What Does Dishwasher Salt Do? Everything You Need to Know

If you already use detergent and rinse aid, "dishwasher salt" can sound like one product too many. It does a separate job, though: it keeps the dishwasher's built-in water softener working, which protects the machine and stops your glasses going cloudy. Skipping it won't cause problems overnight, but over months and years it can damage the dishwasher and waste energy.

This guide covers what dishwasher salt does, where it goes, how often to refill it, why table salt won't do, and a few settings most people never touch.

What dishwasher salt is for

Dishwasher salt has nothing to do with flavour or disinfecting. It's there to soften water. In many homes the tap water carries calcium and magnesium. That's what "hard water" means, and it leaves limescale on heating elements and a chalky film on glassware.

Your dishwasher has a built-in softener filled with resin beads. The beads grab calcium and magnesium ions, but after a while they can't hold any more. Dishwasher salt flushes the minerals off and recharges the beads with sodium. Without it the softener stops working, and you start to see cloudy glasses, film on plates and dishes that don't come out as clean.

Why it matters even if your dishes look clean

At first, going without salt might not seem to matter. With a strong detergent you may not see spots or streaks for a while. Inside the machine, though, hard water is doing damage:

• Limescale builds up on the spray arms and weakens the water flow.
  
  

• Calcium coats the heating element, so it takes more energy to heat the water.
  
  

• The motor and pipes gradually clog.
  
  

It works a bit like plaque on teeth. Nothing hurts at the start, but leave it long enough and you get a big repair bill. Dishwasher salt is cheap prevention.

Where to put dishwasher salt

The salt doesn't go in the detergent drawer. Most dishwashers have a separate salt compartment, usually under the lower rack, with a screw cap.

To fill it:

• Take out the bottom rack.
  
  

• Unscrew the cap on the salt compartment.
  
  

• Pour in dishwasher salt until it's full. A small funnel helps avoid spills.
  
  

• Wipe up any loose grains. Salt left on the floor of the dishwasher can cause rust.
  
  

Some models have a light that comes on when it needs refilling. If yours doesn't, check it every 3 to 4 weeks.

Do I need dishwasher salt if I use all-in-one tablets?

Lots of people use all-in-one or 3-in-1 tablets and assume they don't need extra salt. Most guides don't mention the catch:

• Tablets contain very little salt and it dissolves quickly. It can't keep the softener beads recharged over many cycles.
  
  

• Tablets are fine in soft water areas but don't protect against medium or hard water.
  
  

• White streaks on black plates, or cloudy glasses even with premium tablets, mean the softener isn't being recharged.
  
  

Unless a water test shows your supply is very soft, use dishwasher salt as well.

How often you need to refill it

That depends on your water hardness and how much you use the dishwasher.

• In soft water areas, you might refill every 2 to 3 months.
  
  

• In medium to hard water areas, every 3 to 4 weeks is normal.
  
  

• If you run the dishwasher twice a day, expect to refill more often.
  
  

It's worth testing your water hardness at home with strips or a kit. Then you can set the dishwasher's salt consumption to match your water. Many people don't know this setting exists, and getting it right saves money because the machine stops using more salt than it needs.

Can I use table salt instead?

This is one of the most common mistakes. Table salt, sea salt and rock salt are not safe substitutes. They contain additives such as anti-caking agents and iodine, which can clog the softener compartment or scratch dishes.

Dishwasher salt is coarse, pure sodium chloride. The larger grains dissolve slowly, so the softener gets a steady recharge.

A few things most people don't know

• Most models let you set the water hardness level manually. If it's set wrong, the machine uses too little or too much salt.
  
  

• Salt and rinse aid do different jobs. Salt softens the water, while rinse aid reduces surface tension so droplets don't form. Hard water areas often need both.
  
  

• Fill the salt compartment right before a wash cycle. Grains spilled inside the tub can corrode stainless steel if they sit there for long.
  
  

• A funnel stops waste and keeps salt off the bottom of the dishwasher.
  
  

• If you move house, check the local water report. Your water hardness may be different, and your salt setting should change with it.
  
  

How dishwasher salt saves money

It feels like an extra purchase, but dishwasher salt is one of the cheapest bits of maintenance you can do. Without it, limescale makes the dishwasher use more electricity, makes detergent less effective and shortens the life of parts like the heating element. Fixing hard water damage can cost far more than years of salt.

In short

Dishwasher salt keeps hard water in check, protects the machine, helps your detergent work and gets dishes cleaner. Skipping it tends to cause damage you can't see and higher running costs.

Use the right salt, refill it on time and set the machine to your water hardness.

You'll find dishwasher salt alongside the rest of our sustainable home decor range.