Nitrate in Drinking Water UK: Sources, Risks & Limits

What is Nitrate in Drinking Water?

Nitrate (NO₃) is a naturally occurring compound of nitrogen and oxygen. While small amounts are normal in water, elevated levels in UK drinking water are primarily caused by agricultural runoff — nitrogen-based fertilisers washing off farmland into rivers and percolating into underground aquifers.

Nitrate is one of the most common water quality concerns in rural England, particularly in regions with intensive arable farming.

UK Legal Limits

The Drinking Water Inspectorate sets the maximum at 50 mg/l. Typical UK tap water contains 5-30 mg/l, though agricultural areas may see levels closer to the limit, particularly after heavy rainfall when fertiliser washes into water sources.

Health Risks

Infants under 6 months: The primary concern. Nitrate converts to nitrite in the digestive system, which can reduce the blood's ability to carry oxygen — a condition called methaemoglobinaemia or "blue baby syndrome." This is why the legal limit exists. It is extremely rare in the UK.

Adults: The evidence on health effects for adults is less clear. Some studies suggest a link between long-term nitrate exposure and certain cancers, particularly stomach cancer, but the research is not conclusive. The WHO considers the 50 mg/l limit protective for all age groups.

Where is Nitrate Highest in the UK?

The highest nitrate levels tend to be in:

East Anglia (Anglian Water) — intensive arable farming on chalk aquifers
East Midlands (Severn Trent) — mixed farming areas
Lincolnshire and Yorkshire — groundwater-fed supplies in farming regions

Water companies in these areas invest heavily in nitrate removal plants and blending strategies to keep levels within limits.

How to Reduce Nitrate

Reverse osmosis: The most effective home treatment, removing 90-95% of nitrate. Requires installation under the kitchen sink.

Ion exchange filters: Specifically designed for nitrate removal. Not the same as standard water softeners.

Note: Boiling water does NOT reduce nitrate. Standard carbon filters and jug filters do NOT remove nitrate.

Check Your Water's Nitrate Level

Enter your postcode on WaterGrade to see the nitrate measurement for your area, sourced directly from your water company's reports.

Frequently Asked Questions

What causes high nitrate in drinking water?

Nitrate in UK drinking water comes primarily from agricultural fertilisers that wash into rivers and seep into groundwater. Sewage discharges and natural decomposition of organic matter also contribute. Areas with intensive arable farming, particularly in East Anglia and the East Midlands, tend to have the highest nitrate levels.

What is the legal limit for nitrate in UK water?

The UK legal limit for nitrate in drinking water is 50 milligrams per litre (50 mg/l), matching the EU Drinking Water Directive and WHO guidelines. Most UK tap water contains between 5 and 30 mg/l, well within the legal limit.

Is nitrate in water dangerous for babies?

High nitrate levels can be dangerous for babies under 6 months old. In the body, nitrate converts to nitrite, which can interfere with the blood's ability to carry oxygen, causing a condition called methaemoglobinaemia (blue baby syndrome). This is extremely rare in the UK because water supplies are monitored to stay within legal limits.

Can I remove nitrate from tap water?

Standard jug filters do not remove nitrate. You need either a reverse osmosis system or an ion exchange filter specifically designed for nitrate removal. Boiling water does not reduce nitrate — it actually concentrates it as water evaporates.