What it is
Boron is a naturally occurring element found in rocks, soil and seawater. In water it is present as borate, which is colourless and tasteless.
Where it comes from
Natural boron in groundwater comes from boron-bearing minerals, and levels are higher near the coast where seawater influences the aquifer. Detergents and some industrial discharges are the main man-made sources, so boron can indicate that treated wastewater is reaching a supply.
Why it matters
Boron is needed in small amounts by plants and probably by people. The guideline is based on studies showing effects on development and reproduction at high long-term intakes. Typical UK levels are well below it. Boron is also important for irrigation and hydroponics, because many plants are sensitive to it.
What can be done about it
Boron is difficult to remove: ordinary filters and softeners do not take it out. Reverse osmosis removes a proportion, and specialist boron-selective resins remove more. Where boron indicates wastewater reaching the supply, the engineer will look for the source first.
Information last reviewed 5 October 2026 by Pozzani Pure Water.