The silent contaminant: how nitrates get into your drinking water (and how to test for it)

The silent contaminant: how nitrates get into your drinking water (and how to test for it)

Most of us don’t think much about what’s in our drinking water, as long as it looks clear and tastes normal.

But that also means it’s easy to miss the things you can’t see. Some substances don’t affect taste, smell, or appearance at all—and the only way to know they’re there is to test for them.

Nitrates are one of these.

They’re one of the more commonly monitored contaminants in drinking water, particularly in agricultural areas.

Understanding how nitrates get into water—and how to test for them—can help you get a clearer picture of what’s actually in your supply.

What are nitrates, in simple terms?

Nitrates are naturally occurring compounds made up of nitrogen and oxygen. They’re found in soil, water, and many foods.

You’ve probably come across them before on food labels—particularly on products like bacon or cured meats, often labelled as “no nitrates added”.

In the environment, they’re part of a natural cycle. But human activity—especially agriculture—can increase the amount that ends up in drinking water.

How do nitrates get into drinking water?

Nitrates don’t usually enter water through a single source. Instead, they build up over time through a combination of environmental and human factors.

This often happens gradually, which is why it can go unnoticed.

The most common pathways include:

• Agricultural runoff: Fertilisers used on crops can seep into soil and be carried into groundwater or nearby rivers
• Animal waste: Livestock farming can contribute to nitrate levels when waste enters surrounding land and water systems
• Septic systems: Leaks or inefficiencies can allow nitrates to enter local groundwater supplies
• Natural processes: Organic matter breaking down in soil can also release nitrates

Once present, nitrates dissolve easily in water, making them difficult to remove without specialised treatment.

Why this often goes unnoticed

Nitrates are colourless, odourless, and tasteless.

That means there are no obvious indicators in your drinking water:

• No unusual taste
• No smell
• No visible change

Your water can appear completely normal, even when nitrate levels are elevated.

This is why they’re sometimes described as a “silent” contaminant—not because they’re rare, but because they’re difficult to detect without testing.

Why nitrate levels matter

Nitrates are a normal part of the environment, and they’re also found in many foods. So their presence in water isn’t unusual.

What matters is the level, and how consistently you’re exposed to it over time. Researchers continue to study how long-term nitrate exposure may affect health over many years.

At higher concentrations, nitrates can affect how oxygen is carried in the blood. This is why drinking water standards set limits and monitor levels closely.

Infants are the most sensitive, which is why guidance around preparing water for babies is more cautious—particularly because elevated nitrate exposure has historically been linked to “blue baby syndrome” (methemoglobinemia). For most healthy adults, regulated water supplies are generally considered safe—but levels can vary in certain situations, particularly with private water sources.

Where nitrate levels are more likely to vary

In the UK, public water supplies are regulated and regularly tested. For most households, this means nitrate levels are kept within defined limits.

But there are situations where levels can vary more, and where having your own understanding becomes more useful:

• Private water supplies (such as wells or boreholes)
• Homes in agricultural areas
• Properties relying on older infrastructure

In these cases, testing becomes particularly useful, as conditions can change over time.

How to test for nitrates in your water

Because nitrates aren’t visible, testing is the only reliable way to know whether they’re present.

There are a few practical options:

Method	What it’s good for	Things to keep in mind
Water quality report	Understanding general levels in your area	Doesn’t reflect your exact tap water
Home test kit	Quick, convenient check at home	Results may be less precise than lab testing
Laboratory testing	Accurate, detailed results	Takes more time and usually costs more

1. Check your local water quality report

Water suppliers and local authorities publish regular reports that include nitrate levels. This can give you a general sense of water quality in your area.

2. Use a home testing kit

Home kits can provide a quick indication of nitrate levels in your water. They’re particularly useful if you use a private water supply or want a more immediate snapshot.

When choosing a testing kit, look for one that specifically measures nitrates (sometimes listed as NO₃⁻). Many basic water test kits don’t include this by default, so it’s worth checking the details before buying.

Simple test strips can give a quick indication of nitrate levels, while more detailed kits or laboratory tests provide greater accuracy if you want a clearer picture.

3. Laboratory testing

For more detailed results, laboratory testing can provide a precise measurement of nitrate levels and other potential contaminants.

This is often the most accurate option, especially if you’re making decisions about long-term water quality.

What to do with the results

If testing shows that nitrates are present in your water, the next step is understanding what those numbers actually mean.

In the UK, drinking water standards for nitrates set a limit of 50 milligrams per litre (mg/L). Public water supplies are monitored to stay within this range.

As a general guide:

• Lower levels (well below 50 mg/L): typically considered within expected limits for regulated water supplies
• Approaching the limit: worth being aware of, particularly for households with infants or private water supplies
• Above the limit: usually means action should be taken to reduce exposure

If you’re preparing water for a baby, it’s worth being especially cautious with elevated nitrate levels, as infants are more sensitive.

If you’re using a private water source, or if levels are higher than expected, having this information gives you a clearer starting point for deciding what to do next.

Not all filtration systems are designed to address nitrates, so it helps to understand which types of filters can and can’t reduce nitrate levels.

A clearer way to think about it

Nitrates aren’t something most people can see or detect day to day.

But they are a normal part of how water interacts with the environment—and in some cases, they can build up in ways that aren’t immediately obvious.

Testing isn’t about expecting a problem. It’s simply a way to understand your water more clearly.

For many households, that clarity brings peace of mind. And if something does show up, you’ll know what to look into next—and how to respond with confidence.

Common questions about nitrates in drinking water

How do nitrates get into drinking water?
Nitrates typically enter water through agricultural runoff, animal waste, septic systems, and natural soil processes. Rainwater can carry them into groundwater and rivers, which may be used as drinking water sources.

Can you taste or smell nitrates in water?
No. Nitrates are colourless, odourless, and tasteless, which means they can be present without any noticeable change in your water.

How can I test my water for nitrates?
You can check your local water supplier’s report, use a home testing kit, or arrange laboratory testing for more precise results.

Are nitrates more common in certain areas?
Yes. Nitrate levels tend to be higher in agricultural areas or where private water supplies are used, as these are more exposed to environmental factors.

Do standard water filters remove nitrates?
Most standard filters are not designed to remove nitrates. More specialised systems, such as reverse osmosis or ion exchange filters, are typically required.