Risks associated with drinking water from a well or private supply

Are you among the 20 per cent of people in Ireland who get their drinking water from a well or a private group scheme?

If so, you may not have the same peace of mind as the majority (80%) of the population who are connected to the mains water supply. That is not to say that mains water is 100% perfect, 100% of the time. However, the Environmental Protection Agency (EPA) consistently reports that the quality of the water in public supplies is better than that in wells/private supplies.

Mains water customers can rest assured that the water in their taps has been through a public treatment plant. They also know that their water quality is monitored by Irish Water, whose monitoring programme is, in turn, audited by the EPA.

In contrast, if your drinking water comes from your own private well, you are solely responsible for ensuring it’s safe to drink. Likewise, if you are supplied via a small private group scheme, that responsibility lies with the scheme manager.

So, am I legally obliged to get my water tested?

That depends. If your private water supply serves more than 50 people OR a public commercial premises such as a restaurant, creche or care home, then YES: you – or your scheme manager – is required by law to have the water source tested twice a year.

On the other hand, if your well is used only by family or household members – OR if your private supply serves less than 50 people AND you are not involved in a commercial/business activity, there is NO legal requirement to have the water tested.

Regardless, the EPA recommends that you have your water tested once a year for microbial contamination and once every three years for chemical contamination.

Why? What are the risks?

The agency estimates that between 15% and 30% of household wells are contaminated with a bacterium (bug) known as Escherichia coli (usually shortened to E. coli).

This bug can enter your well or private water supply as a result of cattle grazing nearby, run-off from slurry being spread on nearby land or runoff from a nearby septic tank that has been badly sited or is in some way defective.

E. coli can be found in the intestines of humans and some animals – as well as in their faeces/manure. In fact, since it is rarely found in the absence of faecal pollution,  its presence is a good indicator that your water source has been contaminated.

What does this mean? What are the risks of microbial contamination?

Drinking water contaminated with microbes can lead to acute infectious gastroenteritis. If a family member suffers from frequent stomach upsets, this could be a sign that they are drinking contaminated water.

Some householders become immune to low-levels of bacterial contamination. But the water may make visitors to their house ill, particularly children, the elderly, or those a weakened immune system. The HSE has produced a leaflet on the risks of illness from well water.

The rise of VTEC infection

Another concern relates to the rise of the so-called VTEC strain of E. coli (Verocytotoxigenic Escherichia coli). These bacteria produce a powerful toxin, causing severe abdominal cramps and diarrhoea. Usually patients recover within 5 to 10 days. But, in up to 10% of cases, the infection causes a complication known as haemolytic uraemic syndrome (or HUS), which can lead to kidney damage. The elderly and children under 5 years of age are particularly at risk of HUS. Further information from the HSE on private water supplies and VTEC is available here.

How should I go about having my water tested?

If you get your drinking water from a well or other private supply, the only way to tell it is safe is by having it tested at certified laboratory. In Ireland, the certification you should look for is the ISO standard 17025, which is accredited by INAB – the Irish National Accreditation Board.

As already mentioned, it is recommended that you test your water supplies for microbial contamination once a year and for chemical contamination once every three years.

However, you should have your supplies tested sooner, if you suspect they may have become contaminated since your last test – for instance, if the colour or odour seems off – or if a member of the household starts to have frequent stomach upsets.

Best time for a water test

Bear in mind that a test can only tell you about the quality of the water at the time of testing. The risk of microbial contamination is generally highest following a period of heavy rain or flooding. Therefore, this is best time to have your water analysed. If you know it is clear at times of greatest risk, then you can be more confident your well is performing satisfactorily all year-round.

For accurate results, you need to get your water sample to the laboratory within six hours of having taken it, and you must use sterile sample bottles. We supply these free of charge to customers, and our order form explains how to take your sample without introducing contamination from external sources. We hope you find this information useful.

This article has dealt only with microbial contamination. Watch out for our next article, which will look at chemical contamination, explaining possible sources and health impacts.