Parasites in Tap Water: What You Should Know

In the UK, we get clean and safe water to drink when we switch on the tap. Most times, there is often a fear of what could be present in that crystal-clear stream, such as parasites. However, the UK has some of the best water safety standards in the world.

However, it’s essential to learn how parasites can enter tap water, the danger they cause to human health, and how to prevent them and safeguard yourself and your family.

Parasites are small organisms that inhabit or live on another organism, which is referred to as a host, and they require the host to survive, usually at the cost of the host. In a context where water quality is compromised, these parasites may get into the system through contamination and present multiple risks to human health.

They are generally not seen by the naked eye and can exist in different water sources unless treated. The most prevalent and dangerous parasites in drinking water are:

• Cryptosporidium
• Giardia lamblia
• Entamoeba histolytica

These microorganisms are normally found in polluted water and may be harmful to humans, leading to gastrointestinal disorders.

In general, tap water in the UK is considered safe for drinking and is tightly controlled by Ofwat and the Drinking Water Inspectorate (DWI) . Nevertheless, in some cases, contamination may still occur as a result of the following:

• Damage to the pipes during construction or flooding.
• Runoff of agricultural water dripping into water sources.
• Malfunctions of water treatment facilities.

As a matter of fact, there have been instances of boil water notices in certain regions due to parasitic contamination. A prominent example was Lancashire in 2015 , where more than 300,000 households were instructed to boil their water after identifying Cryptosporidium.

This microscopic parasite is prevalent due to its resistance to chlorine and ability to endure a regular water treatment process. The symptoms include the following:

• Watery diarrhoea
• Stomach cramps
• Nausea
• Fever

It is especially harmful to people with compromised immunity, including older people, small children, or people undergoing chemotherapy.

Giardia is a parasite that causes a disease known as giardiasis , which is often transmitted by faecal contamination. The symptoms include the following:

• Diarrhoea
• Greasy stools
• Bloating
• Fatigue

It is less prevalent in the UK; however, it has posed some risk in areas with poor sanitation or places you visit while traveling abroad.

This parasite is more prevalent in developing nations and can lead to amoebic dysentery, but in the UK, infections are uncommon and usually associated with travel.

Parasites may sometimes find their way into the tap water in the UK via various contamination channels, but this is occasional. Rain or floods have the potential to saturate water treatment plants and sewage systems, exposing the risk of untreated contaminants in the supply. Farming practices are also a factor in which livestock wastes can be washed into rivers and reservoirs, supplying the municipal water supply.

Moreover, old or faulty pipes may enable parasites and other impurities to leak into what would otherwise be clean water lines. A plumbing system with cross-connections, in which the clean and dirty water lines are not properly connected, can also lead to backflow and the introduction of parasites to the tap water supply.

Related article: Can You Cook with Purified Water?

The UK water treatment plants pass through a sequence of stages to make the tap water safe to drink. Coagulation and sedimentation are the first steps and aid in the filtration of large particles in the water.

This is then followed by filtration that captures microorganisms like bacteria and parasites. Lastly, the majority of remaining pathogens are killed by disinfection, usually with chlorine or UV light.

In addition, chlorine-resistant parasites such as Cryptosporidium exist, which is why sophisticated filtration and UV treatment are essential in safeguarding the health of the populace.

Even when your local water company does its work, it never hurts to take additional measures, particularly when you live in a hazardous area or have a weakened immune system.

Seek NSF/ANSI Standard 53 or 58 certified filters to eliminate parasites. Reverse osmosis systems and specific countertop filters can successfully eliminate Cryptosporidium and Giardia.

Never disregard boil water notices issued by your water provider. Parasites can be killed by bringing the water to a rolling boil and leaving it there for 1 minute.

Contaminants may enter your water supply system at home because of old or broken pipes. Always check your system once a year.

When storing water as an emergency supply, store it in food-grade and clean containers and rotate your water every 6 months.

In case you have recently had symptoms of long-standing diarrhoea, stomach cramps, chronic fatigue, dehydration, or nausea and vomiting, and believe your tap water to be the problem, you should speak with your GP. These may be indicative of a potential parasitic infection. A simple stool test can be used to confirm the presence of parasites and ensure proper treatment.

It is very unlikely because of strict safety measures, but there might be some rare occurrences, particularly in the case of flooding or a treatment plant malfunction.

Most people do not need a filter, but in a high-risk environment or where you just want assurance, a filter is an option to remove any contaminant.

Your local water provider will issue a boil water notice when a contaminant is found. You can regularly get updates on the DWI site or website.

Yes, boiling water can kill most parasites for at least 1 minute.

Strictly go for a type that expressly states that it removes parasites or cysts, such as reverse osmosis or a ceramic water filter guide.

Parasite incidence is rare in tap water in the UK. It is always prudent to be knowledgeable and prepared, particularly when you have susceptible people at home. With a few preventive measures, you can still have safe, clean water right out of the tap.