Copper in Tap Water UK: Causes, Limits & Green Staining

What Causes Copper in Tap Water?

Copper in UK tap water comes almost entirely from your home's plumbing. Copper pipes have been the standard for domestic plumbing since the 1950s, and small amounts of copper dissolve into the water as it passes through them.

The amount of copper that dissolves depends on:

  • Age of pipes: New copper pipes leach more copper. A protective patina forms over months to years, reducing dissolution.
  • Water pH: Acidic water (low pH) dissolves more copper. Soft water areas (Scotland, Wales, South West) tend to have lower pH.
  • Standing time: Water that sits in copper pipes overnight contains more copper than running water.

UK Legal Limits

The DWI sets the limit at 2 mg/l (2000 ppb). Typical UK tap water contains 10-100 ppb, well below the limit. New-build homes may temporarily exceed this in the first few weeks.

Green Staining

If you notice blue-green stains on your sanitaryware, this indicates elevated copper levels. While usually still within safe limits, it's worth running the tap for 30 seconds before drinking and checking with your water company if the staining is persistent.

Health Effects

Copper is an essential nutrient — adults need about 1.2 mg per day. At normal tap water levels, copper contributes a small amount to your dietary intake. Problems only occur at much higher levels:

  • Above 2 mg/l: Can cause nausea, stomach cramps, and diarrhoea
  • Long-term high exposure: Potential liver damage (extremely rare from tap water)
  • Wilson's disease patients: Cannot process copper normally and should monitor intake carefully

Check Your Water's Copper Level

Enter your postcode on WaterGrade to see the copper measurement for your supply zone.

Frequently Asked Questions

Why is there copper in my tap water?

Copper in tap water comes from copper pipes and fittings in your home's plumbing. Small amounts dissolve into the water, especially when water sits in the pipes for long periods or when the plumbing is new. Soft, acidic water dissolves more copper than hard water.

What is the legal limit for copper in UK drinking water?

The UK legal limit for copper in drinking water is 2 mg/l (2000 ppb). Most UK tap water contains less than 100 ppb. Higher levels are most common in homes with new copper plumbing or in areas with soft, slightly acidic water.

What causes green staining from tap water?

Green or blue-green stains on sinks, baths, and toilets are caused by dissolved copper in the water. This is most common in homes with new copper pipes or in areas with soft, acidic water (pH below 7). The staining is cosmetic and the copper levels are usually safe, but it indicates elevated copper content.

Is copper in drinking water harmful?

At normal UK levels (below 100 ppb), copper in drinking water is not harmful — copper is actually an essential trace mineral. At higher levels (above 2 mg/l), it can cause nausea, vomiting, and stomach cramps. Long-term exposure to very high levels can cause liver damage, but this is extremely rare with UK water supplies.

Check Your Water Quality

Enter your UK postcode for an instant water quality report graded A-F.

Check My Postcode

Check Water Quality in Other Cities

London Manchester Birmingham Leeds Glasgow Edinburgh Liverpool Sheffield Newcastle upon Tyne Cardiff Belfast Nottingham Southampton Brighton Oxford