Introduction
Safe drinking water is fundamental to public health, but its quality can be affected by chemical contaminants, pathogenic microorganisms, ageing distribution infrastructure, industrial activities and inadequate treatment or storage practices. Water that appears clear and has no unusual taste or odour may still contain contaminants that require laboratory analysis to detect.
In 2026, drinking-water quality continues to be an important concern for municipal water suppliers, industries, healthcare facilities, commercial establishments, residential communities, water-treatment operators and packaged drinking-water manufacturers.
Reliable water-quality assessment requires more than a basic pH or total dissolved solids (TDS) measurement. A comprehensive evaluation may include heavy metals, inorganic chemicals, microbiological indicators, physical characteristics and additional contaminants identified through a source-specific risk assessment.
In India, BIS IS 10500:2012, Drinking Water — Specification, together with its applicable amendments, remains a key reference for drinking-water quality. Internationally, the World Health Organization’s Guidelines for Drinking-water Quality, updated in June 2026, provide guidance on health-based targets, water-safety planning, microbial hazards and chemical risks.
This article explains the key drinking-water contaminants, advanced analytical techniques, sampling considerations and practical steps organisations can take to strengthen water-quality monitoring.
Understanding Drinking Water Quality
Drinking-water quality is assessed through a combination of physical, chemical and microbiological characteristics. The parameters selected for testing depend on the water source, treatment process, distribution system, intended use and applicable regulatory requirements.
- Physical parameters help assess characteristics such as colour, turbidity, odour and total dissolved solids.
- Chemical parameters include pH, hardness, alkalinity, major ions, selected inorganic contaminants, heavy metals and, where relevant, organic chemicals.
- Microbiological parameters help identify faecal contamination and other indicators of inadequate treatment or distribution-system integrity.
No single parameter can establish that water is safe. For example, acceptable TDS does not demonstrate the absence of lead, arsenic or disease-causing microorganisms. Similarly, a microbiologically satisfactory result does not establish that the water meets chemical-quality requirements.
A suitable testing programme should therefore be designed around the relevant risks rather than relying on one general water-quality indicator.
Heavy Metals in Drinking Water: Sources and Health Concerns
Heavy metals and other toxic elements may enter drinking water through natural geological formations, industrial discharges, mining activities, contaminated groundwater, treatment chemicals, plumbing materials and corrosion of distribution infrastructure.
Their presence may be difficult to detect without analytical testing because many metals do not produce obvious changes in water appearance, taste or smell at concentrations of concern.- Lead
Lead contamination may arise from certain plumbing materials, solder, fittings and corrosion of older distribution systems.
Exposure to lead can affect multiple body systems. Children are particularly vulnerable to its effects on neurological development, while exposure during pregnancy is also a concern. Lead testing may be especially relevant where water comes into contact with older plumbing, building infrastructure or materials that may release the metal.- Arsenic
Arsenic can occur naturally in groundwater and may also be associated with industrial or mining activities.
Long-term exposure to inorganic arsenic through drinking water is associated with serious health effects, including an increased risk of certain cancers. Groundwater sources in areas with known geological arsenic occurrence may require targeted monitoring and, where necessary, treatment verification.- Cadmium
Cadmium can enter water through industrial contamination, waste disposal and other environmental sources. Chronic exposure can affect the kidneys and may contribute to other adverse health outcomes.
Testing may be particularly relevant when a water source is influenced by industrial activities or when a source-specific assessment identifies a potential risk.- Mercury
Mercury contamination may be associated with certain industrial processes, waste streams and environmental sources. Its occurrence and chemical form influence the appropriate analytical approach and risk interpretation.
Laboratories should use methods suitable for the relevant mercury species or total mercury determination, depending on the testing objective.- Chromium
Chromium may occur in water from natural sources or industrial activities, including metal finishing and certain manufacturing processes.
The distinction between total chromium and hexavalent chromium is important because different chemical forms have different toxicological characteristics. Where the risk assessment requires it, speciation-specific testing may be necessary rather than relying solely on total chromium.
Other important chemical parameters
A drinking-water assessment may also include fluoride, nitrate, nitrite, iron, manganese, aluminium, chloride, sulphate, hardness and other parameters according to the applicable standard and source characteristics.
Fluoride and nitrate deserve particular attention because naturally elevated concentrations or contamination from agricultural and other activities can affect groundwater quality. The analytical plan should distinguish health-related contaminants from parameters that primarily indicate acceptability, operational performance or treatment effectiveness.Microbiological Safety: Detecting Potentially Harmful Contamination
Microbiological contamination is a major drinking-water safety concern because pathogens can cause illness even when water looks clean.
Contamination may occur at the source, during treatment, through damaged distribution pipes, following intermittent water supply, or during storage in tanks and containers.- Escherichia coli (E. coli)
E. coli is an important indicator of faecal contamination. Its detection in drinking water can indicate that contamination has occurred and that enteric pathogens may also be present.
A positive result should trigger a prompt investigation and appropriate risk-management action under the relevant water-safety procedures.- Total coliform bacteria
Total coliform testing can help assess treatment and distribution-system integrity, although these organisms are not all specific indicators of faecal contamination.
Their detection should be interpreted alongside E. coli results, sampling conditions, treatment history and the applicable standard.- Other microbial hazards
Depending on the water source and risk assessment, drinking water may also require consideration of viruses, protozoa and other pathogens.
Organisms such as Giardia and Cryptosporidium can present particular challenges because their resistance to some disinfection processes differs from that of many bacteria. Routine indicator-organism testing does not necessarily detect every pathogen. Where a specific hazard is suspected, targeted investigation may be required.- Common microbiological testing approaches
Membrane filtration: A measured volume of water is passed through a membrane that retains microorganisms. The membrane is then cultured using an appropriate procedure for detection or enumeration.
Most probable number (MPN): A statistical approach used to estimate microbial concentration from growth patterns across replicate samples.
Presence/absence testing: Used to determine whether a specified microorganism or indicator is detected in the tested sample volume.
Molecular methods: Techniques such as PCR may help detect selected microbial targets in appropriate applications. However, molecular detection does not always establish organism viability and should not automatically be treated as a substitute for a prescribed regulatory method.
The correct method depends on the target organism, water matrix, required detection capability and applicable regulatory requirements.
Regulatory Landscape in 2026
Drinking-water requirements differ according to whether the water is supplied through a public distribution system, used in an industrial facility, assessed for a commercial building or sold as packaged drinking water.
Indian drinking-water specification: BIS IS 10500
BIS IS 10500:2012, including applicable amendments, is an important Indian reference for assessing drinking-water quality.
The specification addresses a range of physical, chemical and microbiological characteristics and includes acceptable limits and, for specified parameters, permissible limits under defined conditions. The appropriate interpretation depends on the parameter, the applicable provision and the circumstances under which a permissible limit may be used. A permissible limit should not be treated as a general substitute for the acceptable limit. For compliance assessment, laboratories and water suppliers should refer to the current applicable edition and amendments rather than relying on an old parameter table or an unverified online summary.
WHO Guidelines for Drinking-water Quality: 2026 update
In June 2026, the World Health Organization released the fourth edition of its Guidelines for Drinking-water Quality, incorporating the first, second and third addenda.
The updated guidance reinforces a preventive approach based on:
- Health-based targets.
- Water-safety plans.
- Sanitary inspections.
- Microbial hazard management.
- Independent surveillance and verification.
- Risk-based improvement of water supplies.
The guidelines support the development of national policies and standards. They are not a direct replacement for India’s applicable regulatory requirements.
Packaged drinking water in India: testing requirements
Packaged drinking water and mineral water require separate regulatory consideration from general drinking-water supply.
FSSAI issued a scheme of testing for packaged drinking water and mineral water in December 2025, directing food business operators to comply from 1 January 2026. This followed the removal of the previously mandatory BIS certification requirement for these products under the relevant FSSAI regulatory framework.Manufacturers should therefore verify the applicable FSSAI licensing, testing, sampling, frequency and reporting requirements for their product category. They should not assume that the absence of a mandatory BIS certification mark removes the obligation to demonstrate product safety and compliance.
The applicable requirements should be confirmed from the current FSSAI scheme and any subsequent official amendments or directions.Advanced Analytical Testing for Drinking Water
Advanced analytical methods can provide the sensitivity, selectivity and measurement capability required to assess contaminants at low concentrations. Method selection should be based on the target analytes, sample matrix, required reporting limit and applicable standard.
- ICP-MS: Inductively Coupled Plasma Mass Spectrometry
ICP-MS is a highly sensitive technique used to determine many elements at trace and ultra-trace concentrations.
Depending on the validated method and instrument configuration, it can support multi-element analysis for contaminants such as lead, arsenic, cadmium, chromium and other relevant elements.Key applications include:
- Trace-element screening and quantification.
- Multi-element testing of drinking-water samples.
- Investigation of suspected metal contamination.
- Verification of water-treatment performance
Interferences, sample preparation, calibration, contamination control and quality-control checks must be addressed to ensure reliable results.
- ICP-OES: Inductively Coupled Plasma Optical Emission Spectrometry
ICP-OES measures the characteristic optical emissions of elements excited in an inductively coupled plasma.
It can be suitable for multi-element analysis across a range of concentration levels and may be selected for routine testing where the required sensitivity is achievable.
The choice between ICP-MS and ICP-OES depends on the elements of interest, expected concentrations, required detection limits, matrix and applicable method.
- Atomic Absorption Spectrometry (AAS)
AAS is another established technique for determining selected metals in water.
Depending on the element and analytical configuration, flame AAS or graphite furnace AAS may be used. Specialised approaches may be appropriate for certain elements, including mercury. AAS can be suitable for targeted analysis, while multi-element techniques may offer operational advantages when several elements need to be measured in the same sample.- Ion chromatography (IC)
Ion chromatography is used to separate and quantify selected anions and cations.
Depending on the method, it can support analysis of parameters such as chloride, fluoride, nitrate, nitrite and sulphate. It may also be used for other ionic species where the method is suitable. Ion chromatography is valuable when conventional screening indicates a potential issue involving inorganic ions or when a more detailed chemical profile is required.- Advanced microbiological methods
Conventional culture-based methods remain important for many routine drinking-water compliance applications.
Molecular techniques, including PCR-based methods, can provide additional information for selected microbial targets. However, their suitability depends on the test objective, target organism, method validation and regulatory acceptance. Where results are used for regulatory decisions, the laboratory should confirm that the method meets the applicable requirements.- Additional analytical techniques
Depending on the identified risks, water analysis may also require techniques such as:
- UV-visible spectrophotometry for selected chemical parameters.
- Gravimetric or instrumental methods for total dissolved solids and other physical-chemical characteristics.
- Gas chromatography or liquid chromatography for selected organic contaminants.
- Specialised radiological methods where radionuclide contamination is a relevant concern.
Why Sampling and Sample Preservation Matter
Even a technically sound analytical method can produce misleading results if the sample is not representative or has not been handled appropriately.
Water quality may vary by source, time, treatment stage, storage conditions and point of collection. Sampling procedures should therefore be planned before laboratory testing begins.
Important considerations include:
- Sampling location: Samples may be required from the source, treatment plant outlet, storage tank, distribution network or point of use.
- Container selection: The container must be appropriate for the target parameters. Trace-metal testing, organic contaminant analysis and microbiological testing may require different containers.
- Preservation: Certain chemical samples require specific preservatives or temperature conditions. Microbiological samples need appropriate sterile containers and timely handling.
- Disinfectant neutralisation: Where chlorinated water is sampled for microbiological testing, an appropriate neutraliser may be required to prevent residual disinfectant from continuing to affect microorganisms after collection.
- Transport and holding time: Samples should be transported and analysed within the applicable holding time under suitable conditions.
- Sampling documentation: Record the collection point, date, time, sampling method, water source, treatment status and any relevant observations.
For lead or other contaminants that may be influenced by plumbing, the sampling protocol should be selected according to the investigation objective. A first-draw sample and a flushed sample, for example, may provide different information and should not be considered interchangeable.
Drinking Water Testing for Different Industrie
Testing requirements should reflect the intended use of water and the risks associated with each facility.
| Sector | Key testing considerations |
|---|---|
| Municipal and community water supplies | Source quality, treatment performance, distribution integrity and microbiological safety |
| Hospitals and healthcare facilities | Chemical and microbiological quality, storage and point-of-use risks |
| Pharmaceutical and healthcare manufacturing | Water quality appropriate to the specific process and applicable pharmacopoeial or regulatory requirements |
| Food and beverage manufacturing | Water used as an ingredient, in processing, cleaning and other relevant operations |
| Hotels, offices and residential complexes | Incoming supply, overhead and underground tanks, plumbing and point-of-use quality |
| Packaged drinking-water manufacturers | Product-category requirements, treatment controls, finished-product testing and documented compliance |
| Industrial facilities | Source-specific chemical risks, process requirements and intended water use |
A general drinking-water test should not automatically be considered sufficient for pharmaceutical process water, specialised manufacturing applications or other uses subject to additional standards.
Developing a Risk-Based Water Quality Monitoring Programme
A structured monitoring programme helps organisations detect changes, investigate contamination and verify treatment performance.
- Identify the water source. Determine whether the supply comes from groundwater, surface water, municipal distribution, tanker supply or a packaged product.
- Assess potential hazards. Review local geology, nearby industrial activities, agricultural influences, plumbing materials, storage tanks and treatment processes.
- Select relevant parameters. Choose physical, chemical and microbiological tests based on the applicable standard and source-specific risks.
- Establish sampling points and frequency. Determine where and how often samples should be collected. Frequency should reflect regulatory requirements, source variability, previous results and operational risk.
- Select suitable analytical methods. Confirm that the method can achieve the required reporting limit and is appropriate for the intended compliance assessment.
- Review trends, not only individual results. Repeated measurements can help identify gradual changes, seasonal variation, treatment failure or emerging contamination.
- Define corrective actions. Establish procedures for investigating unsatisfactory results, notifying responsible personnel, implementing immediate controls and verifying the effectiveness of corrective measures.
What Should Be Included in a Water Testing Report?
A useful water testing report should provide sufficient information to understand the sample and interpret the results.
Depending on the test and reporting requirements, it may include:
- Sample identification and description.
- Sampling location and collection details, where supplied or recorded.
- Parameters tested and analytical methods used.
- Results and units of measurement.
- Applicable specification or reference limits, where requested and appropriate.
- Relevant detection or quantification limits.
- Deviations, qualifications or limitations affecting interpretation.
- Appropriate reporting and authorisation details.
The laboratory report should be evaluated against the correct standard and intended use. A result should not be labelled compliant or non-compliant using an unrelated limit or an outdated specification.
How Eureka Supports Drinking Water Quality Assessment
Eureka provides analytical testing support for businesses and organisations seeking to evaluate water quality and strengthen quality assurance programmes.
Depending on the applicable testing scope and method availability, support may include:
- Chemical testing: Assessment of selected physical and chemical water-quality parameters.
- Heavy metal analysis: Testing for relevant elements according to the sample type and required analytical method.
- Microbiological testing: Assessment of specified microbiological indicators using suitable methods.
- Risk-based testing plans: Support in identifying appropriate testing parameters based on water source, intended use and customer requirements.
- Analytical reporting: Results to support internal quality monitoring, investigation and applicable compliance assessments.
The appropriate testing plan depends on the water source, intended use, required parameters and applicable regulatory framework. Customers should confirm method availability, sample-container requirements, preservation conditions and the intended use of results before sample submission.
Conclusion
Drinking-water safety requires a coordinated approach that addresses chemical contamination, microbiological hazards, treatment performance and the integrity of the distribution system.
Heavy metals such as lead, arsenic, cadmium, mercury and chromium may require sensitive instrumental analysis, while microbiological testing helps identify evidence of contamination and failures in treatment or distribution. Advanced techniques such as ICP-MS, ICP-OES, AAS and ion chromatography can support targeted assessment when selected according to the required analytical performance.
In 2026, organisations in India should pay particular attention to the applicable BIS drinking-water specification, the updated WHO guidance and the distinct FSSAI testing requirements for packaged drinking water and mineral water.
A reliable monitoring programme combines representative sampling, appropriate analytical methods, documented interpretation and prompt corrective action. Regular, risk-based testing helps organisations make better-informed decisions about water quality and protect the people who depend on their supply.
Frequently Asked Questions (FAQ)
1. What are the most important parameters for drinking-water testing?
The appropriate parameters depend on the water source and intended use. Common assessments include pH, turbidity, TDS, hardness, selected inorganic chemicals, heavy metals and microbiological indicators such as E. coli and total coliforms.
2. Why should drinking water be tested for heavy metals?
Certain metals can pose health risks at low concentrations and may not produce visible changes in water. Testing can help identify contamination from natural sources, industrial activities, plumbing and other potential sources.
3. Which instrument is suitable for heavy metal analysis in water?
ICP-MS, ICP-OES and AAS are established analytical approaches. The appropriate technique depends on the target elements, expected concentrations, required detection limits and applicable method.
4. Does a low TDS result mean water is safe to drink?
No. TDS is a general measure of dissolved substances. It does not establish that water is free from pathogens or toxic contaminants such as lead and arsenic.
5. What is the difference between E. coli and total coliform testing?
E. coli is an important indicator of faecal contamination. Total coliforms are a broader group of organisms that can help assess water-system integrity but are not all specific indicators of faecal contamination.
6. How frequently should drinking water be tested?
The appropriate frequency depends on the applicable regulations, water source, intended use, system size, previous results and risk assessment. A single test should not automatically be treated as evidence of continuing water safety.
7. What is the difference between general drinking water and packaged drinking water testing in India?
General drinking-water assessment commonly refers to the applicable drinking-water specification, including BIS IS 10500. Packaged drinking water and mineral water are also subject to their applicable FSSAI requirements, including the scheme of testing effective from 1 January 2026.
8. Can one sample represent an entire building's water supply?
Not always. Water quality may differ between the incoming supply, storage tanks, different floors, plumbing systems and individual taps. Sampling points should reflect the purpose of the investigation.
9. Why is sample preservation important?
Incorrect containers, inadequate preservation, delayed transport or excessive holding times can affect analytical results. Different parameters require different sampling and handling procedures.
10. What should an organisation do if a drinking-water sample fails a relevant criterion?
The organisation should assess the potential risk, inform responsible personnel, implement appropriate interim controls, investigate the source, arrange confirmatory testing where justified and verify corrective actions in accordance with applicable requirements.
Official References
- Bureau of Indian Standards — IS 10500:2012, Drinking Water — Specification, including applicable amendments
- World Health Organization — Guidelines for Drinking-water Quality: Fourth Edition Incorporating the First, Second and Third Addenda (2026)
- World Health Organization — Water Safety Plan Guidance and Sanitary Inspection Resources
- Food Safety and Standards Authority of India — Scheme of Testing for Packaged Drinking Water and Mineral Water (2025; effective 1 January 2026)
- Food Safety and Standards Authority of India — Applicable Food Safety and Standards Regulations for Packaged Drinking Water and Mineral Water
- Bureau of Indian Standards — IS 3025 series, Methods of Sampling and Test for Water and Wastewater
- Bureau of Indian Standards — IS 15185, Water Quality: Detection and Enumeration of Escherichia coli and Coliform Bacteria by Membrane Filtration Method
- United States Environmental Protection Agency — Drinking Water Analytical Methods and Contaminant Information
