The manual for my dishwasher as well as the warning sign on a box of dishwasher salt says that you should never load food salt into the water softener because it will damage the ion exchanger.

Given that table crystal salt (with no iodine and/or ferrocyanides added) costs 20 times less than dishwasher salt and it says "99.9% NaCl + traces of other minerals" on both packs, I wondered if it is true?

Are there proven cases of a dishwasher broken through usage of table salt in the water softener?

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    What sort of device are you using? I am only familiar with the water softner devices that are huge things where you buy 40lb bags of large salt chunks and put those in. – JasonR Oct 13 '11 at 13:24
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    20 times less? Really? Where I live they have pretty much the same price... (0.5-1 euro/Kg depending on the brand) – nico Oct 13 '11 at 16:39
  • @Brightblades: a Bosch, don't remember the exact model. It has a container which you fill with the water (once) then with the salt. It fits about 300 g. of salt which is enough for about a week. – Quassnoi Oct 13 '11 at 18:14
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    @nico: crystal table salt (which is actually the cheapest kind) costs an equivalent of about 0.1 euro/kg here (in Russia), and dishwasher salt costs 2 to 3 euro/kg, depending on the brand. But which is more important, the dishwasher I'm asking about is located in the village house, and the local convenience store has detergent and rinse agent but no salt, everyone just uses crystal salt. – Quassnoi Oct 13 '11 at 18:22
  • As a side note...... I used regular table salt in my dishwasher and wrecked the pump ....a 300.00 fix..... The repairman said that table salt or any salt for that matter is corrosive..... That's why northern cars and those by the sea have rust on them. No more salt for me. – user31818 Mar 17 '16 at 19:19

The main reason that you should not use table salt is because the .1% that isn't NaCl is usually some sort of drying agent to keep the salt from clumping and caking. Furthermore, table salts tend to clog up when wet. Additionally, the size and shape of the salt crystals will play into how the water softener works. Table salt is generally very fine, and comes in much more regularly shaped crystals, whereas the type of salts used in water softeners are sized and shaped so as not to clump and stick together when wet.

By using table salts, there appears to be some customers that have broken their dishwashers.

Now, I see you mention that it is a "community" washer in the comments. This may have a different effect on what type of salt is used. Generally, industrial strength washers may have upgraded components to handle "abuse" but numerous users. it may be that your community's washer has an extra powerful pump or something to deal with the anticipated abuses. It's impossible to tell without knowing the make and model though.

Hope that helps.

  • +1, although often you'll find anticaking agents also in table salt. Also, rock salt (which is what I would use for the washing machine) does not really clog up as much. – nico Oct 14 '11 at 5:30
  • Great answer, thanks. Crystal salt available here contains no (intentional) additives (it's primarily intended for home canning and curing and additives, particularly NaI, inhibit the fermenting activity). Also it's very coarse, though the crystals are less in size that those in the dishwasher salt. BTW, your link to fixya leads to a question form, not to the actual problem. – Quassnoi Oct 14 '11 at 6:53
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    @nico, those anti-caking agents are not designed to react well in a wet environment like a water softener (like I said in my answer). In an environment like that, they actually cause more clumping than prevent it. – Larian LeQuella Oct 17 '11 at 23:02
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    @Quassnoi, yes, the type of salt for canning may actually work given what I know of that (I am not an expert, I only play one on the internet). – Larian LeQuella Oct 17 '11 at 23:03

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