How to Set Your Water Softener’s Hardness (Chart + How to Test Your Water)
Quick answer: set your softener to your untreated water’s hardness in grains per gallon (gpg). If your test result is in mg/L or ppm, divide by 17.1. If your water has iron, Whirlpool, Rheem and a common Fleck setup guide all say to add 5 to the setting for each 1 ppm of iron. For example, 20 gpg water with 2 ppm of iron gets a setting of 30. If your display shows 25 and you never changed it, that’s the factory default on Whirlpool and Rheem softeners, not your water’s hardness.
Water softener hardness setting chart
Find your test result on the left. The setting is the hardness in gpg, rounded to the nearest whole number, before any iron adjustment.
| Test result (mg/L or ppm) | Hardness (gpg) | Setting |
|---|---|---|
| 25 | 1.46 | 1 |
| 50 | 2.92 | 3 |
| 80 | 4.68 | 5 |
| 100 | 5.85 | 6 |
| 120 | 7.02 | 7 |
| 150 | 8.77 | 9 |
| 180 | 10.53 | 11 |
| 200 | 11.70 | 12 |
| 250 | 14.62 | 15 |
| 300 | 17.54 | 18 |
| 350 | 20.47 | 20 |
| 425 | 24.85 | 25 |
| 500 | 29.24 | 29 |
mg/L ÷ 17.1 = gpg. ppm and mg/L are the same for hardness. Rounded to the nearest whole number, as in the Fleck guide’s example (300 mg/L is 18 gpg).
For context, the U.S. Geological Survey calls water above 120 mg/L (about 7 gpg) hard and above 180 mg/L (about 10.5 gpg) very hard. The calculator below does the math for you, including iron, and shows where to enter the number on your softener.
Why your softener says 25 (or 20)
A setting of 25 is the factory default on Whirlpool and Rheem softeners, and the Fleck 5600SXT guide we used shows 20 on its hardness screen before you change it. Those are placeholders, not your water’s hardness. If your water is softer, the softener regenerates more often than it needs to and uses extra salt; if it’s harder, the softener runs out between regenerations and you get hard water. Quality Water For Less’s Fleck guide puts it simply: if the softener isn’t programmed with your hardness, it will regenerate either too early or too late.
Adding iron to the setting
Iron uses up the softener’s capacity too, so you add it to the hardness number. Whirlpool, Rheem and Quality Water For Less’s Fleck guide all use the same rule: add 5 for each 1 ppm of clear-water (ferrous) iron. Whirlpool’s and Rheem’s manuals give this example: 20 gpg hardness plus 2 ppm of iron is 20 + (2 × 5) = 30. Some sizing guides use 4 per ppm, as our size calculator does by default; for the setting, follow your softener’s manual. Softeners only handle dissolved iron up to their rated limit, so check our iron guide if you have a lot.
Water softener hardness setting calculator
Enter your untreated water’s test results to get the number to set.
Enter your hardness to see your setting.
How it works: mg/L ÷ 17.1 = gpg, plus 5 for each ppm of iron, rounded to the nearest whole number (minimum 1). Menu steps come from Whirlpool’s WHES48 manual, Rheem’s RHS18 manual and Quality Water For Less’s Fleck 5600SXT guide; your model may differ.
How to test your water hardness
Test the untreated water for the setting: a tap before the softener or one on the bypassed line. Rheem’s manual recommends leaving outside faucets on hard water, so an outside tap is often the easiest place. Then test softened water from a cold tap after the softener to check it’s working.
| Method | Good for | Limits |
|---|---|---|
| Your utility’s water quality report | City water; free | Covers your whole water system, not your tap, and not every report lists hardness |
| Test strips | A quick reading in seconds; cheap enough to test often | Read in color steps (0, 40, 80, 120 ppm and up on the ITS strip below), so small amounts of hardness are hard to read |
| Drop-count kit | Exact numbers; checking softened water | Takes a few minutes; costs more |
| Certified lab | Well water: also tests iron, manganese and pH | Costs more and takes days |
Water under 1 gpg (17 mg/L) counts as soft, according to North Dakota State University Extension. Strips are fine for setting the softener, but checking softened water needs finer steps than many strips have. Hach’s HA-71A drop-count kit, for example, has a low range in which each drop equals 1 mg/L. Not sure your softener is working at all? Our “is my softener working?” checker walks through the usual causes.
Best water hardness test kits
Varify Water Hardness Test Kit
A popular strip kit with plenty of strips for testing both your untreated and softened water over time. Its color chart reads in both gpg and ppm, so there’s less math.
- Range: 0–25 gpg and 0–425 ppm (listing)
- Strips: sold as a 150-strip kit, with spare strips in sealed pouches (listing)
Good to know: the chart tops out at 25 gpg, so if your water is harder, use the strips below or a drop-count kit. These details come from the seller’s listing.
Check price on AmazonIndustrial Test Systems WaterWorks Total Hardness strips
From Industrial Test Systems, a U.S. test-strip maker. The wider range covers very hard well water, up to 1,000 ppm (about 58 gpg).
- Color steps: 0, 40, 80, 120, 180, 250, 425 and 1,000 ppm (listing)
- Strips: 50 per bottle; a 3-second dip-and-read test
Good to know: the steps are wide at the top end, so a reading between 425 and 1,000 ppm is an estimate. For a precise number on very hard water, use a drop-count kit or a lab.
Check price on AmazonHach HA-71A Total Hardness Test Kit
A drop-count titration kit from Hach. You add drops of a reagent and count them until the sample changes color, which gives an actual number instead of a color match.
- Ranges: 1–20 mg/L (each drop equals 1 mg/L) and 1–20 gpg
- Tests: about 100
- Why it helps: the low range reads in 1 mg/L steps, so it can confirm softened water is under 17 mg/L (1 gpg); Hach’s instructions say a blue color at the start means soft water
Good to know: it wasn’t available on Amazon when we checked, so this button goes to Hach. Its high range tops out at 20 gpg, so for harder water use the ITS strips or a lab.
See it at HachHow to set the hardness on popular softeners
Whirlpool
- Press PROGRAM until the clock shows “CURRENT TIME,” and set the time of day.
- Press PROGRAM again: a flashing “25” and the word “HARDNESS” appear.
- Use the up and down buttons to set your hardness number, including any iron adjustment.
- Press PROGRAM again to set the “RECHARGE TIME.” The default is 2:00 AM.
Rheem
- Set the present time, then press SELECT until “HARDNESS” shows. The default is 25.
- Use the up and down buttons to set your hardness in gpg, including any iron adjustment.
- Press SELECT to reach “RECHARGE TIME.” The default is 2:00 AM, adjustable in 1-hour steps.
In California, Rheem’s manual says to turn on its salt efficiency setting so the softener runs at 4,000 grains per pound of salt or better.
Fleck 5600SXT
- Set the time, then hold the up and down buttons together for 5 seconds to enter master programming.
- Press REGEN to step through the screens. “C” is the unit capacity in thousands of grains (default 32.0 in the guide), and “H” is the hardness in gpg (default 20).
- Set “H” to your hardness including iron, and “C” from the chart below.
- The guide also sets a 15% safety reserve (“SF”), a 14-day maximum between regenerations (“DO”) and a 2:00 AM regeneration time (“RT”).
Fleck’s capacity setting depends on your tank size and hardness. A lower capacity setting uses less salt per regeneration, and per grain. Here are the values from Quality Water For Less’s guide:
| Softener size (resin) | 0–12 gpg | 12–25 gpg | 25+ gpg |
|---|---|---|---|
| 24,000 grains (0.75 cu ft) | C 15 · 4.5 lb salt | C 20 · 7.5 lb | C 24 · 11.25 lb |
| 32,000 grains (1.0 cu ft) | C 20 · 6 lb | C 27 · 10 lb | C 32 · 15 lb |
| 40,000 grains (1.25 cu ft) | C 25 · 7.5 lb | C 34 · 12.5 lb | C 40 · 18.75 lb |
| 48,000 grains (1.5 cu ft) | C 30 · 9 lb | C 41 · 15 lb | C 48 · 22.5 lb |
| 64,000 grains (2.0 cu ft) | C 40 · 12 lb | C 54 · 20 lb | C 64 · 30 lb |
| 80,000 grains (2.5 cu ft) | C 50 · 15 lb | C 68 · 25 lb | C 80 · 37.5 lb |
From Quality Water For Less’s Fleck 5600SXT guide. The guide also gives a brine-fill time for each setting, which sets the salt; use the one for your valve.
The salt savings add up: on a 48,000-grain softener, the lowest setting gets about 3,333 grains per pound of salt (30,000 ÷ 9), while the highest gets about 2,133 (48,000 ÷ 22.5). See our high-efficiency softeners for more.
Other brands
Most digital softeners ask for hardness in gpg, and many manuals use the same iron rule. Look in your manual for a “hardness” or “H” setting, and if it lists a model code, make sure it matches your softener; Rheem’s manual warns that a wrong model code makes the softener run on the wrong settings.
Other settings worth checking
- Regeneration time. 2:00 AM is the default on Whirlpool, Rheem and the Fleck guide. Rheem notes that hard water bypasses the softener if you use water during regeneration, so pick a time nobody’s using water. See water softener regeneration.
- Maximum days between regenerations. Whirlpool lets you force a regeneration every 1 to 15 days, which it suggests for water with clear-water iron to keep the resin clean.
- Salt type. Whirlpool lets you choose sodium chloride or potassium chloride; set it to the salt you use.
- After a power outage. Whirlpool says the hardness and regeneration time don’t need resetting; reset the clock only if it’s flashing.
If your water tastes salty after changing settings, see why softened water can taste salty.
Frequently asked questions
What should my water softener hardness be set at?
Your untreated water’s hardness in gpg, plus 5 for each ppm of clear-water iron if your manual uses that rule. Use the chart or calculator above to convert a mg/L or ppm result.
What does a hardness level of 25 mean on my water softener?
It means the softener is set for water of 25 gpg. On Whirlpool and Rheem softeners, 25 is the factory default, so if you never changed it, it probably doesn’t match your water. Test and reset it.
What does a hardness setting of 50 mean?
Water of 50 gpg, which is very hard, or harder water plus iron. For example, 30 gpg with 4 ppm of iron gives 30 + 20 = 50. Check your softener’s maximum hardness rating if your number is that high.
Is it bad to set the hardness too high?
It won’t give you hard water, but the softener will regenerate earlier than it needs to, using more salt and water. Too low is worse: the softener runs out before it regenerates and you get hard water.
How do I check that my setting is right?
Test the softened water a day or two after setting it. Under 1 gpg (17 mg/L) is soft. If it’s harder, retest your untreated water and check the iron adjustment.
Related guides
- What size water softener do I need? (calculator)
- Water softener regeneration explained
- How does a water softener work?
- Why does softened water taste salty?
Sources
- Whirlpool, WHES48 installation and operation manual (2023): hardness default, iron rule, recharge time, salt type, maximum days and power outages.
- Rheem, RHS18 installation and operation manual (rev. G, 2025): hardness default, iron rule, recharge time, salt efficiency and model code.
- Quality Water For Less, Fleck 5600SXT programming guide: mg/L conversion, iron rule, capacity and salt settings, and master programming.
- Hach, Total Hardness Test Kit, Model HA-71A and its instructions.
- U.S. Geological Survey, Hardness of Water.
- NDSU Extension, Water Softening (Ion Exchange), WQ1031 (revised May 2022): soft water under 1 gpg.
- Amazon listings for the Varify and Industrial Test Systems test strips, checked October 2026.