Set your dishwasher’s salt level to match your local tap water hardness. Soft water (under about 60 mg/L CaCO₃, or 3.5 gpg) needs little or no salt. Water above about 180 mg/L (10.5 gpg) needs the upper levels. In between, pick a middle level. Dial scales differ by brand, so use the table below as a guide and then check your manual.
To get your own figure, use the lookup page or the hardness calculator to convert between mg/L, gpg, °dH and °fH.
What the salt actually does
Dishwasher salt is not for washing. It regenerates the built-in water softener, a small ion-exchange resin tank at the bottom of the machine. The resin swaps calcium and magnesium in the incoming water for sodium. When the resin is full, the machine flushes it with salty water and starts again.
If the resin is not regenerated, hard water reaches the wash and rinse. You then see white film on glasses, spots on cutlery and scale on the heating element. These are cosmetic and mechanical effects, not a safety issue.
The hardness setting tells the machine how often and how strongly to regenerate. A higher setting uses more salt and a little more water per cycle. A setting that is too low leaves hard water in the wash. A setting that is too high wastes salt and rinse water.
Hardness bands and typical dial settings
The table groups hardness into bands and shows the level most machines would use. The first two columns follow the USGS classes for soft, moderately hard, hard and very hard water, split further at the top end. The last column is an illustration only.
| Hardness (mg/L CaCO₃) | Hardness (gpg) | Typical level on a 1–5 scale |
|---|---|---|
| 0–60 | 0–3.5 | 1 (or salt off, if the machine allows it) |
| 61–120 | 3.6–7.0 | 2 |
| 121–180 | 7.1–10.5 | 3 |
| 181–250 | 10.6–14.6 | 4 |
| Over 250 | Over 14.6 | 5 (highest) |
Scales vary by brand. Some machines have 3 steps, some 5, some 6 or more. Some use a dial, some a button sequence, some a menu on the display. Some manuals give the table in °dH, °fH or mmol/L, not mg/L. Many machines ship set to the middle level. Always check the manual for your model before you change anything.
Conversion used here: 1 gpg is about 17.1 mg/L. The mg/L values in this guide are stored in our database. The gpg values are rounded from them.
What this looks like in real cities
The figures below come from the utility data behind each city page. Where a utility serves several zones, the city page shows a range, and your street may differ from the headline number.
Soft water. Sheffield is listed at 42.0 mg/L, about 2.5 gpg. New York is at 32.0 mg/L, about 1.9 gpg. In both, the lowest level or salt off is usually enough. If the machine has a salt-empty warning that cannot be switched off, keep a small amount in the reservoir.
Moderately hard. Denver is at 105 mg/L, about 6.1 gpg. Houston is at 110 mg/L, 6.4 gpg, and its main system ranged from 43.4 to 137 mg/L in the 2024 report. That range straddles two bands, so level 2 is a reasonable start and level 3 is the next step if spots appear.
Hard. Leeds is at 135.6 mg/L, about 7.9 gpg. Level 3 on a 5-step scale fits.
Very hard. Phoenix is at 237 mg/L, about 13.9 gpg. Bath is at 283.0 mg/L, about 16.5 gpg. Munich is at 282.0 mg/L, similar to Bath. Indianapolis is at 317 mg/L, about 18.5 gpg. Berlin has a median of 328.4 mg/L, about 19.2 gpg, with a range across its nine zones of 269.5 to 415.9 mg/L. In these cities the highest or second-highest level is normal.
If your city is not listed, find it through the lookup page.
How to set it
- Find your hardness from the utility or from your city page. Note the unit.
- Open the manual for your exact model number. Find the hardness table.
- Convert your figure to the unit the manual uses. The calculator does this.
- Pick the level whose range contains your figure. If you sit on a border, choose the lower level first.
- Follow the manual’s steps to enter the level. Methods differ: a dial inside the tub, a button sequence on the control panel, or a settings menu.
- Fill the salt reservoir with dishwasher salt only. Run a cycle straight after refilling, so spilled brine is rinsed out and does not corrode the tub.
After two weeks, look at glassware and the inside of the machine. Cloudy film that wipes off with vinegar usually points to hardness. Cloudy film that does not wipe off can be etching from soft water and too much detergent. In that case, lower the level, not raise it.
Common mistakes
- Using table salt or rock salt. These can contain additives or insoluble material that clogs the softener. Use salt sold for dishwashers.
- Setting the level once and forgetting it. If your supplier changes source or blends supplies, your hardness can change. Seasonal shifts are common where supply mixes surface water and groundwater.
- Ignoring the rinse aid. Salt handles hardness. Rinse aid handles drying and sheeting. They do different jobs.
- All-in-one tablets with salt switched off. Some manuals allow this in soft water. In hard water, it is not enough on its own.
- Not checking the salt light. The indicator shows when the reservoir is low. A first fill takes a few cycles to dissolve.
FAQ
Do I need dishwasher salt if my water is soft? Often not. Below about 60 mg/L (3.5 gpg), many manuals let you set the lowest level or switch the salt function off. Some machines still show a refill warning. If your supply is a mix of zones, keep an eye on glass spotting before you stop adding salt.
What happens if I set the level too high? The machine regenerates more often. It uses more salt and a little more water per cycle. Glassware is not harmed, but you pay for salt you do not need. Moving down one level and watching the results is a sound check.
Does a whole-house softener replace dishwasher salt? If a softener treats all water to near zero hardness, the dishwasher sees soft water and can run on the lowest level or with salt off. Check that the softener is actually delivering to the kitchen tap, and check the manual. Our city pages show the untreated mains figure, so use the softener’s own setting for treated water.
Sources
- USGS Water Science School, “Hardness of water”: https://www.usgs.gov/special-topics/water-science-school/science/hardness-water. Used for the soft, moderately hard, hard and very hard classes in mg/L.
- Berliner Wasserbetriebe, analysis data of the waterworks: https://www.bwb.de/de/assets/downloads/analysewerte-wasserwerke.pdf. Used for Berlin.
- Stadtwerke München, drinking water analysis values: https://www.swm.de/dam/doc/wasser/trinkwasser-analysewerte.pdf. Used for Munich.
- City of Phoenix Water Quality Report: https://phoenix.gov/waterqualityreport. Used for Phoenix.
- Example manufacturer manual with a hardness level table (Indesit/Whirlpool, WIE2B19): https://www.appliancesdirect.co.uk/PDFs/WIE2B19_UserManual1.PDF. Shows the typical structure: look up local hardness, then enter the matching level.
- Other city figures come from the sources named on each linked city page.
The level column in the table is a general illustration, not a manufacturer specification. Your manual overrides it.