Frequently Asked Questions

Q: “What Can I Do If One of My Drinking Water Test Results fails?”

A: If one or more of your Drinking Water Test parameters fails, please consult our guide below.

To ensure every household in Ireland has the cleanest drinking water possible, several parameters are included with our Standard Drinking Water Test.
To help you understand each of them, in this blog, we will write about the importance of monitoring all 12.

Chemical Testing

Since metals dissolve readily in acidic water, dissolved metals may be present in drinking water with a low pH level. Metals such as iron, manganese, copper, and lead can leach into drinking water from pipes or the local aquifer. Alkaline or “hard” water contains excess calcium and other minerals that cause the familiar scaly deposits on cookware and a bitter taste in coffee.
Ammonia in water can cause corrosion of copper pipes and fittings, causing stains on cloths and towels. The presence of Ammonium in water supplies indicates contamination from agricultural or industrial practices and sewage systems. Increased ammonium levels can also occur in areas with high amounts of agricultural activity.
Swallowing high amounts of nitrate and/or nitrite can cause a condition called methemoglobinemia. This condition affects the blood’s ability to carry oxygen. Infants younger than six months of age and pregnant women are more at risk of developing this condition. The presence of elevated Nitrite concentrations indicates a pollution event has occurred at the source.
Hard water is richer in minerals than soft water and tends to have a high content of calcium and magnesium because it has dissolved the compounds present in sedimentary rock. Hard water is safe to drink and is often considered healthy due to its high mineral content. However, there are several issues that arise due to the presence of hard water in the home, such as the presence of limescale on appliances such as showerheads, hot water heaters and dishwashers. Limescale build-up may cause a great deal of damage to appliances and can also affect the water pressure in your home’s plumbing system. Soap and shampoo may not lather up easily in the shower, and your hair and skin may appear dull or irritated. Hard water may also cause eczema and inflame other similar skin conditions.
The alkalinity test is a measure of the acid-neutralizing capacity of the water. The acidity of the water can erode tooth enamel and metal plumbing in your house. Continued drinking of acidic water can also cause acidosis.
Manganese exceedances in a drinking water supply may point to pollution of the source water, although some exceedances arise from naturally occurring high levels at the source. High levels of manganese have also been shown to cause ADHD and learning disabilities. Because of this, it is important to monitor the levels of manganese in drinking water to ensure that consumption does not increase to a point where toxic effects may occur.
Some older water mains are made from cast iron and may corrode to give the water a rust-coloured appearance which may not necessarily pose a health risk but would not be acceptable in terms of taste or appearance.
Total dissolved solids can affect your water quality, your health, your home plumbing system, and even daily tasks, such as cooking and cleaning. By measuring your water for TDS, you can better understand your water quality and how it affects your everyday life, allowing you to make an informed decision to solve your water quality problem and install the most effective filtration system for your home.
Scientists need to know the exact composition of the water we’re testing with to get accurate, repeatable results. Conductivity in freshwater systems is affected by the geology of the area through which the water flows. Streams that run through granite bedrock will have lower conductivity, while those that flow through limestone and clay soils will have higher values. High readings can also come from industrial pollution or run-off from roads. Extended dry periods and low flow conditions also contribute to higher conductivity readings.
The tendency of water to cause corrosion or scale in pipes and fittings is measured using a useful scale known as the Langelier Index.
The tendency of water to cause corrosion or scale in pipes and fittings is measured using a useful scale known as the Langelier Index.

Microbiological Testing

Certain strains, such as types of E. coli, can cause serious illnesses such as gastroenteritis, dysentery, and diarrhoea. Exceedances for E. coli can be due to a contamination incident either at a water source or through the water network, for example, at burst mains or at an illegal connection. Exceedances of E. coli can also occur due to a failure in the disinfection treatment process.
Coliform Bacteria should not be present in water that is disinfected, and their presence indicates that either disinfection has not been complete, that there is entry into the water mains in the distribution network or that the sampling point is contaminated. Their presence in drinking water indicates that disease-causing organisms could be in the water system.

What Do I do if my Result for Total Hardness Fails?

The presence of naturally occurring dissolved carbon dioxide, silica (from rocks, stone, sands) or humic acid (from peat) makes water acidic. Neutral waters have a pH of 7; acid waters have a pH lower than this. The pH measures potential for corrosion. When the pH of water is low it will be corrosive on metals. The lower the pH the greater the corrosion effects.

The Drinking Water Regulations, 2007 require that water used for human consumption be between 6.5 –

9.5 pH units.

The corrosion effect is measured by the Langelier Index test. A negative result says that the water will be corrosive to metals, See Table 1 below. Corrosive Water is not harmful to health.

Corrosive Characteristic

Langelier Index

Highly aggressive

< -2.0

Moderately aggressive

-2.0 to 0.0

Non aggressive


Table 1: Corrosive characteristics of water as indicated by the Langelier Index

Problems associated with acid water and corrosion:

  • Damage to metal components of water system, piping, tank, water heater, and fixtures.

  • Presence of blue/green stains, leaks and perforations.

  • Toxic metals contaminating drinking water.


  1. The water can be treated by passing it though a filter bed contained in an enclosed tank. The filter bed contains a material called dolomite. This is a natural stone containing calcium and magnesium salts. A small amount of dolomite dissolves into the water causing the pH to become balanced near neutral (7.0 pH).

  1. Filter materials other than dolomite can be used such as limestone, and soda ash.

  1. A liquid solution of an alkaline material such as soda ash or caustic soda can be dosed into the water in very small quantities using a liquid dosing pump. This system is more expensive than 1 or 2 above.


Ammonia, Nitrate and Nitrate are all forms of Nitrogen that may occur in drinking water as a result of degradation of waste from human and animal origin.

When any of these parameters are present above the Drinking Water Regulations, 2007, limits given in your analysis report there is a high probability that their origin is from sewage or industrial contamination. In this circumstance it is necessary to find the source of the contamination, prior to deciding whether or not to treat the water.

Contamination of any water supply can occur either on a once off basis, could be intermittent or could be ongoing.

In the case of surface waters supplies such as a river or stream the contaminating source may be obvious. There could be a surface drain or seepage from a domestic sewer system, a farmyard or any industrial sources.

Upland streams may be contaminated by dead animals such as sheep etc., and lowland streams may be contaminated by land run off. Check for recent fertilizer spreading in the area. Bag fertilizer as well as slurry can give elevated Nitrate and Ammonia concentrations in source waters if heavy rainfall follows spreading.

Groundwater from bored or shallow wells can be contaminated discretely through bedrock movement of water.

If nitrogen compounds are present at elevated concentrations in the water it is possible that E- coli bacteria will contaminate the water as well. Make sure that you do a test for coliforms and E-coli bacteria on a few occasions to ensure that the water is hygienically safe to drink.


A surface water contaminating source may be identified by inspection. Firstly try to establish if the contamination source is coming from within your own site or land. Also try to determine if the pollutant is entering the well from the immediate surrounding land through seepage. All pollutant sources originate overground but may be difficult to identify as the source might be covered, e.g. cracks or leaks in silage pits, slurry tanks or septic tanks.

If not, it may be necessary to engage an environmental scientist to do an investigation of local sources of pollution.

E-Coli and coliforms are bacteria that originate in human and animal waste. Some coliform bacteria can grow in soil; therefore the presence of coliforms with the absence of E-coli is not as serious as the presence of both in the sample together.

If there is one or more E-coli present in a sample, the supply cannot be consumed without sterilization or boiling.


If the tests carried out on this sample show that you have a problem with your drinking water due to the presence of bacteria, these bacteria will need to be eliminated before the water is safe to drink. You may need to install a water treatment system, which will remove these bacteria. However the following steps should be carried out before installing such a system because of the cost involved.

Step 1

Ensure that the well is covered and protected. Check the area surrounding the well for possible sources of contamination such as: surface water seeping into the well during or after rain, the existence of silage pit, dungstead or decaying vegetation near to the well, the close proximity of a stream, pond or drain.

Step 2

Make necessary changes to prevent these possible sources of contamination.

Step 3

Disinfect the well. Disinfect the well using a chloros solution. This can be purchased from your Co-op Store or from most hardware shops. Add a cupful of chloros into the well once a week for two weeks. Ensure water is flushed through well thoroughly to rinse out chloros.

Step 4

Re-Sample: The well should then be re-sampled one week later, after step three above, to test for bacteria and chlorine.

The sample passes the re-test

If the retest shows that sample is now free from bacteria the water is safe to drink. It is advisable however that a re-test be carried out at a later stage thereafter, to ensure that contamination has not returned.

Thesample fails the re-test

If the sample fails the re-test it will be necessary to install a treatment system to continuously disinfect the water. There are two systems from which you can choose:

A. Chlorinating System or B Ultra Violet Lamp System

  1. Chlorinating

If the water supply has both chemical and bacterial problems then the chlorinating system is worth considering. A holding tank has to be installed together with a chlorine-dosing pump. Chlorine has the disadvantage of being fairly corrosive, with pumps lasting anywhere between two to eight years.

About one third of all well waters have elevated levels of iron. A similar metal to iron and equally harmless to health is manganese. Small amounts of iron and manganese, less than 0.5 parts per million, may never be tasted or seen in the water. However the addition of chlorine to water with elevated iron and manganese down to 0.10 parts per million will result in a brown/yellow colour and floc developing, due to the presence of the iron and manganese. This floc settles to the base of a holding tank, and can be removed periodically – it is not harmful. Chlorine is normally purchased as chloros, which is a solution containing 12% active chlorine.

It is not advisable to chlorinate water which is coloured (>50 Pt-Co) because chlorine reacts with colour to produce cancer causing chemicals. For this reason a colour test should be carried out on the supply on a number of occasions prior to the instillation of a chlorine dosing unit to ensure that colour is not elevated. If colour is consistently greater than 50 colour units (Pt-Co) you must consider removing the colour, please refer to the information sheet on colour in water. Alternatively install a UV Sterilizing unit as described in option B below.

  1. Ultra Violet Lamp System

The ultra violet lamp system is easy to install and requires little maintenance other than a lamp change every six to twelve months. If surface water from a river or lake is used, a sediment filter will also need to be installed. This system is only suitable for water with bacterial contamination, however, and will not eliminate any chemical problems. For this reason it is recommended to seek advice before choosing a system to ensure that the system best suited to your needs is installed.

Water is usually coloured by the following:

  1. Organic substances that are picked up from degraded vegetation (e.g. leaves, wood)

  2. Organic substances that are leached from peat.

  3. Elevated levels of iron and manganese in the water.

Coloured water is made less drinkable by the presence of suspended particles, as can happen to river water during flood conditions.

Colour causing substances do not pose a health risk. The drinking water regulations, 2007, has no limit for colour except to require that the water is “acceptable to consumer and has no abnormal change” above normal. The original drinking water Regulations, 1978, had a limit of 50 Pt-Co. This is a useful guide to deciding whether the water is of satisfactory quality.

The presence of colour in water above 50 Pt-Co is not desirable if chlorine disinfection is used. Colour forming substances react with chlorine to produce tri-halomethanes, some of which are cancer-causing chemicals. It is better to use U.V. sterilisation in preference to chlorine to remove bacteria from the water if colour is present.


  1. A carbon filter placed under the sink will remove colour efficiently for the single house supply. Some units come with a hot-water back flush system. The carbon filter cartridge is replaced periodically.

  2. For large supplies of water such as group schemes, hotels etc. Colour can be removed by chemical flocculation with aluminium sulphate. There will be need for pH correction using soda ash or lime prior to pumping into the supply system. This type of system requires a lot of control because the dosing must match the variation in colour otherwise, excess aluminium sulphate will exist in the supply. Aluminium is an undesirable element in drinking water above 50µg/L

Hardness occurs naturally in water when it comes into contact with limestone. It gives water its taste. Health studies show that when water is hard (high in lime), heart disease is lessened.

The alkalinity test on water relates to hardness. Both results will be either high or low together. One test result confirms the other, in respect to the level of lime in the water.

The hardness classification of the water can be determined from the table below:

(Match the result for Hardness.from your sample analysis report with the values given in the table below.)


Result; mg/L CaCO3


Up to 50

Moderately Soft

51 I 00

Slightly Hard

IO I 150

Moderately Hard

151 250


231 350

Excessively Hard

Over 350

If the water is Moderately Hard, Hard or Excessively hard then a water softener is required.

Problems associated with hard water or lime are:

  • Scaling of pipes, boiler and immersion heater

  • Scaling of kettles and other domestic appliances

  • Unsightly scaling in kitchens and bathrooms

  • Blocked taps and shower heads

  • Increased fuel bills due to inefficient transfer of heat through pipework.

  • Destroys the lather in soap


Water Softener:

A water softener is a filter that removes the calcium and magnesium salts that cause lime scale. Usually all of the water for the household use is passed through the softener filter. The softener accumulates the lime scale during use. At night the softener filter is back flushed to remove the lime. This involves drawing a cleaning solution of salt and water through the system by a control valve.

A water softener will prolong the lifetime of domestic appliances, kettles, washing machines etc., and decrease fuel bills.

Hydrocarbons are substances derived from petroleum, oil grease and coal tar. Common types occurring in water are petrol, diesel and kerosene. Other hydrocarbons include polyaromatic hydrocarbons such as benzo pyrene which comes from tar and creosote. Individual chemicals e.g. Benzene is a chemical occurring in petrol. Toluene ethylbenzene and xylene are solvents in paints and adhesives.

Hydrocarbons give an unpleasant taste and odour to a drinking water at very low concentrations. Except for poly aromatic hydrocarbons and benzene other hydrocarbons are not harmful to health in the concentration likely to occur in water.

Limits for Hydrocarbons in water.

There is no limit for generic (petrol, diesel, kerosene) hydrocarbons in the current drinking water regulation [S.I. No 278 of 2007, European Communities {Drinking Water} No. 2, Regulation 2007].

A useful guide limit for generic hydrocarbons in drinking water can be taken from the surface water regulation (1989) where water that is class A standard should have less than 0.01 mg/L (or 10 µg/L) of hydrocarbons. This limit may be used as a useful guide to ensuring that a contaminated supply is fit to drink after it has been removed from the water system.

Specific Hydrocarbons have limits:

Polyaromatic Hydrocarbons (PAH) Limit is 0.0001 mg/L

Benzene Limit is 0.001 mg/L

Benzo(a)pyrene Limit is 0.00001 mg/L

The above compounds are cancer causing chemicals, hence the very strict limits imposed on them. Detection of the presence of petroleum type hydrocarbons in water.

Odour and taste will be detected at concentration above 1 mg/L. A film may be seen on the surface of the water or attached to the inside of vessels and pipe work. Analysis is required to identify the type of hydrocarbons present and to distinguish petrol, diesel and kerosene. This information will be useful in finding the source of contamination.


  1. Eliminate the source of contamination.

  2. Flush the pipe work and tanks with detergent containing warm water.

  3. If a well has been contaminated badly, it may require special treatment to clean it our properly. Repeated flushing will gradually remove the contamination once the contributing source has been eliminated. A special chemical can be pumped into the well that degrades hydrocarbons into harmless chemicals. This treatment is called bio-remediation.

The limit for lron according to the Drinking water Regulations 2014, is 0.20 mg/L (i.e. 200 µg/L)

Iron is not harmful to health

Problems associated with Iron in water.

  • Discolouration

Dissolved iron is not visible in water, however, when it comes into contact with air, (in storage tanks, when boiled in washing machines, etc.) it will oxidise (become rusty) and then it discolours the water, which in turn, discolours laundry, clothes, baths, toilets, sinks, kitchen ware, drinks – tea, whiskey, etc.

  • Blockages

As the iron oxidises it precipitates and builds up inside tanks, copper cylinders, boilers, pipe work, central heating systems, etc. It will also clog up devices such as the small filter in washing machines.

  • Bad Taste

The oxidised iron in the water causes an unpleasant taste in drinking water, tea and other drink.

  • Associated Problems

When there is iron dissolved in water, in approximately 80% of all cases, there are other problem constituents also in the water. There may be Lime (scale), Manganese (black flecks), Hydrogen Sulphide (rotten egg smell), suspended solids or lron Bacteria, or the water could be acidic (corrosive).


Iron can be removed by installing a filter. The Iron Filter will also remove Manganese. The filter consists of a tall slim tank, typically 4 feet high. The tank contains a filter bed made from, different materials. The choice of materials for the filter depends on the chemistry of your water. When water passes through the filter, iron is removed by attaching to the particles on the filter material. At night-time a back wash comes into op6ration where a cleaning liquid held in a drum beside the filter tank is passed though the filter. This removes the iron and any accompanying impurities and washes them to waste. This cycle repeats itself every couple of days.

The limit for Manganese according to the Drinking Water Regulations 2014, is 0.05 mg/L (i.e. 50 µg/L). Manganese is not harmful to health at the concentrations in which it occurs in water (up to 3 mg/L). It is an essential element for human and animal nutrition, but water is not a common source for this metal.

Problems associated with Manganese in water.

  • Manganese can give water an unpleasant taste at concentrations greater than 1.0 mg/L

  • It can cause discolouration of the water especially when sterilising fluids are added e.g. chlorine

  • Manganese causes discolouration of cloths and utensils at concentrations greater than 0.1 mg/L

  • Manganese causes small black particles to appear in the water giving the water a dirty appearance. These particles can block valves and pipes.


Manganese can be removed from water by installation of a filter. The filter used will also remove iron if present. The filter consists of a tall slim tank, typically 4 feet high. The tank contains a filter bed made from, different materials. The choice of materials for the filter depends on the chemistry of your water. When water passes through the filter, manganese is removed by attaching to the particles on the filter material. At night-time a back flush comes into operation where a cleaning liquid held in a drum beside the filter tank is passed though the filter. This removes the manganese and any accompanying impurities and washes them to waste. This cycle repeats itself every couple of days.

Sulphide gives water a rotten egg smell. It occurs as a result of:

  1. The decomposition of organic matter in water

  2. The decomposition of organic matter in waste and

  3. The bacterial conversion of sulphate, a natural mineral in water.

The natural mineral pyrites (iron sulphide) occurs in some well waters. If the water is acidic (pH less that 7) the sulphide exists as hydrogen sulphide, which gives the rotten egg smell.

There is no limit for sulphide in water but levels above 5 µg/L will give foul odours. Its presence is usually related to iron. Removal of iron will automatically remove the sulphide. If a foul odour exists and you also have iron present in the water you should ensure that the water is free from coliforms prior to deciding to treat the water for iron and sulphide only.

If a foul odour exists and you know that iron is not present or a test shows no iron present you are strongly advised to do a coliforms test, because the sulphide could be coming from waste.


  1. If the water has an elevated iron (not necessarily above the limit of 0.20 mg/L) along with sulphide; installation of an iron filter will also remove sulphide. Green sand, manganese or a birm, are good filter media for iron and sulphide.

  2. If the water has coliforms and sulphide present, chlorine disinfection is the preferred treatment option.

  3. If the water has a low iron (<0.10 mg/L) and is free of coliforms, aeration of the water in a holding tank will eliminate sulphide. Aeration is achieved by instillation of a small air pump delivering <1 L/min, such that its delivery pipe outlet is placed near the base of the tank to ensure efficient contact between the air and the water.

These are related parameters that are measured as the ions in solution that are capable of conducting an electric current. The more ions present in water the greater the electrical conductivity of that water. Ions are salts, both naturally present and present as contamination such as sodium and chloride coming from salt.

A high conductivity; greater than 1000µS/cm corresponding to a dissolved solids content ofabout500mg/Lshowsthatthereareextraneousdissolvedsaltsinthewater.Limywaterwillgive ahighTDS but usuallynot greater than500mg/L.

AhighTDSis an indication ofthe presenceof salts. Potassiumand sodiumsalts can occur fromcontaminationofwatersourcebywastewater,fromanindustrialsourceor fromseawater.

Test the water for sodium, potassium and chloride if you have not done so. If any of these three tests exceed the limits stated in the drinking water regulations, 2007 you must seek to identify their source firstly.


All salts are eliminated from water using ion-exchange filters. It is better to eliminate these rather than use a treatment solution.

Wells near the coast may suffer ingress from seawater. It is difficult to eliminate these sources of contamination; therefore a treatment unit may be the only option available.

An ion exchange filter consists of a tall slim tank, typically 3 to 4 feet high. The tank will be filled with a resin. When water passes through the resin, salts are trapped on the resin and the clean water passes on into the supply. The resin will eventually become saturated with the accumulated salt. It must be replaced with fresh resin. The life span of a tank full of resin depends on the salt content of the water and the volume of water used.

The limit for turbidity in drinking water is 1 NTU. Turbidity occurs in water as a result of:

  1. Turbidity in water is suspended particles that will not settle out when the water is still. These particles of solid occur from a variety of sources that depend on the type of water, i.e. well water or surface water.

    1. Well water particulates usually come from silt or silt/clay. This is common in a freshly dug well but clears away after sustained pumping for a few days.

    2. Intermittent turbidity in well water hints to a problem of ingress of surface water to the borehole. If it occurs during or after heavy rainfall it is conclusive proof of surface water ingress. In this instance other tests may also fail particularly the coliform and nitrogen tests.

  2. The presence of iron in well water will give rise to turbidity that has a yellow brown colour Test for iron.

  3. The presence of manganese in water gives rise to turbidity with black or brown particles Test for manganese.

  4. Some piped waters (public supplies) will have high turbidity as a result of debris and iron floc dislodging from the inside of pipework.

  5. When the water comes from a stream or lake turbidity arises from silt/clay particles, degraded vegetation, waste, algal or bacteria growths.

A high turbidity should always require a test for coliforms and nitrogen compounds so as to eliminate the possibility of contamination by waste matter. Also do a test for colour because if the water is coloured as well as turbid the treatment option for the elimination of bacteria involving chlorine cannot be used.


  1. If the high turbidity is accompanied by the presence of coliforms disinfection with chlorine or UV is required with pre-filtration.

  2. If the high turbidity is accompanied by a yellow/brown colour, test for iron and treat accordingly

  3. If the high turbidity is accompanied by a black/brown colour, test for manganese and treat accordingly

  4. If the water has a high turbidity and other test parameters are satisfactory, filtration will suffice. A 5-micron filter will give good quality water. A 20-micron filter will give moderate quality water.


Now hopefully, you understand more about the parameters we test for in our Standard Drinking Water test. Learn more about our Standard Drinking Water Test Here:
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