Chemicals in drinking water 

Water ‘hardness’

Rain water is naturally ‘soft’, but once it falls and percolates through rock, it picks up natural ‘hardness’ minerals, such as calcium and magnesium. The hardness of your water will depend on your local geology.

Potential impacts: Water with total hardness or calcium carbonate (CaCO₃) content of 200 mg/l or higher will result in limescale formation on hot water systems, kettles, irons and other domestic appliances; ‘tide marks’ on basins, sinks, baths and toilets; and a scum on the surface of hot drinks, particularly tea.

Calcium and magnesium are both components of total harness. As a potentially positive impact, there is some evidence of a beneficial relationship between water hardness and cardiovascular health, possibly due to to the presence of calcium and magnesium.

A note about water softener systems: If you decide to install a water softener, it is  important to purchase from a reputable supplier and have it  installed by a qualified plumber.

The softening system should bypass the water supply to the kitchen tap used for drinking and cooking. This is important because most water softeners work by replacing the hardness with sodium. Too much sodium can be a problem for premature babies and people who are on a low sodium (low salt) diet.  Additionally, artificially softened water may also be aggressive to plumbing, causing leaching of copper and lead.

Other tests that indicate water acidity versus water hardness

At one end of the scale, alkalinity levels less than 100mg/l  indicate that water may  have a tendency to corrode plumbing, while, at the other end, alkalinity levels above 200mg/l may indicate the tendency for limescale deposits to form in pipes and on heating elements.

Langellier indices @15°C & 80°C are calculated from the combination of several tests. An index of ‘-1’ and lower tends to be associated with corrosive problems’ whereas an index of ‘+1’ and higher tends to be seen where there are limescale issues.

Ideally, you water should have parameters in between these limits, so that neither corrosion nor scaling are problems.

Lead

10 µg/l = Maximum Admissible Concentration

Lead rarely occurs naturally in groundwater. However, prior to the 1970s, some water pipes were made from lead. So, if you live in an older (pre -1970s) property, it is possible that part, or all, of your plumbing system is lead.

Impact: The maximum admissible concentration of lead in drinking water is very low at just 10 µg/l (mirco-grams per litre).  According to the World Health Organisation (WHO), lead is a general toxicant that accumulates in bone. It is toxic to both the central and peripheral nervous systems. Infants, children up to 6 years of age and pregnant women are the most susceptible to its health effects.

If lead piping is present in your water supply system, you should have it removed and replaced with new piping.

Nitrates

50 mg/l = Maximum Admissible Concentration

Nitrates in drinking water mostly originate from sources such as artificial agricultural fertilisers, animal slurry and, in some cases,  industrial waste discharge.

Impacts: Levels above 50 mg/l are considered dangerous for drinking – in particular for young children.  High levels of nitrate in drinking water may induce “blue baby” syndrome (methaemaglobinemia) in bottle-fed infants. The nitrate converts to nitrite, which reacts with blood haemoglobin, reducing the availability of the blood to hold oxygen.

For drinking purposes, removal of nitrate is required and can be carried out by the installation of a reverse osmosis (RO) system. Next week’s article will look at safe well design and remediation to avoid drinking water contamination by agricultural or industrial run-off.

Nitrites and ammonia

0.5 mg/l for nitrites and 0.30 mg/l for ammonia = Maximum Admissible Concentration

Nitrites and ammonia should only be present in drinking water  at very low levels.  Ammonia may be present in supplies as a result of run off from agricultural slurry, fertiliser or industrial waste.  It rapidly oxidises to nitrite (which principally exist as an intermediate) and, in turn, to nitrate.  Nitrites are even more potent than nitrates in the causation of methaemaglobinemia or ‘blue baby’ syndrome – as explained above.

Elevated levels of ammonia and nitrites are indicative of effluent contamination, and the source should be investigated and eliminated.

Iron and manganese

 0.2 mg/l for iron and 0.05 mg/l for manganese = Maximum Admissible  Concentration

Both iron and manganese are abundant metals in the Earth’s crust and are naturally present in drinking water.  The corrosion of steel and cast-iron water pipes can also cause iron to be present in drinking water.

Potential impacts: According to the World Health Organisation (WHO), these chemicals are not thought to associated with any negative health impacts. However, their presence in drinking water can cause severe discolouration.  Hence, under drinking water regulations, the maximum admissible concentrations are 0.2 mg/l for iron and 0.05 mg/l for manganese.

Higher levels of iron may result in water turning brown, becoming turbid or depositing solids on clothes washed in the water and food cooked using water. Even lower levels of manganese can cause staining. Manganese can also cause an objectionable taste, but this is not thought to be associated with any health risks (WHO).

Treatment systems, such as oxidation, can be used to remove to remove iron and manganese from your water supply.

Copper

2.0 mg/l = Maximum Admissible Concentration

Copper is essential for health, but at elevated levels, it can cause acute gastrointestinal effects. Under drinking water legislation, the maximum admissible concentration is 2.0 mg/l.

Copper is not usually found directly in groundwater, so if we find high levels in your sample, it has usually come from copper piping and hot water cylinders. This may occur in new homes as result of water lying stagnant in newly installed pipes. If this is the case, fully flushing the  system should result in lower copper levels.

On the other hand, blue deposits on taps, showers and toilet pans are indicator of more consistently high copper levels.

Water that is acidic (low in pH, see above) can cause leaching of copper from pipes and result in blue staining of sanitary fittings.

Zinc

1.0 mg/l = Maximum Admissible Concentration

In natural surface waters, the concentration of zinc is usually below 10 µg/litre, and in ground waters, 10– 40 µg/litre. In tap water, higher zinc concentrations that this can be the result of the leaching of zinc from piping and fittings.

Potential impacts: Although zinc is essential to good health, in drinking water, zinc levels above 1.0mg/l are undesirable. Water containing elevated zinc concentrations may form a greasy film when boiled and have an undesirable, astringent taste.  Considerably elevated zinc levels, several times the maximum admissible concentration,  can also result in stomach cramps, nausea and vomiting, and over a prolonged period, anaemia and damage to the pancreas.

Problematic leaching of zinc  can be addressed by addressing corrosion (pH) related issues.

Chloride

250 mg/l =  Maximum Admissible Concentration 

Chloride can originate from natural sources such as saltwater intrusion in coastal areas, but it can also be present in sewage and industrial effluents and may be an indicator of pollution from these sources. Next week’s article will look at protecting groundwater from contamination.

Conductivity

2500µS/cm @ 20°C = Maximum Admissible Concentration

Conductivity is a measure of the ability of water to conduct an electrical current. The maximum allowable conductivity level for drinking water is 2500µS/cm @ 20°C. A high conductivity level indicates the presence a high number of ions (electrically charged atoms or molecules), typically calcium ions, which are present in hard water. However, in coast areas, a conductivity level in excess of 800 µS/cm may indicate contamination from seawater.