UK legal limit: 200 mg/L. Find out what sodium is, its health effects, and how to check and reduce it in your tap water.
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Sodium is a naturally occurring mineral in water — it is present in virtually all water sources at varying concentrations. In most UK tap water, sodium levels are modest and represent a tiny fraction of daily dietary sodium intake. The UK legal limit for sodium in drinking water is 200 mg/L. This limit is set primarily on health grounds related to cardiovascular risk and is not routinely exceeded in UK tap water — most zones contain 10–60 mg/L sodium.
The main natural source of sodium in UK water is rock dissolution — sodium salts in sedimentary rock dissolve into groundwater. Coastal areas and areas with saline groundwater intrusion can have higher sodium levels. Ion exchange water softeners also increase sodium in softened water, which is relevant for households with home softeners — softened water should not be used for infant formula or by people on a sodium-restricted diet without checking the sodium level.
For the vast majority of people, sodium from tap water contributes negligibly to daily intake. The average UK adult consumes 8–10 g of salt (sodium chloride) per day, mostly from food. Even at the legal limit of 200 mg/L, 2 litres of drinking water would contribute only 400 mg sodium — less than 10% of typical daily intake. At typical UK concentrations of 20–40 mg/L, the contribution is less than 1%.
Sodium in tap water becomes relevant for specific groups: people on medically supervised very-low-sodium diets (below 500 mg/day), usually for severe heart failure or kidney disease; infants, for whom water used to prepare formula should have low sodium content (below 20 mg/L is recommended); and households with ion exchange water softeners, which replace calcium and magnesium with sodium. If you have a home softener, the softened water can contain 100–200 mg/L additional sodium and should not be used for drinking or cooking without a reverse osmosis point-of-use filter or bypass tap.
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For most people, sodium in tap water at typical UK concentrations (20–60 mg/L) is negligible compared to dietary sodium intake. Health concerns from sodium in water are only relevant for people on medically supervised very-low-sodium diets or for infant formula preparation.
The UK legal limit for sodium in drinking water is 200 mg/L. Most UK zones contain 10–60 mg/L, well below the limit.
Yes. Ion exchange water softeners replace calcium and magnesium (hardness) with sodium. Softened water can contain an additional 100–200 mg/L sodium. Softened water should not be used for infant formula or by people on sodium-restricted diets.
Not for most people. If you are on a medically supervised low-sodium diet or preparing infant formula, check your zone's sodium level and consider a reverse osmosis filter for drinking water.
Yes. Reverse osmosis removes 90–95% of dissolved sodium from tap water. Standard carbon filters and jug filters do not remove sodium.
Coastal areas with saline groundwater, areas served by softened water, and some zones in Eastern England (where groundwater has higher dissolved mineral content) tend to have higher sodium levels.