Orange stains in the toilet, brown water from the tap, black specks in the sink or laundry that comes out discoloured: these are the classic signs of iron and manganese in your water. Both metals occur naturally in rock and groundwater, so they are especially common in borehole and well supplies. They are rarely an immediate health risk at typical levels, but they stain, taste metallic, block filters and stop UV disinfection working.

At a glance

  • UK limits: iron 200 µg/l; manganese 50 µg/l
  • Most at risk: boreholes and wells; occasionally mains water after pipe disturbance
  • Signs: orange or brown staining (iron), black or dark brown deposits (manganese), metallic taste
  • Fix: iron and manganese reduction filters

Why is my water brown, orange or black?

Deep underground, where there is little oxygen, iron and manganese stay dissolved and the water comes out of the borehole perfectly clear. Once that water meets air, in a tank, a toilet cistern or a glass left standing, the metals oxidise and turn into tiny solid particles. That is why water can look clean straight from the tap and then turn orange, brown or black after a few minutes.

  • Iron gives orange, red-brown or yellow staining on sanitaryware, tiles and laundry, and a metallic or rusty taste.
  • Manganese gives black or dark brown specks and staining, and can build up as a black slime in pipes and cisterns.
  • Iron bacteria sometimes feed on dissolved iron, leaving a reddish, slimy film in cisterns and an unpleasant swampy smell.

Brown water on a mains supply

If you are on mains water and the water suddenly runs brown, the most common cause is sediment from old iron water mains being stirred up by a burst, repair or change in flow. Run the cold kitchen tap for a few minutes and contact your water company if it does not clear. If only your hot water is discoloured, the problem is more likely to be your cylinder or boiler.

Are iron and manganese harmful?

The UK limits in the Water Supply (Water Quality) Regulations 2016 are mainly set for appearance and taste. Iron at these levels is not considered a health risk. Manganese is a greater concern at higher concentrations, particularly for infants, so a supply that is well over the manganese limit should be treated and not used to make up baby formula.

The practical damage is real though: staining that is hard to clean, ruined laundry, blocked aerators and filter cartridges, and deposits that coat the quartz sleeve of a UV unit so bacteria are no longer reliably treated.

How to test for iron and manganese

Both are included in a standard private water supply test. It is worth testing pH at the same time, because acidic water can both dissolve iron from pipework and affect which treatment will work. See our results guide for how the figures compare with the limits.

How to remove iron and manganese from water

The right treatment depends on how much iron and manganese is present, the pH, and whether there is also hydrogen sulphide:

  • Oxidising filter media. A backwashing filter vessel containing media that converts dissolved iron and manganese into particles and traps them, then flushes them to drain automatically. This is the most common whole-house solution. See our iron and manganese reduction range.
  • pH correction first. Many oxidising media need water above a certain pH to work. If your water is acidic, a pH correction stage goes in front. See acidic water.
  • Water softeners. A softener can remove small amounts of dissolved iron as a side benefit, but it is not designed for it and higher levels foul the resin.
  • Sediment filtration. If the iron has already oxidised into particles, a sediment filter will catch them, but it will block quickly if levels are high.

On a private supply, iron and manganese treatment always goes before UV disinfection so the lamp sleeve stays clear.

Related contaminants

Why Wrekin Water

Wrekin Water is a family run company based in Bettisfield, Shropshire, serving more than 50,000 customers over 15 years and rated Excellent on Trustpilot. We size iron and manganese filters from your actual test results, and in North Shropshire we can install them for you. Send us your results for a recommendation.

Frequently asked questions

Groundwater holds dissolved iron while it is underground with little oxygen. When it meets air at the tap or in a cistern, the iron oxidises into tiny orange-brown particles, so clear water discolours after standing.

Black or dark brown specks and staining are usually caused by manganese, which occurs naturally in some groundwater. It can also build up as a black slime in pipes and cisterns.

Iron at the levels found in water is not considered a health risk; the 200 micrograms per litre UK limit is set for appearance and taste. Manganese is more of a concern at high levels, particularly for infants.

A softener can remove small amounts of dissolved iron, but it is not designed for it and higher levels foul the resin. A dedicated iron and manganese filter is the reliable solution.

Sudden brown water on a mains supply is usually sediment from old iron water mains disturbed by a burst or repair. Run the cold kitchen tap for a few minutes and contact your water company if it does not clear.