Dishwasher Salt – Frequently Asked Questions


It’s always frustrating when your dishwasher starts blinking red and accusing you of being low on dishwasher salt. ‘Didn’t I just fill that?’ is likely the immediate reaction. However in certain instances, you can just leave it to blink…

Is dishwasher salt just table salt by another name?

Actually, no. While, like table salt, dishwasher salt is 95% sodium chloride, it also boasts a small percentage of sodium ferrocyanide, an anticaking agent which promotes dissolution.

In that case, can I use Table Salt in my dishwasher?

Again, no. Dishwasher Salt granules are intentionally larger. This way they dissolve at a more measured rate and are unlikely to slip through the filters and damage any mechanisms. Table salt would do just that.

If I add too much salt, won’t it cake my dishes?

The salt you add to your dishwasher (provided you put it in the right compartment!) never comes into contact with the actual dishes being washed. Instead it’s pumped directly to a basket-like contraption which house the dishwasher’s resin balls.

What function does dishwasher salt serve then?

Basically it aids in the water softening process, which breaks down lime scale build up, which is indicative of hard water.

How exactly is the water softened?

Without getting too technical, it prompts ‘ion exchange’.The addition of dishwater salt activates the machine’s resin balls by giving them an ionic charge. Calcium and Magnesium atoms, which constitute lime scale, carry an opposing charge. Thus they are attracted to the resin itself as opposed to the dishwasher mechanisms and scaly build-up is avoided.

So I always need to use Dishwasher Salt?

Not necessarily. Dishwasher salt is recommended if you live in a hard water area and lack the aid of an external water-softener. If, however, you live in a soft water area, you don’t need to salt your dishwasher… despite what that blinking red light might say!

How can I check if I live in a soft water area?

For the record, Dublin City Centre is a soft water area. But if you’re unsure, you should contact your local city or county council or check their associated websites. If your water is supplied by the Leixlip Water Treatment plant however, there is a good chance it’s hard.

Does this also mean I can stop using Rinse Aid and Dishwater Tablets?

Only if you’re happy to eat off dirty plates!This article is concerned with the utility of dishwater salt specifically. But even if you have access to soft water, as a rule of thumb, we’d suggest you stick with the rinse aid and dishwater tablets.

Feel free to shop our edit of energy efficient, deep cleaning dishwashers right here!

In Short: Dishwasher Salt is a curious ingredient in the whole dishwasher process. But what does it do? And do you need it?

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Posts from the Harvey Norman blog team.

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