Purifying well or borehole water is not about buying one filter. It is about finding out what is in your water, fixing the source where you can, and then installing the right treatment in the right order. This guide walks through each step for UK private water supplies, from the first test to the maintenance that keeps your water safe year after year.
Step 1: Test your water first
Every good treatment system is designed from a test result. Well water can look, smell and taste perfect and still contain E. coli, nitrate or arsenic, while a supply with harmless orange staining may only need an iron filter. Without a test you risk paying for equipment you do not need, or missing the thing that matters.
A laboratory private water supply test should cover bacteria, metals (iron, manganese, lead, copper and arsenic where the geology suggests it), nutrients (nitrate, nitrite, ammonium) and physical parameters (pH, conductivity, turbidity, colour). Home test strips are useful for quick checks such as hardness, but not for safety decisions. Our water test results guide explains every figure on the report.
Step 2: Protect the source
Treatment works best when it is not fighting a problem that could be stopped at the source. Before or alongside fitting equipment, check:
- The well or borehole head. It should have a sealed, raised cap so surface water, insects and small animals cannot get in. Cracked covers and open chambers are a common cause of bacterial contamination.
- Distance from septic tanks and soakaways. Waste water systems close to or uphill of the source can contaminate it with bacteria and nitrate.
- Livestock and slurry. Fence animals away from springs and wellheads, and be aware of muck-spreading on surrounding land.
- Storage tanks. Tanks need close-fitting lids and regular cleaning, especially any tank after the UV unit.
After work on the source, flooding or a bacterial failure, the borehole and pipework may need to be disinfected by a specialist before you rely on your treatment system.
Step 3: Match treatment to the result
| Test finds | What it means | Treatment |
|---|---|---|
| E. coli or coliforms | Contamination from faeces, soil or surface water | Sediment filtration then UV disinfection |
| pH below 6.5 | Acidic water that dissolves copper and lead from plumbing | pH correction |
| Iron or manganese over the limit | Orange, brown or black staining; fouls UV sleeves | Iron and manganese filtration |
| Rotten egg smell | Hydrogen sulphide gas | H2S treatment or catalytic carbon |
| Nitrate over 50 mg/l | Fertiliser, slurry or septic tank influence | Nitrate reduction or reverse osmosis |
| Arsenic or other heavy metals | Natural geology or old plumbing | Arsenic reduction or reverse osmosis |
| High turbidity or sediment | Silt and clay, often worse after rain | Sediment and pleated filters |
| High hardness | Limescale in kettles, boilers and on the UV sleeve | Water softener; see how hard is my water? |
For a fuller explanation of each contaminant, see our guide to water contaminants.
Step 4: Install treatment in the right order
When a supply needs several stages, the order matters. Each stage protects the next, and UV disinfection always goes last so it receives clear, clean water. A typical well water treatment train runs:
-
1
Coarse pre-filter
Catches sand and grit to protect pumps, valves and the stages that follow.
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2
pH correction
Raises the pH of acidic water so it stops corroding pipes and so iron filters can work.
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3
Iron, manganese and H2S removal
Oxidising filter media turn dissolved metals and gases into particles and backwash them away.
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4
Softening or nitrate removal
Ion exchange for hardness or nitrate, where the test calls for it.
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5
Fine sediment filter
A 5 micron (or finer) cartridge removes the last particles that could shade bacteria from UV light.
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6
UV disinfection
Inactivates bacteria, viruses and parasites without chemicals, as the final barrier.
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7
Drinking water polish (optional)
Reverse osmosis at the kitchen tap for nitrate, arsenic, lead or taste.
Not every supply needs every stage. A clean, neutral borehole may only need sediment filtration and UV; an acidic upland spring needs pH correction first; an iron-rich borehole needs an iron filter before the UV unit.
The main treatment technologies explained
Sediment filtration
Cartridge or backwashing filters that physically strain out sand, silt and rust. They do not remove bacteria or dissolved chemicals, but nothing downstream works well without them. See sediment filters and whole house filtration.
UV disinfection
Water flows past an ultraviolet lamp inside a stainless steel chamber. The UV light damages the DNA of micro-organisms so they cannot reproduce. It adds nothing to the water and does not change taste, but it only works on clear water and leaves no residual, so it must be sized for your peak flow and maintained. Browse UV systems and read our UV FAQs.
pH correction
A vessel or cartridge of natural calcium carbonate or magnesium oxide that slowly dissolves into acidic water to raise its pH. The media is topped up as it is used. See pH correction.
Iron and manganese filters
Backwashing filters containing oxidising media that convert dissolved iron and manganese into particles, trap them, then flush them to drain automatically. See iron and manganese reduction.
Activated carbon
Adsorbs organic compounds, some pesticides, and taste and odour; catalytic carbon also handles low levels of hydrogen sulphide. It does not remove bacteria, nitrate or most metals. See carbon filters.
Water softeners and nitrate units
Ion exchange resins that swap hardness minerals or nitrate for sodium or chloride, regenerated with salt. See water softeners and nitrate reduction.
Reverse osmosis
A membrane that removes most dissolved substances, including nitrate, arsenic, lead and fluoride, usually fitted under the kitchen sink for drinking and cooking water. It produces a waste stream and needs pre-filtration, so it complements whole-house treatment rather than replacing it. Do not rely on RO alone for bacteria on a private supply; keep UV in place. See reverse osmosis systems.
Step 5: Maintain your system
| Task | How often |
|---|---|
| Replace the UV lamp | Every 12 months, even if it still lights; UV output falls with use |
| Clean or replace the quartz sleeve | At every lamp change, or sooner if water is hard or iron-rich |
| Change sediment cartridges | Every 3 to 6 months, or when pressure drops |
| Top up pH correction media | As the level drops, typically checked every 6 to 12 months |
| Check backwashing filters and softener salt | Monthly visual check |
| Bacteria test | At least once a year, and after any change or flooding |
| Full chemical test | Every few years, or if taste, smell or colour changes |
Private water supply regulations
In England, private supplies are covered by the Private Water Supplies (England) Regulations 2016, as amended, and must meet the same standards as mains water. A supply serving only your own home is your responsibility; your council does not have to test it unless you ask. Shared supplies, and any supply used for a holiday let, tenancy or business, are risk assessed and sampled by the local authority. The Drinking Water Inspectorate publishes guidance, and our regulations guide and landlord and business testing page explain what applies to you. Buying or selling? See water testing for property sales.
Get a system designed from your results
Wrekin Water is a family run company based in Bettisfield, Shropshire. We have served more than 50,000 customers over 15 years, are rated Excellent on Trustpilot, and private water supplies are one of our specialist areas. Send us your test results and we will design a treatment train for your supply. In North Shropshire we can install it for you. Contact our team or start with drinking water testing.