply.
Total salt content measured as grams of detergent per wash
From the two graphs 103A and 103B you can calculate the number of washes per kilogram and then with the cost of the detergent ($/kg) you can calculate the cost per wash. Of course, it would be helpful if the manufacturer would label the packet with the number of washes per packet (as BioZet does) and then you could make an informed decision in the supermarket (maybe it's intended that you do not do that). So much for sensible labelling!!
1000 grams = 1 kilogram