Bacteria are found everywhere, including in our water systems. Yes, tap water can contain bacteria even when it looks, tastes, and smells completely normal. Bacterial contamination isn’t something you can detect with your senses, which is exactly why testing matters. Since testing for every type of germ isn’t practical, it’s important to focus on key bacteria that pose the highest risks.
Southern Scientific provides water testing services for harmful bacteria like Coliforms (including E. coli), Enterococci, and Legionella. In this article, we’ll explain why each type of bacteria is dangerous, what Irish regulations say about them, and why testing is so important.
Bacteria in Tap Water: Coliforms
What Are Coliforms: Coliform bacteria are a group of bacteria that live in soil, water, and the intestines of animals. Although not all coliforms are dangerous, their presence in drinking water can indicate that faeces may be contaminating it. Water containing faeces can carry harmful germs.
Health Risks of E. coli: E. coli is a type of coliform bacteria. Of the 5 coliform groups, only E. coli is generally not found growing in the environment. Therefore, E. coli is the best indicator of faecal pollution and the possible presence of pathogens. Certain strains of E. coli can make you very sick, causing stomach problems like diarrhoea, cramps, and vomiting. In severe cases, it can lead to urinary infections or even kidney damage.
The Legal Limit: Under Irish drinking water regulations (S.I. No. 278 of 2007), the legal limit for both Total Coliforms and E. coli in drinking water is zero per 100ml. Any detection is treated as an exceedance requiring investigation.
Why Test for Coliforms and E. coli: Testing for total coliforms and E. coli helps detect faecal contamination early. If found, immediate steps should be taken to clean and disinfect your water supply.
Irish data shows why this matters. In the EPA’s most recent report on private water supplies (2025), 14 private group schemes failed the E. coli standard, down from 24 in 2024, affecting 1,854 people. Small private supplies fared worse, with 67 supplies failing the standard, a 95% compliance rate. Even public supplies aren’t immune: the EPA’s 2025 report on public water found 24 supplies had failures linked to E. coli or Enterococci contamination, and almost 200,000 people were affected by boil water notices or other restrictions during the year.
At Southern Scientific, our Bacteria in Drinking Water Test measures Total Coliform and E. coli levels. With our Standard Drinking Water Test, you can carry out both microbiological and chemical testing.
Bacteria in Tap Water: Enterococci
What Are Enterococci: Enterococci are bacteria that live in the intestines of humans and animals. Like coliforms, they indicate faecal contamination in water. However, enterococci are more resistant than coliforms and can survive in water longer, making them a useful indicator of longer-term contamination issues.
Health Risks of Enterococci: Some types of enterococci, such as Enterococcus faecalis and Enterococcus faecium, can cause serious infections. These include urinary tract infections (UTIs) and heart infections (endocarditis). Enterococci contamination can even cause infections in the brain lining (meningitis).
The Legal Limit: As with coliforms, the legal limit for enterococci in drinking water is zero per 100ml under Irish regulations.
Why Test for Enterococci: Testing for enterococci can help identify long-term bacterial contamination. This bacteria signals the possible presence of other dangerous germs, making it important to test and fix any issues quickly. At Southern Scientific, we offer fast results, especially in emergency cases, so you can ensure your water is safe as soon as possible.
Bacteria in Tap Water: Legionellae
What Are Legionellae: Legionella is a type of bacterium found naturally in freshwater environments. However, when legionella grows in man-made water systems or air conditioners, it can cause serious health problems.
Health Risks of Legionellae: The most dangerous illness caused by Legionellae is Legionnaires’ disease, a type of pneumonia. People get this disease when they breathe in tiny water droplets from contaminated sources. Such sources may include showerheads, hot tubs, or air conditioning systems. Symptoms include fever, coughing, and chest pain. In severe cases, a Legionella infection can lead to respiratory failure and death.
Why Test for Legionellae: Legionella testing is critical in hotels, gyms, or hospitals to avoid disease. For example, in 2012, a Legionella outbreak linked to a hotel water fountain in Chicago resulted in 3 fatalities. Regular testing ensures that water is kept safe and such tragedies are avoided. At Southern Scientific, we offer Legionella testing, along with advice on maintaining water systems to prevent outbreaks.
Why Regular Testing for Bacteria Matters
Testing your water regularly is key to keeping you, your family, or your customers safe from harmful bacteria. As the EPA’s own data shows, even well-regulated Irish water supplies can experience bacterial contamination, and private supplies in particular carry higher risk. Whether you’re a homeowner or run a business, ensuring your water is free from Coliforms, Enterococci, and Legionellae is essential.
At Southern Scientific, we make testing easy and accurate. Here’s how it works:
- Order your test – Choose the test you need from our website.
- Collect your sample – Follow our instructions to collect your water sample.
- Get your results – We’ll send you clear, easy-to-understand results quickly.
Whether you need to test for Coliforms, Enterococci, or Legionellae, Southern Scientific offers the testing services you need to ensure your water is safe. With over 30 years of experience and INAB-accredited ISO 17025 testing, we deliver trusted, independently verified results. Get in touch today to find the right test for your water supply.
