What makes water hard? What are the treatment options?
Before we cover hard water treatment, let’s define hard water. Hard water is just water that is high in mineral content. The most common minerals contributing to hard water are calcium and magnesium ions, from dissolved minerals such as limestone or dolomite in a water source. Contrast this to rainwater, which has very low mineral content, and distilled water, which in principal has no mineral content; water from these sources is termed soft water in comparison.
Because the ions dissolved in hard water have a positive charge, hard water is more alkaline (has a higher pH level) than soft water.
For household use the main issues with hard water are scaling and poor washing ability. The ability of a soap or detergent to clean is based in part on its ability to form suds. Water high in calcium and magnesium ions prevents soaps and detergents from sudsing – instead they tend to form a curd or scum that not only doesn’t clean well but is hard to get off. This curd or curd can gum up your hair, create an unpleasant film on your skin, or keep dirt embedded in the fibers of your laundry instead of washing it out.
Scaling is the other main issue with hard water. Scaling is the process where the dissolved minerals precipitate out of solution and build up layers of mineral deposits on solid surfaces. The calcium ions may combine with carbon dioxide and oxygen dissolved in the water to form calcium carbonate (CaCO3), or with sulphur and oxygen to form calcium sulfate, (CaSO4), while the magnesium combines with water to form magnesium hydroxide; both of these chemicals precipitate out of solution and build up on the walls of plumbing, reducing water flow and potentially damaging plumbing equipment such as pipes, hot water heaters, faucet assemblies and so on. We used to have terrible water pressure in our house; a contractor suggested I replace the first section of pipe from my indoor water meter, from 1/2″ to 3/4″ pipe, up to the first tee. When I cut out the old pipe, the build-up of scale inside that 6-foot section was so extensive I could not see any light when looking through it, even when I held the pipe up so that the far end was right in front of a light bulb!
Scale can also build up inside kettles and coffee makers, in toilets, and around sink taps if you let the sink get wet and then dry on its own, instead of wiping it dry (because as the water evaporates it leaves a deposit of scale behind).
A secondary problem with hard water in plumbing is that where the plumbing consists of two different metals – for example, an iron pipe for the water main intake and copper plumbing inside – the cations (positive ions) in the hard water can produce an electrical form of corrosion called galvanic corrosion, where one of the two metals corrodes very quickly.
I’ve lived in areas where hard water treatment was very commonly done, and have spent time in other areas where the water coming out of the tap was as soft as silk. My wife and I lived in north central Ohio for three years, in a town where the water supply was drawn from ground wells. The water there was very hard and we did all our laundry at the laundromat since they at least had a water softener to do the hard water treatment so that clothes would come clean. And we spend several weeks each year at my parents’ cottage, which draws its water from a northern Ontario lake. Because most smaller lakes in Ontario sit on granite bedrock, which has no acid buffering capacity, and because rain and snow are naturally acidic, the water in these lakes tends to be quite acidic or soft and hard water treatment is unheard of. Whereas it often took three or four squirts of dish soap to do a load of dishes in our hard water treatment area in Ohio, at my parents’ cottage we can scrub the pots and pans with a tiny squirt, and we put a mere teaspoon of detergent in the dishwasher to do a full load. And while washing one’s hair in hard water areas is always a sticky and unsatisfactory experience, at the cottage the tiniest amount of shampoo cleans one’s hair to a silky consistency.
Some areas with hard water have iron as one of the contributing minerals to hard water. While other dissolved minerals tend to be white in color and therefore have little effect on water color (only potentially affecting clarity), iron can give the water a brownish tint and an unpleasant taste. Our water in Ohio was especially hard and while it usually came out cloudy white, there were a few times when the taps dispensed something closer to the color of Coca Cola! But it’s unlikely this was because of excess iron in the water supply – more likely there was plumbing somewhere upstream of our house that had corroded and the iron oxides were leaking into the water supply from there.
Is it safe to drink hard water?
There are no real health risks associated with using hard water, and you should not consider hard water treatment if your only concern is your health. Some studies suggest that people who live in areas with hard water (and therefore presumably drink more of it) have a slightly lower risk of cardiovascular disease, while other studies have suggested that hard water can increase the incidence of childhood eczema, but the evidence for both these is thin, and in the childhood eczema case a trial of 336 children suffering from eczema found no correlation between water softener use and a reduction in their symptoms.
On the other hand, hard water treatment, while removing the dissolved calcium and magnesium and other minerals, replaces these ions with like-charged ions of sodium or potassium, which may be harmful to consume in your drinking or cooking water, especially to those suffering from hypertension.
Regions with hard water
Hard water treatment is common in many parts of the US, Canada, the UK and Australia. In the US and Canada, dry regions often have the hardest water since these regions tend to get their water supply from groundwater where mineral concentrations are higher, and in arid regions, where evaporation may over the years concentrate the mineral content of water, the water becomes ever harder. On the other hand, regions with large rivers and lakes or high volumes of rainfall – the Great Lakes, the Pacific Northwest – tend to have much softer water (at least when it is taken from those sources). Rain water has no dissolved minerals – it is, in a sense, distilled water – but it can become hard as it flows over rocks that are high in calcium or magnesium, so even water supplies coming from lakes or rivers can require hard water treatment if the waterway sits on such rocks.
How water softeners work
Hard water treatment – more typically called water softening – involves passing the hard water through a resin, or a medium of polystyrene beads, that has been impregnated with positively charged sodium or potassium ions. Through a process known as ion exchange, these sodium or potassium ions trade places with the calcium or magnesium ions and reduce the hardness of the water. Over time, the resin or bead medium becomes saturated with calcium and magnesium and runs out of sodium or potassium, so the unwanted ions must be discarded and new sodium or potassium ions must be brought in. This phase of hard water treatment is called regenereation.
The regeneration process involves washing the medium in a salt brine, either sodium chloride (rock salt – similar to table salt without the iodine) or potassium chloride. This salt brine is discarded once the medium is regenerated. In most hard water treatment systems the regeneration is done automatically, since keeping track of when to flush your water softener, and remembering to do it, and doing it correctly, are a nuisance to most homeowners. During regeneration the water supply may be limited or water in use may bypass the hard water treatment system briefly. Some more sophisiticated water softeners try to monitor home water use patterns and do the regeneration phase of hard water treatment at times when no use is predicted.
There are three main health or environmental concerns with hard water treatment:
- The increased sodium or potassium content of the water for drinking – especially for people suffering from hypertension or other health issues, you are better off drinking hard water than water softened with a sodium or potassium-based water softener.
- There is a potential environmental impact of dumping all that extra sodium chloride or potassium into the waste water treatment stream. While salts from water softeners do not appear to have much of an impact on effective sewage treatment or the operation of septic beds, there is a concern that wastewater recovery systems are affected by the increased levels of salts in treated waste water where water softeners are in use. Some areas in arid regions of the US and elsewhere have sought to ban water softeners for this reason.
- Water softeners, because they discard the brine, do increase water usage somewhat – by about 15 to 100 gallons a week. That’s the equivalent of flushing your toilet an extra 2 to 10 times a day, assuming you have a low flush toilet.
If you do decide to pursue hard water treatment by installing a water softener, I recommend:
- Not plumbing outside lines to it – for watering your garden you do not want to add extra sodium or potassium to the soil. The magnesium and calcium are beneficial to plants while the sodium especially may not be.
- Using a reverse osmosis under sink water filter for drinking water, or if the hard water is still drinkable, plumbing in a drinking water tap in your kitchen that bypasses the water softener, so that you are not drinking softened water, because of the health concerns over ingesting the sodium or potassium.