In softened water all calcium and magnesium ions have been exchanged for sodium ions. That means that all hardness (lime) of the water has disappeared, but all other salts have remained in the water. However, now they do not tend to precipitate as lime on glasses, tableware and cutlery. Not until the moment the water is allowed to evaporate will there be lime stains on glasses and tableware. Consequently it is necessary to wipe off the dishes to obtain a good result.
A softening plant must be regenerated with salt and it takes time. However, if you do not have great amounts of dishes and have the time to wipe it off, then a softening plant is a cheap and sensible way to obtain a decent dish washing.
Partially desalinated water is water where calcium and magnesium ions have been exchanged for sodium ions (all calcium has been removed from the water) but besides this all bicarbonates have been removed. This means that now less than half of the original amount of salts and minerals are left in the water. Glasses will still be nicer if they are wiped off, but cutlery and tableware looks decent enough to be put in its place.
A partial desalination plant contains two types of resin in a certain proportion and consequently must be regenerated in accordance with careful directions. Therefore it is usually done at the supplier's, The plant is simply replaced by a fully regenerated plant, so seen from the customer's point of view there is no maintenance, salt consumption or water waste.
Totally desalinated water is a must if you have large amounts of dishes and no time for wiping and polishing. The water is completely free of salts why post polishing is quite unnecessary - and still the dishes look like they were hand polished. Totally desalinated water is obtained either by using double ion exchange technology or by using reverse osmosis technology. The most commonly used form today is reverse osmosis because the plant is almost maintenance free. Under pressure the water is pressed through a semi-permeable membrane which retains 99 % of all salts and minerals. Also microbiological pollution, virus, pyrogenics and endotoxins are removed. Actually the water only contains H2O when treatment is completed.
As mentioned there is not much maintenance on an RO plant - however, the membrane must be cleaned or replaced when it gets clogged. So, if you want to be sure to have completely spotless dishes without manual polishing, your choice should be an RO plant. It is cheap to operate at a large water consumption and no chemicals are used.
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