Whole-house softening, sized to your water and your household

What hard water is

Hardness is dissolved calcium and magnesium picked up as groundwater moves through limestone and other mineral-bearing rock. It is measured in grains per gallon (gpg) or milligrams per liter (mg/L, sometimes written as ppm); 1 gpg is about 17.1 mg/L. Hardness is not a health concern. It is a nuisance and a maintenance cost: it leaves scale on anything water touches when heated or evaporated, and it reacts with soap to form the film that makes skin feel dry and glassware look cloudy.

Signs you may have hard water

• White or chalky scale on faucets, showerheads, and the inside of kettles.
• Spots and film on dishes and glassware, even from the dishwasher.
• Soap that does not lather well; soap scum on tubs and shower doors.
• Stiff laundry and dingy whites.
• Reduced water-heater efficiency and shorter appliance life as scale builds inside.

Some of these signs have other causes. Our guide to signs of hard water explains what else to rule out, and the in-home assessment measures hardness directly so the decision rests on a number, not a symptom.

How ion-exchange softening works

A softener contains a bed of resin beads. As hard water passes through, the beads hold onto calcium and magnesium ions and release sodium or potassium ions in their place. The water leaving the tank is "soft": the hardness minerals are gone, replaced by a small amount of sodium or potassium.

The resin eventually fills with hardness minerals. The control valve then runs a regeneration cycle: it draws brine from a separate tank, rinses the resin so it releases the collected minerals and recharges with sodium or potassium, and sends the rinse water to a drain. Modern demand-initiated valves regenerate based on measured water use rather than a fixed calendar, which saves salt and water. The Puronics iGen valve on the systems we install keeps 60 days of usage history for this purpose and maintains an automatic reserve so the home does not run out of treated water mid-cycle.

Sizing considerations

Sizing a softener is a calculation, not a guess: measured hardness (plus an allowance for iron if present) multiplied by daily water use gives the grains of hardness the resin must remove between regenerations. The right system balances resin capacity against regeneration frequency, flow rate, and the number of bathrooms so that pressure holds up when several fixtures run at once. Undersized systems regenerate constantly and wear out resin; oversized systems waste money and can regenerate too rarely. This is one of the main reasons we test and inspect at home before quoting.

Salt, potassium and regeneration

• Sodium chloride (softener salt) is the common regenerant. The sodium added to softened water is modest at typical hardness levels, but anyone on a sodium-restricted diet should discuss it with their physician and may prefer a reverse-osmosis system for drinking water.
• Potassium chloride works the same way and adds potassium instead of sodium. It costs more per bag and is a reasonable choice for households that want to avoid added sodium.
• Regeneration uses water and sends it to drain; a nearby drain and a standard electrical outlet are required for the control valve.

Owning a softener

Day to day, a softener asks very little: keep the brine tank stocked, glance at the display occasionally, and keep the area around the equipment accessible. Over the long term, resin eventually wears and valve components may need service; the manufacturer's written limited warranty and the owner's manual set the terms. Our guide to cost and ownership covers what to budget for.

What a softener does not do

Softening combined with filtration

Most municipal homes in our area have both hardness and chlorine or chloramine. The Puronics C-series systems we install, the Defender, Hydronex and Terminator iGen C, combine softening resin with ChloroShield Clearess filtration media and a clarifier layer in a single tank under one control valve, so one system handles both jobs. See whole-house filtration for the filtration side and compare systems for the differences between the three.