Understanding Your Water Report

This information is intended to help you interpret the results of commonly recommended analyses of water. Some of these tests are important because they deal with health-related contaminants; the other tests will tell you about important characteristics of your water, such as how hard or corrosive it is.

The most important result in terms of the hardness of your water is the Total Hardness as CaCO3 result.


Alkalinity is a measure of water’s capacity to neutralise acids and is important during softening. Alkalinity is the result of the presence of bicarbonates, carbonates, and hydroxides of calcium, magnesium, and sodium.  Alkalinity and total hardness are usually nearly equal in concentration (when they are both reported in mg/l CaCO3) because they form from the same minerals. If alkalinity is much greater than total hardness, it may indicate that your water has passed through a water softener. If alkalinity is much less than total hardness it may indicate elevated levels of chloride, nitrate or sulphate. Water with low levels of alkalinity (less than 150 mg/l) is more likely to be corrosive. High alkalinity water (greater than 150 mg/l) may contribute to scaling.


Ammonia is used in fertiliser and animal feed production as well as in the manufacture of plastics, paper, rubber, etc and is found naturally in water.  Levels higher than around 0.1 mg/l usually indicate contaminated water.


Boron is released into air, water, or soil when soils and rocks naturally weather. According to the World Health Organization, the health-based guideline for boron level in drinking water is 2.4 mg/l.


Hard water is water that contains dissolved minerals, predominantly calcium & magnesium. Water containing calcium carbonate at concentrations below 100 mg/l is generally considered as soft; 101–200 mg/l, moderately hard; 201–275 mg/l, hard; and more than 275 mg/l, very hard.


Carbonate hardness is a measure of the water hardness caused by the presence of carbonate (CO2-3) and bicarbonate (HCO3) anions.  Produces alkalinity and forms scale in hot water facilities as a result of hardness in combination with calcium and magnesium.


Chlorides are usually associated with the salt content and the amount of dissolved minerals in water. Levels less than 10 mg/l are desirable and the recommended limit for chlorides is 250 mg/l. Levels above this may cause a salty taste and corrosion of some metals.


Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulphate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminium cations (ions that carry a positive charge).  A normal conductivity value is roughly twice the total hardness in unsoftened water samples. If conductivity is much greater than two times the hardness, it may indicate the presence of other ions such as chloride, nitrate, or sulphate.


Copper is a metal that exists naturally in water, soil, plants, and animals. Copper can end up in water supplies as a result of several different industrial processes, including mining, farming, and factory work. Copper pipes can corrode, releasing more copper into the water. The maximum allowable level of copper in water set by the World Health Organisation is 2 mg/l.

Dissolved Silicon

Water passing through or over the earth dissolves silica from sands, rocks and minerals. The silica content in natural waters is commonly in the 5 to 25 mg/l range.


Iron is a metal widely found in rocks and soils. Water with iron may look clear at first, however upon exposure to air the iron is oxidised to form orange/red insoluble particles. Iron levels above 0.3 mg/l can result in light red/brown colour stains on plumbing fixtures and laundry and can cause undesirable tastes.


Hard water is water that contains dissolved minerals, predominantly calcium & magnesium. A magnesium level of less than 40 mg/l is recommended to minimise scaling in water systems.


Manganese is a metal widely found in rocks and soils. At levels exceeding 0.05 mg/l manganese stains plumbing fixtures and laundry a dark brown colour and causes undesirable tastes. Its presence in water may lead to microbial growths in the pipe system. Manganese is essentially nontoxic at levels normally found and only causes health problems at levels where there is a very undesirable taste.

Nitrite/ Nitrates

Nitrates/ Nitrites /Ammonia are found in nature from many sources, primarily from fertilisers and effluents. It is advised that drinking water is < 10 mg/l Nitrate or 1 mg/l Nitrite.


pH is a measure of the intensity of the acidity/alkalinity of water on a scale of 0-14 with 7 being neutral. Low pH (<6.5) results may lead to corrosion of metal pipes and surfaces and a green/blue off colour on ceramic tiles and sinks.


Phosphorus is naturally present in most waters. It is also added to 95 per cent of UK drinking waters in order to reduce the amount of lead that can dissolve into our water. This dosing of the water leads to concentrations of about 1 mg/l phosphorus in UK drinking water.


Although concentrations of potassium normally found in drinking water are generally low and do not pose health concerns, the high solubility of potassium chloride and its use in treatment devices such as water softeners can lead to significantly increased exposure. A guideline figure for concentration of potassium in drinking water in the UK is 2.5 mg/l.


Instead of having higher levels of calcium and magnesium, soft water tends to have higher concentrations of sodium, or salt.  Sodium salts (e.g. sodium chloride) are found in virtually all food (the main source of daily exposure) and drinking water. Although concentrations of sodium in potable water are typically less than 20 mg/l, they can greatly exceed this in some countries. It should be noted that some water softeners can add significantly to the sodium content of drinking water.

Sulphate as SO4

Sulphate can be present in water due to man-made and natural processes, but it is often added during the water treatment processing as aluminium sulphate. Sulphate increases the conductivity of water and so enhances corrosion processes which can then lead to a higher concentration of metals in the water. High levels of sulphate affect the taste of the water. The European Union Drinking Water Directive (1998) states a guideline maximum value of 250 mg/l.

Total Hardness as CaCO3

Hardness as CaCO3 is the concentration of calcium and magnesium ions expressed as equivalents of calcium carbonate. This is considered the best way of measuring hardness in water. Measurements are in mg/l.


Although levels of zinc in surface water and groundwater normally do not exceed 0.01 and 0.05 mg/l, respectively, concentrations in tap water can be much higher as a result of dissolution of zinc from pipes.  Concentrations of zinc are likely to be greatest in water that sits in the plumbing system for extended periods of time. If zinc is elevated, letting the water run for 1-2 minutes prior to use should significantly reduce concentrations.  Concentrations greater than 3 mg/l can be detrimental to the appearance of the water, with a greasy surface film developing and an unpleasant metallic or astringent taste.  Water containing more than 5 mg/l may also have a chalky appearance.

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