1. The harm of hard water to washing laundry
The hardness of water refers to the content of salts dissolved in water, that is, the content of calcium salts and magnesium salts. The higher the content, the higher the hardness, vice versa. GPG is the unit of water hardness, 1GPG means that the content of hardness ions (calcium and magnesium ions) in 1 gallon of water is 1 grain.
The standard of hard water:
According to the American WQA (Water Quality Association) standard, the hardness of water is divided into 6 levels. 0 - 0.5GPG is soft water, 0.5 - 3.5GPG is slightly hard, 3.5 - 7.0GPG is medium hard, 7.0 - 10.5GPG is hard water, 10.5 - 14.0GPG is very hard, and above 14.0GPG is extremely hard.
Hard water for washing laundry can have undesirable consequences. Calcium and magnesium ions in hard water are deposited on the fabric, causing graying of white fabrics. It will affect the whiteness and feel, and make the color of the fabric fade and lose its vividness. Moreover, calcium and magnesium ions are deposited on the fabric, and the adhesion to the fiber is quite strong. It is quite difficult to wash away the calcium and magnesium ions adhering to the fabric and make the grayed fabric white. The best way to wash white fabrics in hard water with no or less graying is to take precautions first.
Iron does not exist in water as a metal, but as an ion or an ionic compound. If this kind of water is heated to wash fabrics, rust (iron hydroxide) will be formed and deposited on the fabrics as some brown spots. It will make the white fabrics turn yellow as a whole and make the colored fabrics fade. To remove these iron scales, special treatment with acid is required. Another hazard of iron in water is that it has a certain catalytic effect on the decomposition of hypochlorite and hydrogen peroxide. In the bleaching stage, if iron ions exist in a certain part of the fabric, it will catalyze the strong decomposition of hypochlorite or hydrogen peroxide, which will make the local oxidation reaction violent and lead to the damage of the fabric.
2. Washing water requirements
Drinking water quality standards, some chemical indicators are as follows:
PH value: 6.5 - 8.5
Total hardness: ≤446ppm
Iron: ≤0.3mg/L
Manganese: ≤0.1mg/L.
Washing water requirements:
PH value: 6.5~7
Total hardness: ≤25ppm (preferably 0)
Iron: ≤0.1mg/L
Manganese: ≤0.05mg/L
Tap water is generally used in the laundry department of urban hotels. Tap water is produced according to the standard of domestic using water, and there is no problem for people to drink it. But as washing water, it is obviously not ideal. Therefore, in order to achieve high-quality washing requirements, the washing water must be treated to a certain extent.
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Post time: Nov-03-2022
