Blue-green stains on your bath or basin, pinhole leaks in copper pipes, or a metallic taste are classic signs of acidic water. Acidic water is not usually harmful in itself, but it is corrosive: it slowly dissolves copper, lead and other metals from your plumbing and carries them to your tap. It is common on private supplies in upland and peaty areas, and it is straightforward to correct.
At a glance
- UK indicator range: pH 6.5 to 9.5
- Most at risk: springs, wells and boreholes in upland, moorland, peaty or some sandstone areas
- Signs: blue-green staining, pinhole leaks, metallic or bitter taste
- Fix: pH correction filters
What is pH?
pH measures how acidic or alkaline water is on a scale from 0 to 14. Pure water is neutral at 7. Below 7 is acidic and above 7 is alkaline. The scale is logarithmic, so water at pH 5.5 is ten times more acidic than water at pH 6.5. UK drinking water has an indicator range of 6.5 to 9.5 under the Water Supply (Water Quality) Regulations 2016.
Why is my water acidic?
Rain is naturally slightly acidic. When it soaks through peat, moorland soil or rock that contains little limestone, nothing neutralises it, so it reaches springs and boreholes still acidic. Water from these sources is often soft as well, which makes it even more corrosive. Mains water is treated to control corrosion before it is supplied, so acidic water is mostly a private supply issue.
Signs of acidic water
- Blue-green staining on baths, basins, showers and taps, where copper dissolved from the pipes is left behind as water evaporates.
- Pinhole leaks in copper pipework and early failure of hot water cylinders.
- Metallic or bitter taste, especially first thing in the morning.
- Blonde hair turning green after washing, from copper in the water.
Is acidic water harmful?
The acid itself is weak, but the metals it picks up are the concern. Acidic water can raise copper above its 2.0 mg/l limit and, in older properties, dissolve lead from pipes and solder. See lead in water and heavy metals. It also stops some iron and manganese treatments working, as many need water above a certain pH.
How to test pH
pH is part of every standard private water supply test. A laboratory test is best because it also measures the copper, lead and iron that acidic water carries, which tells you how urgent treatment is. Our results guide explains the figures.
How to fix acidic water
The usual solution is a neutralising filter: a vessel filled with a natural mineral such as calcium carbonate or magnesium oxide. As water flows through, it slowly dissolves a little of the mineral, which raises the pH. The media is used up gradually and topped up as part of routine servicing. See our pH correction range for systems, refillable cartridges and media.
pH correction normally sits at the start of a private supply treatment train, before iron and manganese filters and UV disinfection. Raising the pH also adds a little hardness, so check whether a softener is needed afterwards.
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 pH correction from your test results and supply the refill media to keep it working. In North Shropshire we can install it for you; elsewhere, ask our team.