Water softeners: how they work, and whether you need one.
A water softener removes the calcium and magnesium that make water hard. It can stop scale and reduce spotting, but it also adds sodium, uses salt and water, and costs money to buy and run. This page explains the trade-offs using the sources listed at the end. I am not a water-treatment professional, so I have stuck to what these university, WHO, EPA and Health Canada documents say and linked each one.
What a softener does
Most household softeners use ion exchange. Water flows through a tank of resin beads that hold sodium. Calcium and magnesium in the water stick to the beads and sodium is released in their place. When the beads are full they are cleaned (“regenerated”) by flushing them with salty brine, which washes the calcium and magnesium down the drain. Regeneration takes roughly one to two hours and the unit then goes back to softening (1, 2).
A softener changes the hardness minerals only. According to the Nebraska extension guide it does not remove bacteria, hydrogen sulfide, sediment, lead, nitrate or pesticides, although it can reduce small amounts of dissolved iron and manganese depending on the unit (1).
Types you will see
- Salt-based ion-exchange softeners. The standard type described above, sold as a whole-house unit. They differ mainly in how regeneration is triggered: by a timer, by the operator, or on demand according to water use (“demand-initiated”), which can use less salt and water. Some services swap a rental tank instead of regenerating at your home (1).
- Potassium-based softeners. These use potassium chloride instead of sodium chloride. It costs more and needs roughly 10% more salt (2). Health Canada publishes separate guidance on potassium from water softeners; people with kidney problems or on certain medications should ask a doctor first.
- “Salt-free” conditioners and descalers. These are sold as softeners but work differently and do not remove calcium and magnesium; they are meant to change how scale forms. I have not found independent government or university testing I can cite, so I neither recommend nor rule them out. If you consider one, ask for independent test results and check what the guarantee covers.
The pros
- Less scale. Ion exchange removes nearly all the calcium and magnesium, so there is less build-up on heating elements and fixtures (1).
- Less spotting and film. Glassware, taps and shower screens stay cleaner (2).
- Less detergent and soap needed. NDSU lists reduced detergent and shampoo use as a benefit, as well as softer-feeling laundry (2).
- Possibly longer appliance life. NDSU lists this as an advantage for washers, dishwashers and water heaters. I could not find independent figures for how much longer, so treat it as likely rather than guaranteed (2).
The cons
- Added sodium. Both extension guides give about 8 mg/L of sodium for every grain per gallon (gpg) of hardness removed. Their example: water at 10 gpg (about 171 mg/L) gains roughly 80 mg/L (1, 2). The US EPA notes that domestic softeners can raise sodium to more than 300 mg/L (3). See the health section below.
- Salt and maintenance. The brine tank needs topping up with suitable salt and checking regularly, and the valves should be cleaned and inspected at least yearly (1).
- Water use. The Nebraska guide says each regeneration uses about 50 US gallons (roughly 190 litres) (1).
- Load on septic and sewer systems. Both guides warn that regeneration water can burden a small septic or sewer system. Local rules differ, so check with your council or water utility before installing one (2).
- Not for every use. Both guides advise against watering plants or lawns with softened water because of the sodium. NDSU says steam irons and evaporative coolers should use distilled or reverse-osmosis water instead, and appliance manuals may limit softened water, so check yours (1, 2).
- Cost. NDSU (2022) gave US retail prices of about US$400 to US$2,700 for a unit, plus salt at roughly US$5 to US$10 per 40-pound bag (potassium chloride up to US$25). Prices differ by country, and installation and servicing are extra (2).
Sodium and health
Hardness itself is not a health concern. The WHO proposes no health-based guideline value for it because it is not of health concern at the levels found in drinking water; it matters for taste, scale and acceptability (4). The softening process is what adds sodium, which matters for some people.
- For people on a very low-sodium diet (500 mg/day), the EPA recommends that drinking-water sodium not exceed 20 mg/L, and says people on restricted diets should talk to their health care provider (3).
- Health Canada’s guide for seniors says softened water should not be used for drinking or food preparation because of sodium or potassium (5).
- A common fix is to leave one kitchen cold tap unsoftened for drinking and cooking (1, 2).
This is general information, not medical advice. If you have high blood pressure, kidney disease, are pregnant or are preparing infant formula, ask your doctor or pharmacist.
Do you need one?
Start with your hardness (use the checker or your utility’s report). NDSU, citing NSF International, says consumers typically notice problems above roughly 6 to 7 gpg (about 100 to 120 mg/L) (2). As a rough guide, using our bands:
| Your water | What this usually means |
|---|---|
| Soft (0–60 mg/L) | A softener is unlikely to be worthwhile. |
| Moderately hard (61–120 mg/L) | Often manageable with appliance settings and occasional descaling. Consider a softener only if scale or spotting really bothers you. |
| Hard (121–180 mg/L) | Worth comparing a softener against appliance-level measures, weighing the costs and cons above. |
| Very hard (181+ mg/L) | Scale builds quickly, so a softener or similar system is worth serious consideration. Check appliance manuals first. |
The extension guides recommend testing your water before buying, buying only what you need, and looking for certification from NSF/ANSI or the Water Quality Association. The Nebraska guide notes that in the US no federal, state or local law regulates the performance of home softeners (2014), so certification and the seller’s guarantee matter (1, 2).
Cheaper things to try first
- Use the hardness setting and salt in your dishwasher if it has one, and follow your manual.
- Descale kettles and coffee machines on the schedule your manual gives. See how to match a reading to your appliance manual.
- Use the detergent dose that matches your hardness.
- Test your actual tap water before spending money, because a city average may not match your home.
Frequently asked questions
Is softened water safe to drink?
Hardness itself is not a health concern, but softening adds sodium (or potassium). Agencies advise that people on sodium-restricted diets, with kidney problems or on certain medications ask a doctor, and Health Canada’s environmental health guide for seniors at home says softened water should not be used for drinking or food preparation. Many households keep one unsoftened tap for drinking.
How much salt does a softener use?
It depends on the model, your hardness and your water use. Demand-initiated units can use less than timer-based ones. Your installer or the manual can give figures for your unit.
Do softeners remove other contaminants?
Not in general. They target hardness. The Nebraska guide lists bacteria, lead, nitrate and pesticides among things they do not remove.
Will it fix hard water for my coffee machine?
It reduces scale, but check your coffee machine’s manual first, because manufacturers can have specific water requirements.
Sources
- Skipton, S. O. and Dvorak, B. I. Drinking Water Treatment: Water Softening (Ion Exchange), NebGuide G1491. University of Nebraska–Lincoln Extension, revised 2014.
- Scherer, T. et al. Water Softening (Ion Exchange), WQ1031. NDSU Extension, revised May 2022.
- US Environmental Protection Agency. Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sodium, EPA 822-R-03-006, February 2003.
- World Health Organization. Hardness in drinking-water (guidelines background and fact sheet).
- Health Canada. Is Your Home Healthy: Easy Steps to Maintaining a Healthy Home (environmental health guide for seniors at home).
The US documents use US units and prices; the sodium and hardness figures translate directly (1 gpg is about 17.1 mg/L). We do not use softener retailers’ websites as sources. If you spot an error, tell me. Related: Water hardness by city · Methodology.