Start with evidence, not a shopping basket
If your home is on a public mains supply, your water company already samples and tests the water against drinking-water requirements. The Drinking Water Inspectorate (DWI) explicitly recommends obtaining your local water-quality report before buying a filter or softener. That report is the sensible starting point because it tells you what was actually measured in your supply area and the standards against which those results are assessed.
That does not mean every household will love the water exactly as supplied. Hardness can leave scale, chlorine can be noticeable to sensitive noses, old plumbing can introduce metals after water has left the network, and some people simply prefer a different taste. The point is to separate preference, plumbing, hardness and health-related water quality rather than treating them as one problem.
Step 1: identify your supplier
Your bill is the easiest route. If you do not have one to hand, Water UK's supplier finder accepts a postcode and identifies the water and wastewater companies serving the address. Once you know the drinking-water supplier, use that company's own postcode/supply-zone quality tool or request its report.
Useful distinction: the company that supplies drinking water is not always the same organisation that handles wastewater. For water-quality questions, you want the drinking-water supplier.
Step 2: read the report without panicking at every detection
Reports commonly show a parameter, unit, regulatory standard or prescribed concentration/value, number of samples and a range or result. A substance appearing in a table does not mean the water has “failed”. Compare the result with the stated standard, note the units, and read the supplier's explanatory notes.
Pay particular attention to whether the figure is a maximum, minimum, mean or single result. A value in micrograms per litre (µg/L) is one-thousandth of the same numerical value in milligrams per litre (mg/L); mixing those units can turn an ordinary result into a frightening-looking number.
Step 3: treat hardness as a separate question
Hardness mainly reflects dissolved calcium and magnesium. It affects scale, soap lather and appliance maintenance, but DWI notes that UK drinking-water regulations do not set a health standard for hardness. A hard-water result is therefore not evidence that your tap water is unsafe.
Use our hardness converter if your supplier reports °dH, °fH, ppm or mg/L as CaCO₃, then read what hard water actually means.
Step 4: investigate property plumbing where appropriate
A supply-zone report cannot tell you everything that happens between the street and your glass. DWI says lead was commonly used in service pipework before 1970, and older properties that have not been modernised may still contain lead pipes. If you suspect lead, ask your water company about testing and investigate the plumbing rather than assuming a generic countertop filter is the complete solution.
Step 5: match the treatment to the problem
| What bothers you? | What to investigate first | RO? |
|---|---|---|
| Slight chlorine taste | Chill tap water; consider activated carbon if taste remains an issue. | Usually more treatment than necessary for taste alone. |
| Scale in kettle/shower | Hardness and whole-house scale strategy. | RO reduces hardness in its treated stream, but is not a whole-house softener. |
| Specific contaminant | Confirm it is present; choose independently verified treatment for that substance. | Potentially, depending on the contaminant and certified claims. |
| Broad dissolved-solids reduction | Compare RO systems, efficiency, maintenance and remineralisation. | Yes, this is a core strength of RO. |
| Private well/borehole/spring | Risk assessment and laboratory testing. | May be one stage in a multi-barrier system, not a substitute for diagnosis/disinfection. |
What a home TDS meter can—and cannot—add
A TDS/conductivity meter is useful for comparing feed and RO product water and spotting trends. It cannot tell you whether lead, nitrate, PFAS, bacteria or a particular pesticide is present. A low number is not a laboratory certificate. See TDS explained.
When to contact the supplier rather than filter the symptom
If water suddenly develops a strong or persistent unusual taste, smell or appearance, contact the water company. DWI advises contacting the supplier if a bad or strong taste or odour makes the water unpalatable. A filter should not be used to mask a new supply or plumbing problem that ought to be investigated.
Private supplies are different
A borehole, spring, well or other non-water-company source is not simply “tap water without chlorine”. Catchment risks, storage, treatment and microbiological hazards all matter. Local authorities regulate private supplies in England and Wales and use risk assessment and monitoring. Start with our private water supply guide.
Sources and further reading
For factual claims that matter to health, regulation or product performance, we prefer primary and official sources. Useful references for this guide include:
- Drinking Water Inspectorate — Domestic water filters and softeners
- Drinking Water Inspectorate — Lead in drinking water
- Drinking Water Inspectorate — Chlorine
- Water UK — Find your supplier
- Drinking Water Inspectorate — Guide for private supply owners/users
Related guides
Last reviewed: 6 October 2026. This guide is written for a UK audience. Always follow current supplier, regulator, manufacturer and healthcare advice where it applies.