Is Borehole, Well or Spring Water Safe to Drink? A UK Owner's Guide to Testing
Updated: 1 day ago
Last reviewed: September 2026
Quick answer Is borehole water safe to drink? Borehole, well and spring water can be perfectly safe — but nobody checks it for you. Unlike mains water, it isn't treated or tested by a water company, and quality can change overnight after heavy rain. The biggest risk is bacteria (especially E. coli), followed by nitrate, iron and manganese, acidic water that dissolves metals from pipes, and — in some areas — natural arsenic. Test for bacteria at least once a year and after any big change, and do a full laboratory analysis when a supply is new or you buy the property.
On a private supply? Screen for bacteria at least once a year and after heavy rain, between your laboratory tests.
Who this applies to
About 1% of people in England and 3% in Wales get their water from a private supply rather than a water company. That includes:
Boreholes — narrow, drilled holes, often 40–75 m deep, lined with casing.
Wells — wider, usually shallower, often older and hand-dug.
Springs — water emerging naturally at the surface, usually collected in a tank.
Other sources — streams, lakes and even rainwater (see Is Rainwater Safe to Drink?).
Deeper, well-sealed sources are generally better protected from surface contamination than shallow wells and springs — but no source is risk-free.
Source | Typical depth | Main risks |
Borehole | Tens of metres | Natural chemistry (iron, manganese, arsenic in some areas), failed seals letting surface water in |
Well (dug) | Shallow | Surface water and bacteria after rain, run-off from fields |
Spring | At the surface | Bacteria after rain, nitrate from farmland, animals near the collection point |
Is borehole water safe to drink? The five risks that matter most
1. Bacteria (E. coli, coliforms, enterococci). The most common and most urgent problem. Faecal contamination from septic tanks, livestock or wildlife can reach a source, especially after heavy rain. Food Standards Scotland notes that "heavy rainfall can significantly deteriorate the microbiological quality of various water sources". See E. coli or Coliforms in Your Water Test?
2. Nitrate. From fertiliser, manure and septic systems. It matters most for bottle-fed babies: North Norfolk council's guidance says the legal limits "are based on World Health Organisation (WHO) recommendations to protect bottle fed infants under six months". The DWI confirms "the current drinking water standard is 50 mg/L".
3. Iron and manganese. Common in groundwater. They cause orange or black staining and a metallic taste, and can clog treatment systems. If you see staining, include them in a lab test.
4. Acidic (low-pH) water. Treatment works adjust pH partly "to reduce plumbosolvency" (water's tendency to dissolve lead), according to the Drinking Water Inspectorate. Private supplies carry an extra risk: the DWI notes that mains supplies are "often conditioned with phosphate to reduce the amount of lead dissolving", but this "is highly unlikely to be equipped in private water supply networks". Check pH and test for lead.
5. Natural chemicals from local rocks. Depending on geology, some areas have higher natural arsenic, fluoride or uranium. Parts of south-west England are known for arsenic-bearing rocks. Your source's geology decides whether this applies to you.
Private water supply regulations: what the council does
Local councils regulate private supplies, not water companies. What they do depends on who uses the water:
Commercial or public use (for example holiday lets, B&Bs, farms selling food, or supplies of 10 m³ a day or more): the council must risk-assess the supply and sample it at set frequencies — at least once a year.
Shared domestic supplies (several homes, under 10 m³ a day, no business use): a risk assessment and monitoring every five years.
A single private home: the council may monitor it, and must do so if the owner or occupier asks. Otherwise, testing is up to you.
Councils can charge for risk assessments and sampling, so ask about fees first.
What to test, and how often
When | What to test | How |
Every year (minimum) | Bacteria (E. coli, coliforms) | Home screen, lab or council sample |
After heavy rain, flooding or a long drought | Bacteria | Home screen within a few days; confirm any positive |
After work on the source, tank, pipes or treatment | Bacteria, plus whatever the work could affect | Home screen or lab |
When the water changes taste, smell or colour | Depends on the symptom | See our symptom guide |
New supply, buying the property, or every few years | Full chemistry (nitrate, metals, pH, arsenic, etc.) plus bacteria | Accredited laboratory |
Before choosing treatment | The specific problem you're treating | Lab, so the installer has real numbers |
Home screening or laboratory testing?
Both have a place:
Home screening is quick, cheap and good for regular checks and early warnings — for example, checking bacteria after heavy rain, or checking whether a problem has come back after treatment.
An accredited laboratory is the right choice for a first full analysis, for anything that affects guests, tenants or a sale, and to confirm any unexpected home result.
SustainWater's E. coli Test and Complete Drinking Water Test Kit are designed as screening tools between lab tests — not as a replacement for them.
Where to take the sample
On a private supply, where you sample changes what the result tells you:
Kitchen cold tap — what you actually drink. Start here.
After the treatment system — whether the UV or filters are working.
At the source or tank — whether the raw water has changed.
If the kitchen tap fails but the water after treatment passes, look at the pipes and tank between them. For step-by-step sampling, see How to Test Water Quality at Home.
Red flags: act now
Water becomes cloudy, coloured or smelly after rain.
Someone in the household has repeated stomach upsets.
The UV lamp or treatment alarm is off, or you've had a power cut.
A tank lid is missing, cracked or loose.
Flooding has reached the source, or animals have been near it.
A septic tank or soakaway nearby has failed.
In any of these cases, boil drinking water, test for bacteria, and contact your council if the result is positive.
Your local picture
Groundwater chemistry varies a lot from area to area. Use the SustainWater UK water testing map to see community test results and local context near you. It's community screening data, not official monitoring, but it shows what others nearby have found.
Test your water
Home screening between lab tests is the easiest way to spot a change early.
SustainWater home tests are screening tools. If a result is unexpected, or a health, legal or money decision depends on it, confirm it with an accredited laboratory.
Frequently asked questions
Is borehole water better than mains water? It can taste better and cost less to run, but it has no water company behind it. Its safety depends entirely on how well the source is protected, treated and tested.
Can I use a home test kit on borehole water? Yes, for regular screening — especially bacteria after rain. Use an accredited lab for the first full analysis and to confirm any unexpected result.
Does boiling make borehole water safe? Boiling kills bacteria but doesn't remove chemicals like nitrate, arsenic or lead. It's a short-term measure, not a fix.
How do I know if my spring water is safe after a drought? Low flows can concentrate natural chemicals, and the first heavy rain after a dry spell can wash contamination in. Test bacteria after the first big rainfall.
Do I have to tell the council I have a private supply? Councils keep registers of private supplies. If you let the property, run a business or share the supply, council regulation applies. If in doubt, ask your council's environmental health team.
Is well water safe to drink? It can be, but like borehole water it isn't treated or tested by a water company. Older, shallower wells are more exposed to surface water, so test for bacteria at least once a year and after heavy rain, and get a full laboratory analysis when you first use the supply.
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