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The other day I was buying special dishwasher salt from a grocery store for about 3.5 USD a package. Later on, when I did read the contents (trying to figure out what is so magically pricey on the salt), I saw this:

Contents: 100% NaCl

But NaCl is basic, ordinary salt! For cooking purposes, I buy ordinary salt for about 0.25 USD a package.

Did I just discover lifehack? I am quite afraid to pour kitchen salt to my dishwasher. Did anyone try replacing dishwasher salt with regular (non-iodised) salt?

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  • Table salt has anticaking agent in it and it is also too fine for the dishwasher. Rocksalt on the other hand is basically the same stuff as dishwasher salt and is much cheaper. I've been using rocksalt in my dishwasher for over ten years now and everything works just fine.
    – Amots
    Commented Nov 13, 2018 at 8:45
  • Sounds like this dishwasher has a built-in water softener?
    – Mike Waters
    Commented Aug 8, 2019 at 3:23

3 Answers 3

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Salt is used to regenerate the dishwasher ion exchange column. It is vital to use pure 100% NaCl without any other additions. This is guaranteed with all products on the market. To ease filling, and dilution it also has a somewhat coarser granularity but this is not decisive.

It is possible to use any other pure NaCl-salt as a replacement but alas our table salt used for cooking isn't. There usually are several anticaking agents that would destroy the ion exchanger in our dishwasher.

It is therefore not recommended to use table salt for a dishwasher.

Note in addition: salt is usually added as a component of multi-function dishwasher tabs. In this case we do not need any salt in addition.

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  • 1
    Aren't those multi-function tabs rather impure (i.e. contain a lot of stuff other than salt)? Also, the anti-caking agent in most table salt is plain silica; chemically inert at dishwasher temperature/pressure/pH levels in absence of fluoride ion, so unless the tiny quantity present (a small fraction of 1%) physically clogs the ion exchange column, it won't do any harm.
    – Zeiss Ikon
    Commented Jan 28, 2016 at 14:00
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    @ZeissIkon: from an occasional usage I would not be too concerned as well but we hope for thousands of hours lifetime where I just would not risk it on my machine. This even more so as we don't really know how much and what additions there are.
    – Takkat
    Commented Jan 28, 2016 at 14:25
  • Okay, good link added -- I was going by the salt box (Morton brand), apparently there are several choices and plain silica isn't the most common (or the one that'll cause the most trouble).
    – Zeiss Ikon
    Commented Jan 28, 2016 at 14:58
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    The real question is: Can I use special dishwasher salt for cooking, given that it seems to be 100% pure salt?
    – abaumg
    Commented Jan 28, 2016 at 21:36
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    I've never heard of an ion exchange column, or seen a dishwasher that requires you to add salt to it. What does this do?
    – Mason Wheeler
    Commented Jan 28, 2016 at 22:02
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The salt is used in the Water Softener ("Ion Exchanger") which is built-in to the machine. I have a Water Softener for my entire house so I actually have the dishwasher's built-in softener switched OFF and therefore never have to fill it with salt.

Obviously, that just means I have to fill the house Water Softener with salt instead.

A few years ago I realised that here in the UK, we now pay 20% VAT (tax) on Water Softener salt but not on table salt because it is deemed a food product and not liable for the "luxury" tax. I decided to try using a bulk bag of catering salt in the softener.

I first asked the manufacturer of the softener if it was OK to do it. They recommended NOT to, but could not really explain why. I tried adding about 10% of the granular salt to each refill with the large tablet salt I normally use.

I have no idea why, but the machine started to behave strangely after a few fills with the table salt even though it was quite a small proportion each time. The softening action wasn't working and a sort of brown foam started appearing inside the softener. Also, the softened water started to taste of salt.

Hence, I stopped using the culinary salt in my softener once that bag was gone and I suggest it's not a good idea to try it in a valuable dishwasher.

The one tip I can recommend though is that you actually buy Water Softener salt for the dishwasher. It is exactly the same thing as you get in small bags from the supermarket - but you buy it in 25Kg bags for around £7 - probably around a fifth of the price you're paying at the moment. You just need to be careful because softener salt come in a variety of forms: granular, large granules (about 5mm), tablets (about 20mm-40mm) and blocks. I would have thought that either of the granular forms would be OK in a dishwasher.

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  • Your water softener is contaminated with iron-reducing bacteria.
    – apraetor
    Commented Jul 15, 2018 at 20:51
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    @apraetor Can you expand on your comment please?
    – Lefty
    Commented Jul 15, 2018 at 22:22
  • See this Stack Exchange article on the problem you mentioned: diy.stackexchange.com/questions/42060/… tl;dr: the brown color is caused by bacteria which can extract usable energy by oxidizing free dissolved iron in the water, producing water-insoluble iron oxide (rust). Those bacteria are what form the brown foam. Water softener salt typically includes compounds to prevent their growth. The salt you used may have had excessive free iron, or simply not had the disinfectant.
    – apraetor
    Commented Jul 17, 2018 at 0:04
  • @apraetor Thanks for that. It definitely sounds like the same brown sludge I experienced - but it's interesting that the two answers to that question both suggest this is a problem of water derived from WELLS, when my problem occurred with mains water. Also, my brown sludge was barely noticeable until I tried the cooking salt - and disappeared again when I went back to tablet salt. I think there has always been a small amount of it in my softener, but it increased about 1000 fold with the cooking salt.
    – Lefty
    Commented Jul 17, 2018 at 13:33
  • I think you're probably correct that it was always present, living in your softener. Well water, lacking chlorine's bacteriostatic effect, is a better growth medium.. but even mains water is susceptible.
    – apraetor
    Commented Dec 16, 2018 at 20:11
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Pickling salt is a salt that is used mainly for canning and manufacturing pickles. It is sodium chloride, as is table salt, but unlike most brands of table salt, it does not contain iodine or any anti caking products added.

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