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Nitrate in drinking water

Does Reverse Osmosis Remove Nitrates? UK Guide

RO can reduce nitrate, but nitrate is not a problem to diagnose with a TDS pen. If it is your treatment target, measure it properly and verify the system's nitrate/nitrite claim.

Home Reverse Osmosis Does Reverse Osmosis Remove Nitrates? UK Guide

RO is a recognised nitrate-treatment option

Reverse osmosis can reduce nitrate and NSF/ANSI 58 includes an optional nitrate/nitrite reduction claim. DWI technical material also discusses RO as a membrane treatment relevant to nitrate removal.

Why private supplies deserve particular attention

Nitrate can be associated with agricultural land use and is an important parameter for wells, boreholes and springs. DWI guidance states that UKHSA and Public Health Wales do not recommend regular consumption of drinking water above 50 mg/L nitrate.

Do not infer nitrate from TDS

A conductivity reading cannot tell you how much nitrate is present. Laboratory analysis or appropriate regulated monitoring is required. If a private supply fails, involve the local authority and design treatment around the complete risk assessment rather than one number.

What to check on an RO product

Look for a model-specific nitrate/nitrite reduction claim, the conditions of the test, required replacement schedule and any feed-water limitations. A membrane that performs well when new can still be undermined by poor pressure, fouling, damage or neglected maintenance.

Mains-water households

Before buying a nitrate filter for regulated mains water, check the supplier's quality report. DWI specifically recommends doing this and notes that the report should reassure consumers that treatment is not normally required to make compliant mains water safe from parameters such as nitrate.

Sources and further reading

For factual claims that matter to health, regulation or product performance, we prefer primary and official sources. Useful references for this guide include:

Last reviewed: 6 October 2026. This guide is written for a UK audience. Always follow current supplier, regulator, manufacturer and healthcare advice where it applies.