Start with the lab report and the intended use. A filter’s certification must cover the specific contaminant you want to reduce.
1. Turn the report into a treatment brief
Separate three questions: is there a health-related contaminant, is there an aesthetic problem, and is water damaging equipment? A taste complaint and a microbiological result need different responses. A TDS meter cannot tell you whether bacteria, nitrate or a specific toxic chemical is absent.
Write down each measured substance, its unit, the relevant local limit and the required treated-water target. Preserve the original report; transcription errors such as mixing mg/L and µg/L change the meaning by a factor of one thousand.
2. Choose whole-house or drinking-water treatment
Point-of-use treatment serves a tap or drinking-water outlet. Point-of-entry equipment serves water entering the home. Choose the scope according to the contaminant and how people are exposed. Confirm the product’s documented contaminant-reduction claim, capacity and flow rate.
Sediment filtration, carbon, softening, reverse osmosis and disinfection do different jobs. They are not automatically interchangeable, and every system needs maintenance. Match the technology to measured water quality instead of buying the greatest number of stages.
CDC · Choosing home water filters ↗3. Check how the stages work together
Ask the supplier for a treatment flow diagram. For each stage, request inlet-water limits, service flow, pressure drop, consumables and any backwash or reject-water flow. Pretreatment should protect later equipment while meeting the actual contaminant targets.
UV performance depends on the specified water clarity and operating conditions; it does not remove dissolved chemicals. Softening addresses hardness but is not general disinfection. RO performance depends on the particular system and its reduction claims. Treat the comparison below as a discussion aid, not a diagnosis from symptoms.
4. Verify and maintain the result
Sample treated water after installation using the laboratory’s procedure. Keep raw and treated results together so you can see whether the target was met. Record cartridge dates, pressure readings, backwash settings and service intervals in the equipment record.
Check replacement cost before buying. A system that depends on unavailable cartridges or power during an outage may not suit an autonomous home. Follow local advice if test results show a health risk; commissioning a filter does not by itself prove that the water is safe.
Treatment technologies: purpose and limits
| Technology | Potential role | What it does not establish |
|---|---|---|
| Sediment filter | Reduce suspended particles | Microbiological or dissolved-chemical safety |
| Activated carbon | Specified taste or chemical reduction | Universal removal of salts or germs |
| Ion-exchange softener | Reduce hardness | General drinking-water disinfection |
| Reverse osmosis | Reduce specified dissolved contaminants | Performance for an unlisted contaminant |
| UV system | Inactivate microbes under rated conditions | Removal of dissolved chemicals |
Worked example
Check service flow, not just daily litres
Suppose two showers use 8 L/min each and a kitchen tap uses 5 L/min at the same time.
Simultaneous demand = 8 + 8 + 5 = 21 L/min = 1.26 m³/h
Ask for treatment performance and pressure loss at that flow. A unit’s daily capacity alone does not show whether it will serve the peak. These fixture rates are illustrative.
What to have ready
- Raw-water report with units
- Specific treatment target for each contaminant
- Certified reduction claims at required flow
- Consumables, drainage and power requirements
Common mistakes
- Selecting a treatment train from water colour alone.
- Equating lower TDS with safe drinking water.
- Ignoring pressure loss or backwash flow.
Reference check: 5 September 2026. Sources include US public agencies. Principles are general; regulations and design values must be checked where you live.Worked examples use stated hypothetical inputs.