How do water softener systems work? Are they magic? Adding salt gets rid of other minerals. . . HOW? I’ve never understood this. I’m 54, male.


How do water softener systems work? Are they magic? Adding salt gets rid of other minerals. . . HOW? I’ve never understood this. I’m 54, male.

In: Chemistry

They use a principle called ion exchange. They have big filter cartridges filled with plastic beads. However, the beads are made from a special type of plastic, which has negative charges on its surface. Positively charged ions – such as sodium, calcium, magnesium and so on, are attracted to the negative charges on the beads and get stuck.

Calcium and magnesium, which cause water “hardness” are more strongly positively charged than sodium, so if there is a choice, the calcium and magnesium will stick to the beads in preference to the sodium, and will push the sodium off into the water.

The first step in the process is to load the beads with sodium. This is done by taking a concentrated salt solution, and running it through the cartridge. There is so much sodium in the brine, that it pushes any calcium or magnesium off the beads. After about a 30 minute soaking time, the waste brine then goes down the drain, carrying the calcium/magnesium with it.

The cartridge then gets rinsed out with fresh water, and then gets switched in line with the water supply. As water flows past the beads, the calcium/magnesium in the water preferentially stick to the beads, and the sodium is released.

At some point, all the sodium on the beads is depleted and the beads are saturated with calcium/magnesium, and the system needs to be regenerated again – so the system mixes up a salt solution and sends it through the beads, and the process repeats. Most water softeners have a water meter or timer, which triggers regeneration – the trigger needs to be adjusted for how much calcium is in the water (and in the case of a timer system, how much water is used on a daily basis).

Water that filters through rocks picks up a chemical dissolved in the water called calcium carbonate, which is basically what goes into making seashells. When you heat the water in a kettle or boiler the calcium carbonate is deposited on the heating element creating the white “fur” by using a water softener you are removing the calcium carbonate.

There is another sort of water softening system. This uses polyphosphate salts and was common in laundry and dishwashing products. The polyphosphates bind to the magnesium and calcium ions in hard water, preventing them from reacting with soap to form scum, or precipitating out to form scale. The polyphosphates are in the product, and dont need extra equipment such as columns or filters.



Here’s how I would explain to an actual 5 year old:

The beads in the softener have millions of little hands. They hold onto regular old salt until something they like better goes by (like hardness or certain other things). When they’re full of things they like and you want them to let go (regenerate), you put a lot of salt in there and they let go of the things they had grabbed onto because they want to touch all the salt going by. When the the salt is starting to run out at the end of the rinse, there’s nothing left but salt to grab onto. So they hold onto it until something better comes by. Rinse and repeat (literally).


There’s other systems for dealing with hard water, too. The “H2FLow” anti-scale system employs “Template Assisted Crystallization,” which uses resin beads to accumulate dissolved calcium compounds into larger particles that don’t stick to pipes & shower glass, but it needs a carbon filter in front of it to remove chlorine from the water, and the carbon filter needs a sediment filter in front of it, to keep from clogging the carbon filter – so you end up with three filters in series. I’ve got two sets of these to condition the water coming into my house.

The classical “ion exchange” system to treat hard water at 10gpg (grains per gallon), you end up with 80mg/liter of sodium, about 4x the recommended limit for someone on a low-sodium diet. Some of these systems produce water with up to 300mg sodium/liter (reference below).

Salt is actually two types of atoms bound together, and they have a loose bond – once salt gets into water, it dissolves. This means the atoms float around by themselves. However, some other molecules can form from the leftovers, molecules which do not have a loose bond. These include the other minerals, which bind with parts of the dissolved salt, and drop to the bottom as solid materials, which are easily filtered out.

Now, a water softener uses some other smart tricks to remove the salt, but this is the basic version – salt dissolves, other materials form from the leftovers. We can use the same principle to clean water of lots of other unwanted things, and I recall a science project we had in high school where we went to a sewage plant and collected some, well, sewage water, and had to clean it using, basically, filtering and this method. My group’s water ended up crystal clear – but quite toxic, as we hadn’t figured out how to get the pH value down to normal levels.

Would the water that has a very slight salty taste be bad for high blood pressure?

How is your sex relevant to this?

The water softener is full of resin beads that like to grab onto the minerals that make water “hard.”

However, they eventually can’t hold any more minerals and need to be cleaned, so the water softener runs a salt water solution through the beads to rinse them off.

Then, the system is ready to use again.

Apologize my ignorance but what is hard water?

We drink nothing but water in our home, and didn’t care for the slightly salty taste, so we switched to potassium chloride instead of salt. It is FAR more expensive, but worth it because of all the water we drink. People are always commenting on how good our water tastes when they come over.

The resin beads inside do the filtering . The salt bath is what cleans the beads off of mineral deposits every 24 hours or so.

The salt doesn’t do the actual softening. It’s what revitalizes the beads.

How long do the beads work? Do they have to be replaced periodically?

Used to work for a company that sold water softeners. One thing I didn’t see mentioned below is a lot of people complain *after* putting in a water softener that they don’t feel the water gets them ‘clean’ after a shower.

The reason apparently is all those dissolved minerals in the hard water act as a mild exfoliant, and without them, people feel like their skin is not being scrubbed.

And it is those tiny dissolved minerals are the real reason for getting a softener, IMHO. We have an ice maker in the fridge, a built-in coffee machine and a dishwasher. Hard water attacks all the seals in those devices, and over times, erodes them, causing leaks and other malfunctions.

Might be worth mentioning that there are chemicals that function in a similar way called chelating agents.

They’re usually compounds, ligands with slightly negative active groups that tend to bind to positively charged ions responsible for water hardness like calcium ions. They’re used in industrial uses, as medical treatments. Hell, even haemoglobin the stuff that carries oxygen around the body functions as a chelating agent – strongly binding to Fe2+ ions which in turn acts as a reversible binding agent of oxygen for you know, helping your body functions properly.

In ELI5 terms, they’re like little hooks or claws, many are shaped like the claw in a claw machine but instead of grabbing stuffed toys they grab onto heavy metal ions.

Water filtration systems get rid of minerals, sediment, and other unwanted contaminates with various filtering strategies.

Then, separate or in-built, water softer systems will condition the water, such as using salts to adjust the water’s ‘hardness’ and re-adding healthy drinking water minerals.