Soft Water - Important Health Advice on the Effects of Softening Water

Softening water is often very helpful as it has a number of benefits, in particular reducing scale build-up and sometimes improving the taste. However, softening it also has a certain effects on human health and also on the environment which are important to consider.

The hard water to be treated passes through a bed of the resin which contains sodium and potassium ions. As the water passes through the resin, the hardness ions are trapped in the resin and replaced by the sodium or potassium ions which are released into the water - effectively softening it. The harder the water is, the more sodium or potassium ions are released from the resin and into the water.

Effect on Humans

For people on a low-sodium diet, the increase in sodium levels (for systems releasing sodium) in the water can be significant, especially when treating very hard water. A paper by Kansas State University gives an example: "A person who drinks two liters (2L) of softened, extremely hard water (assume 30 gpg) will consume about 480 mg more sodium (2L x 30 gpg x 8 mg/L/gpg = 480 mg), than if unsoftened water is consumed." This is a significant amount, as they state: "The American Heart Association (AHA) suggests that the 3 percent of the population who must follow a severe, salt-restricted diet should not consume more than 500 mg of sodium a day. AHA suggests that no more than 10 percent of this sodium intake should come from water. The draft guideline of 20 mg/L for water protects people who are most susceptible."

Effect on Environment

Over time the resins gradually lose their effectiveness and must be regenerated by passing a concentrated brine solution through them. Most of the salt used for regeneration gets flushed out of the system and may be released into the soil or sewer. This process can be damaging to the environment, especially in arid regions. Some jurisdictions prohibit such release and require users to dispose of the spent brine at an approved site or to use a commercial service company.

Most water softener manufacturers provide metered control valves to minimize the frequency of regeneration. It is also possible on most units to adjust the amount of salt used for each regeneration. Both of these steps are recommended to minimize the impact of water softeners on the environment.

In industrial scale water softening plants, the effluent flow from re-generation process can be very significant. Under certain conditions, such as when the effluent is discharged in admixture with domestic sewage, the calcium and magnesium salts may precipitate out as hardness scale on the inside of the discharge pipe. This can build up to such an extent so as to block the pipe as happened on a major industrial plant in Australia in the 1980s. I certainly would not want to be the person who had to clean that pipe!

To Sum Up

Although there are benefits to softening water, there are also consequences that must be taken into account, both human and environmental as discussed above. In my opinion, the benefits of softening probably outweigh the disadvantages as long as one is aware that it does directly effect the quality of the water and consequently the minerals it contains. People who must have strict control over their diet (particularly their sodium intake) need to be aware of this. Also, domestic water softening devices are very useful in preventing the hardness minerals which are removed causing hard water stains and limescale problems. They also do not have a significant impact on the environment compared to the much larger sized devices that are employed in industry.