Is softened water safe to drink?

The conversion is fixed by chemistry, so you can calculate it rather than guess. Multiply your hardness in grains per gallon by 7.5 to get the approximate sodium added in mg/L, then add whatever sodium the supply already contains. That baseline figure is reported by New Jersey utilities and is listed on each water system page on this site, which means you can produce a real number for your own house instead of working from an average.

Two consequences follow. On moderately hard water the addition is small. On very hard water — 15 to 20 grains per gallon, as found on some groundwater systems — softening adds well over 100 mg/L, which is worth knowing before you decide whether to soften the kitchen cold tap at all.

Sodium in drinking water is not federally regulated with an enforceable limit. The EPA lists it on the drinking water contaminant candidate and advisory side, with a 20 mg/L advisory level framed explicitly around individuals restricted to 500 mg/day of total sodium, and a taste threshold in the 30–60 mg/L range.

The WHO's guideline document reaches a similar position: no health-based guideline value for sodium in drinking water, with a note that concentrations above about 200 mg/L may cause an unacceptable taste. Neither body characterises softened water as unsafe for the general population, and neither treats it as appropriate for someone on a medically restricted sodium intake.

The groups usually identified are people on physician-directed sodium restriction — which in practice means some people with hypertension, heart failure or kidney disease — and, as a precaution frequently raised in the literature on infant feeding, water used to prepare formula. If you fall into one of those categories, the correct step is to ask the clinician managing your care, with your calculated figure in hand. This page is not medical advice and cannot substitute for that conversation.

It is also worth saying plainly what the evidence does not support: there is no good basis for the claim that softened water is harmful to healthy adults, and equally none for the claim that drinking softened water confers a health benefit. Both directions of overstatement are common in sales material.

The standard installation answer is to leave one tap unsoftened. Most installers will plumb the kitchen cold tap ahead of the softener as a matter of course, which preserves the mineral content for drinking and cooking while everything else in the house — water heater, laundry, showers, dishwasher — receives soft water. If that tap was not left hard, it can usually be rerouted.

A second option is potassium chloride in place of sodium chloride in the brine tank. It works identically and adds potassium instead of sodium, though it costs more per regeneration and people with kidney disease or on potassium-sparing medication have their own reason to check first. A third is reverse osmosis at the drinking tap, which removes the sodium the softener added along with most other dissolved solids; see reverse osmosis explained.

One more note that has nothing to do with sodium: softened water is more effective at dissolving lead and copper from plumbing than hard water is, because hardness scale forms a partial barrier inside pipes. In housing stock old enough to have lead solder or lead service lines, that is an argument for keeping the drinking tap hard and testing, rather than an argument against softening the house.