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For everyone confused by this comment: In some countries you might find dishwashers with a sort of built-in water softener: https://en.wikipedia.org/wiki/Dishwasher_salt

It's not common in the United States. Some all-in-one detergent packets might contain some amount of dishwasher salt, though.

In my limited experience in the several places I've lived in the US, only one had an issue with water that was hard enough to need addressing. Most residences there had a dedicated household water softener, so even there the dishwashers didn't need to do their own softening.

Here's a nice map [1]

[1] https://homewater101.com/articles/hard-water-across-us

Another anecdote from the USA: I've only ever had problems with hard water in a house that got water from a well. Never had a problem with municipal water (although there are other contaminants in that).

Nice to be #1 in something. But that explains a lot.

From that link [1 above]: "An overwhelming 85 percent of the USA has hard water, so the likelihood that you live in state or city with hard water is high."

For a random location. Comparing the water hardness map with a population density map it seems that most are living in areas with soft water.

I'll give you an upvote for that little dive into Wikipedia. For those who haven't already swum as deep, the article on ion exchange resins[0] is also worthwhile. Turns out they are used for reprocessing spent nuclear fuel as well as softening water. Plus a few other things.

[0] https://en.m.wikipedia.org/wiki/Ion-exchange_resin

I did bad in high school chemistry, I never could understand this stuff. First, the ion exchange resin beads are washed with Na+ which bind to the beads. Second, the hard water is run through the beads and bad stuff like Mg2+ has a stronger attraction to the beads than Na+, so the Na+ is pushed off and Mg2+ binds to beads. The resulting water out of tap is softer because Mg2+ is out, but saltier because Na+ is in. Then once in a while the beads are flushed with Na+ again with the Mg2+ being sent down the drain... but how does this happen if Na+ has a weaker bond? How can it push the Mg2+ off the beads??

The concentration matters. Concentrated Na will displace Mg, but in the Na concentration in the tap water Mg will displace Na. If you had a concentrated brine with large amounts of both sodium and magnesium, the Mg would win.

I believe the Mg+ Ca+ have a stronger attraction to the Cl- ions in the salt so when soaked in brine they trade places with the Na+

Beads prefer Mg over Na but Mg prefers Cl over beads. So you can recharge with salt brine.

Or it might just be a concentration thing where Na / Mg ratio wants to be the same in the brine and beads. So you just give a really strong brine and most of the Mg etc leaves the beads.

Ca²⁺ is the more important ion, since limescale is mainly calcium carbonate (CaCO₃). Otherwise, the explanation is fine.

The exchange of the ions is driven be the difference in concentration between water and resin surface. It works both ways, but Ca²⁺ is preferred (=stronger bonds) by the binding groups (e.g. carboxylate salts). That's why a concentrated Na⁺-brine is needed to flush out the calcium ions.

Imagine the bonding as reaching an equilibrium where Mg2+ bonds and then dissociates in a repeating cycle. If you flood that solution with Na+, the chances for Mg2+ to bond after dissociating are lower when an excess of Na+ is doing the same thing, and a new equilibrium is reached.

As explained, it's the concentration. If you don't have a dishwasher with a water softener: You don't sprinkle a little salt in some compartment, it's large and filled with 1-2 pounds of salt to make a saturated brine. The salt sold for dishwashers is purified NaCl (table salt has some other stuff like anti-caking agent). That's what the dishwasher uses to drive the Ca2 and Mg2 off the resin.

"It's not common in the United States."

If US folks are looking for this feature, it can be found on higher end Bosch dishwashers in the US.

I have very hard water and a Bosch benchmark series. The water softener makes a huge difference. I don't want a whole-house softener because I don't enjoy the feel of softened water in the shower.

We had a Bosch dishwasher with a built-in water softener when we lived in Lake in the Hills, IL, a suburb of Chicago. The municipal water there (from wells) was extremely hard and it made a big difference.

We now have a Bosch dishwasher in another house in NY state. The water is not hard (it's from one of the Finger Lakes), and the dishwasher does not have a softener, but we like the brand. After reading this story we looked up how to tweak the rinse aid dispenser and turned it down from "5" to "1".

Why don't you like the softener water? I thought it was better for the skin.

It's easier to rinse soap off with hard water.

Softened water feels slimy to me - similar to seawater.

I actually do have a whole-house softener which came with my house. I installed a bypass valve so it does not feed the pipes in my home.

It may be over-softening. Our water felt slimy until we replaced our old unit. The new unit uses way less salt (at least 10x less) and the water feels normal.

I believe the old ones had an adjustment, but I can confirm new units definitely do. We hardly use any salt at all.

Everyone I've ever known with water hard enough to be a bother just installs a whole-house water softener, so all the water inside the house is already softened. Seems inefficient to soften only the dishwasher when a whole house system is pretty cheap.

How could it be less efficient to soften less water?

Fisher & Paykel dish drawers have a salt-dispenser, at least my 2004 models do. They are (were?) designed in New Zealand but sold in the U.S. For a while they were sold rebranded by KitchenAid. My water isn't hard though so I haven't had to use any salt.

(Aside, and I don't know if they are still any good, but these dish drawers are really well engineered. Mine had some problems early on that were resolved by small changes in the design, but FP provided me the parts to retrofit my washers. They've been nearly trouble free since then.)

They were bought out by Haier a few years ago, they still exist as a brand in NZ, not sure about elsewhere. Anecdotally not as good as they used to be.

Available in the UK too. I don't have experience with the drawers (that's the dream though - fridge/freezer especially, drawers for everything (below waist height) makes so much more sense to me) but I'm familiar with a couple of more recent (last couple of years, definitely post-Haier) appliances that are pretty nice. You pay for it though... Seems roughly like Skoda/VW/Audi in terms of top-end F&P branded units with nicer fit and finish than fairly similar but much cheaper Haier branded ones.

I was looking for a fridge-freezer specifically, considered Haier but went with Liebherr in the end - I like that (in terms of white goods/kitchen appliances) it only makes refrigeration units, other than where you use them there's nothing tying them together in why a manufacturer would be good at making them all really, makes sense to specialise in refrigeration, or dish washing, or gas products or whatever IMO.

The H series F&P dishwasher models have a built-in water softener. [0]

According to the user guide, a water softener is recommended if your municipal water hardness is >250ppm which would be quite hard for municipal tap water.

In my region of central Florida the city’s water quality report shows a hardness well below 250ppm, Which you can divide by 17.1 to determine how many grains of salt to take that with.

[0] https://www.fisherpaykel.com/us/dishwashing/all-dishwashers/

Fill the salt? Configure for water hardness?

I've never heard of either of these things before. Certainly not things on my, relatively fancy, dishwasher.

https://en.wikipedia.org/wiki/Dishwasher_salt

The water hardness setting determines how much the water softener tries to soften the water.

If the water isn't soft enough, it will leave spots on the dishes. Hence people use "rinse aid", so the improperly softened water would drip off before it leaves spots.

If the water is properly softened it contains no calcium etc. which could cause spots on your dishes.

Ditto, no clue what either of those mean. Never, ever heard of adding salt to a dishwasher, certainly. Not in new ones, not in ones from the bad ol' days when they used way more water but actually worked.

I have a new one (a few years old) and yes there's a compartment for salt. My previous one did as well. I'm in Europe (Spain) if that helps. I don't go to any special store to buy them, any old Lidl or other supermarket has it. Where you from where this isn't a thing?

From other comments it's looking like this one of those US/European divide things, with compartments for salt being uncommon on US dishwashers except for a few rare higher-end models/brands that are likely common to both continents (due to low volume in the US not justifying a localized version, I'd guess). I'm middle-aged and in the US and this thread is the first time I've heard of adding salt to a dishwasher.

Seems to be not quite EU/US. At least in Ireland we don't have salt compartments either. Maybe an anglosphere/not division?

Really odd that it differs so close to neighbouring countries. Here (UK) I've never seen a Dishwasher without a salt hole, and there's often several well know brands of salt in the supermarket (no idea why, its all the same stuff).

I wonder if its based on average water hardness in the area. I'm in the north of England and our supply comes out of Buxton Springs (yep the same as Buxton bottled water) and is extremly soft so despite filling the salt it never asks for it to be refilled again as its not needed.

When I used to live in north London I'd be filling it up once a month as the water there is extremely hard - so hard that it'll kill your kettle within a year if you don't keep on top of descaling.

In the US you would install a house water softener that would soften the water when it comes into the house. It would only be used in areas with hard water. Our dishwashers usually use hot water rinses instead of cold water like European style ones, the hot water heaters will soft the water before it gets to the appliance.

Ireland has very hard water for the most part so I don't think that'd be the reason.

Anecdotes are not data and all that. The dishwasher in my house is a NEFF, and it has a salt compartment. Came with the house, built-in unit. So yes, some Irish houses have dishwashers with salt - sample size 1.

> At least in Ireland we don't have salt compartments either

I'm pretty sure the majority of dishwashers sold here have salt compartments - I've never seen one without one.

Much of Ireland has very hard water.

US consumers are easier to sell to, perhaps.

Except for the various ethnic groups who are very proud of not using their dishwasher at all.

They use it alright (as a pantry/place to store dishes).

I’ve never seen a dishwasher without this :)

But I think most people here in the Netherlands never set it up correctly and go for “all in 1” tabs. I never do, always set it up correctly. I do feel I need rinse aid to not have that nasty feel to the glasses.

In the US we have whole home water softeners when necessary, in the EU they’re built in to dish washers.

Just small differences in water treatment and quality.

Miele has it. It's a reservoir with a twist-cover at the bottom of the dishwasher that you fill with salt whenever the dishwasher tells you its time. Seems to be about once a quarter.

Apparently in Europe and some other countries they don't do whole house water softeners?

Interestingly enough as normal as salt containers are in dishwashers as 'uncommon' are house wide water softeners to me.

I know a few people who have a single outlet for osmosis water, I use a optional water filter in the kitchen outlet for drinking water.

But nobody I know is softening their whole water supply. Why soften toilet water? Why soften cleaning water? Garden water?

Well for the last 2 I guess it depends on how hard it really is

Softening toilet water means there’s less limes SLE build up in the bowl and around the rim which means the toilet is easier to clean.

Softening cleaning water means your clothes come out - well, quite literally softer. And last longer.

My dishwasher doesn't have a salt compartment or any sort of water-softening features; in the US, I haven't heard about this feature. Apparently it's a UK thing?

I know Miele has a water softener feature. That's the only time I've heard of it in the US.

There are a few Bosch models with dishwasher salt dispensers, but it’s extremely rare in the US.

It’s a great idea, given most municipalities have hard water.

Yeah I need it with my well water. But generally we just put up with spotty dinnerware. If we have guests over, we'll wash whatever by hand before.

interesting.. I got a Kitchenaid but maybe I would have gotten a Bosch. I wanted a Bosch but they were on tremendous backorder compared to the Kitchenaid in 2021.

Fill the salt? I'm not sure all dishwashers have a receptacle for that. Ours doesn't, and I'm pretty confident that I've never had one that did across several states in the US and one place in Belgium.

Is the salt for doing a softening process that substitutes for a whole house softener if you don't have one?

We live in a place with hard water and have no softener in the house (you should see our electric kettle when we haven't cleaned it recently). Recently the accumulation of what I assume to be mineral film has gotten a bit noticeable on the dishes that go in the dishwasher.

My dishwasher has a "salt" light that lights up when the salt is low.

The dishwasher is also 30 years old. Miele G 680 SC from 1992. Living in New York. Perhaps adding salt was more common in older models.

I have a new-ish Miele which has it. Good thing too, because we have really hard water here.

> and one place in Belgium.

You might not have paid attention to it because your didn't know about it, but I don't think there are any dishwashers in Belgium that don't use salt, at least for the last twenty years or so.

1) Thanks for the reminder that I'm getting old :-)

2) IIRC, that house had a whole house softener.

> - always fill the salt.

rinse aid is for hard water. restaurants probably tend to not treat the water and the commercial dishwashers they use probably tend to not have a provision for salt. they operate very differently than your residential dishwasher.

So yes, completely unneeded if you have soft water. Most dishwashers don't have a provision for salt.

Also completely unneeded if you don't mind spots.

I have hard water and a dishwasher with a softener. The plates are dramatically cleaner if there's salt in the softener, no matter what detergent i use.

> 30 years old dishwasher, super hard water.

This is the real key, modern dishwashers have so many limitations in an attempt to reduce water and power usage they do an awful job. I wish there was more information on how to disable these features.

Clear European give away.

> Apparently US folks often have dishwashers which don't soften the water. Ugh. In Europe I haven't even heard that such a thing exists!

I've only come across this in Spain so far. Never seen in Norway. But maybe I just haven't been paying attention. Then again, the water in Norway in :chefskiss:

Have never used rinse aid even once.