Inside the ETR Laboratory: How Samples Are Analyzed
Most people who order a water test never see what
Free Shipping on Orders of $100 or More
Free Shipping on Orders of $100 or More
A water test can tell you much more than whether your water simply “passes” or “fails.” Depending on what is included in the analysis, a laboratory can measure bacteria, metals, minerals, chemicals, radioactive contaminants, and general characteristics such as pH and hardness. Together, these water quality parameters can reveal potential health concerns, explain staining or scale buildup, and point to problems with a well, plumbing system, or surrounding environment.
There is no universal set of exactly 12 parameters that every laboratory tests. The right analysis depends on the water source, location, property, suspected contamination, and reason for testing. However, the following 12 represent some of the most useful physical, chemical, and biological water parameters for understanding residential drinking water. Many are also relevant to commercial and industrial water testing, where water quality can affect equipment, processes, and finished products.
If you have ever wondered what a water test measures, these are some of the results you are most likely to encounter and what each one can tell you.
Total coliform and E. coli testing helps determine whether drinking water may have been exposed to bacterial contamination. These tests are particularly important for private wells because groundwater can become contaminated after flooding, well damage, septic problems, surface-water intrusion, or other changes around the property.
Total coliform bacteria are primarily used as an indicator of the sanitary condition of a water system. Finding total coliform does not automatically mean that disease-causing organisms are present, but it can indicate a pathway through which contamination entered the water. E. coli is more concerning because its presence can indicate fecal contamination.
Unlike minerals that mainly affect appearance or plumbing, bacterial results may require immediate attention. A positive result should be interpreted according to the organism detected and the laboratory or local health authority’s recommendations rather than assuming that all coliform findings carry the same level of risk.
Action: If E. coli is detected, avoid drinking the water until you have received appropriate guidance, addressed the source of contamination, and confirmed the water is safe through follow-up testing.
Nitrate occurs naturally in the environment, but elevated concentrations can enter groundwater from fertilizers, agricultural runoff, animal waste, and septic systems. This makes nitrate an especially useful parameter for private wells near farms, livestock areas, or septic systems.
EPA’s drinking-water standard for nitrate is 10 milligrams per liter measured as nitrogen. Concentrations above this level are particularly concerning for infants, because high nitrate exposure can interfere with the blood’s ability to carry oxygen. EPA specifically advises against using well water containing more than 10 mg/L nitrate to prepare infant formula or food.
Nitrate usually cannot be identified by looking at, smelling, or tasting the water. A clear glass of water can therefore contain elevated nitrate without giving the homeowner any obvious warning.
Action: If a test exceeds 10 mg/L nitrate as nitrogen, do not use the water for infant formula and consult a qualified water professional or local health authority about treatment and an alternative drinking-water source.
Lead is different from many groundwater contaminants because it often enters drinking water after the water reaches the property. Lead service lines, older plumbing, solder, fixtures, and corrosion can all contribute to lead at the tap.
Lead testing intended to evaluate household plumbing commonly uses water that has been sitting in the plumbing for several hours rather than a sample collected after prolonged flushing. EPA’s tap-monitoring requirements use first-liter samples after at least six hours of stagnation, with additional sampling requirements for properties served by lead service lines.
EPA’s health-based Maximum Contaminant Level Goal for lead is zero because there is no known safe level of lead exposure. As of 2026, the federal Lead and Copper Rule still uses a 15-parts-per-billion action level for determining when public water systems must take certain actions, while newer Lead and Copper Rule Improvements introduce additional requirements and a lower action level on a future implementation schedule.
A homeowner should therefore not interpret a result below 15 ppb as meaning that lead exposure is desirable or completely risk-free.
Action: If lead is detected, discuss the concentration and likely source with the laboratory or a water-treatment professional and take practical steps to reduce exposure, particularly for children and pregnant people.
Arsenic is a naturally occurring element that can dissolve into groundwater from surrounding rock and soil. It is particularly important for private-well owners because concentrations can vary substantially between locations and even between nearby wells.
Long-term exposure to elevated arsenic in drinking water has been associated with serious health effects. The EPA Maximum Contaminant Level for arsenic in public drinking water is 10 parts per billion, or 0.010 mg/L.
Like nitrate and lead, arsenic generally does not show itself through an unusual color, smell, or taste. Testing is necessary to determine whether it is present and at what concentration.
The appropriate treatment depends on the arsenic concentration and the rest of the water chemistry. That is one reason a complete laboratory analysis can be more useful than choosing a treatment system based on one contaminant alone.
Action: If arsenic is above 10 ppb, do not rely on boiling to remove it. Review the result with a water-quality professional and determine which treatment method is appropriate for your water chemistry.
Per- and polyfluoroalkyl substances, or PFAS, are a large family of persistent synthetic chemicals. They have been used in products and processes involving stain resistance, water resistance, firefighting foams, and industrial applications. Contamination has been identified near some military installations, airports, industrial facilities, landfills, and firefighting-training areas.
PFAS testing requires laboratory methods capable of detecting concentrations measured in parts per trillion. EPA established federal drinking-water standards for several PFAS in 2024, including Maximum Contaminant Levels of 4.0 ppt each for PFOA and PFOS. EPA’s health-based goals for PFOA and PFOS are zero.
Because PFAS comprises thousands of compounds, a result also needs to be interpreted according to which specific compounds the laboratory analyzed. Testing for one or two PFAS is not equivalent to screening for every chemical in the broader PFAS family.
ETR’s standard Basic, Premium, and Ultimate water panels do not currently include PFAS. ETR offers a separate PFAS drinking-water analysis that screens for 18 compounds, so homeowners who want both broad water-quality testing and PFAS analysis may need to combine tests.
Action: If PFAS is a concern because of your location, nearby land use, or previous water results, choose a test that clearly states which PFAS compounds are included rather than assuming they are part of every general water panel.
Radon is a naturally occurring radioactive gas produced as uranium in soil and rock breaks down. Most people associate radon with indoor air, but homes supplied by groundwater can also receive radon through their water.
When radon-containing water is used for showering, washing dishes, or other household activities, some of the gas can move from the water into indoor air. That makes radon-in-water testing different from a standard indoor-air radon test: the two evaluate related but separate exposure pathways.
Groundwater sources, including private wells, are generally more likely to contain radon than surface-water sources because groundwater remains in direct contact with radon-producing rocks and soil.
Action: If your home uses a private well in an area where radon is common, consider testing both the home’s air and water rather than assuming one result represents both.
Iron and manganese occur naturally in soil and rock and are common findings in groundwater. Unlike lead or arsenic, they are often noticed first because of what they do to the home rather than because someone experiences an immediate health effect.
Excess iron can produce rusty or reddish staining, sediment, or a metallic taste. Manganese may create darker brown or black staining. Both can accumulate in fixtures, plumbing, and water-using appliances.
EPA lists iron and manganese under its National Secondary Drinking Water Regulations, which address contaminants associated primarily with aesthetic, cosmetic, or technical water-quality problems. The federal secondary standards are 0.3 mg/L for iron and 0.05 mg/L for manganese. Secondary standards are generally guidelines rather than federally enforceable health limits.
Action: If staining, sediment, or metallic taste is a recurring problem, test the water before purchasing filtration equipment so you know whether iron, manganese, or another water-quality issue is responsible.
Hardness describes the concentration of dissolved minerals in water, particularly calcium and magnesium. Hard water is generally not considered a health problem, but it can become a very practical household problem.
As water is heated or evaporates, minerals can form scale on faucets, showerheads, heating elements, pipes, and appliances. Homeowners may also notice white spotting on dishes, less efficient soap lathering, or recurring mineral deposits around fixtures. Over time, heavy scale can reduce the efficiency and useful life of some water-using equipment.
Testing hardness gives you an actual measurement rather than forcing you to judge the problem from visible scale alone. That matters when sizing or programming a water softener because treatment requirements depend on the measured hardness level.
Action: If scale is building up around fixtures or appliances, test hardness before selecting or adjusting a water softener.
pH measures how acidic or alkaline water is. Although pH itself is not usually the contaminant homeowners are worried about, it can influence how the water behaves throughout the plumbing system.
Water with a low pH can be corrosive, which may increase the potential for metals from plumbing materials to enter the water. Higher pH can contribute to deposits and other aesthetic issues. This means pH can help explain why a home has corrosion, metallic taste, staining, or certain treatment problems even when pH is not the primary health concern.
EPA’s recommended secondary range for drinking-water pH is 6.5 to 8.5. Because this is a secondary rather than primary drinking-water standard, it is primarily used to manage aesthetic and technical water-quality concerns.
Action: If a test shows unusually low or high pH, interpret it alongside metals, alkalinity, hardness, and other water-chemistry results before deciding how to treat the water.
Total dissolved solids, usually shortened to TDS, measures the combined concentration of dissolved substances in water. These can include minerals, salts, metals, and other inorganic material.
TDS is therefore a general indicator rather than a test for one specific contaminant. A high result tells you that the water contains a relatively large amount of dissolved material, but it does not tell you which substance is responsible or whether the cause presents a health risk. More specific laboratory testing is needed to answer those questions.
High TDS can be associated with mineral deposits, salty or unusual taste, staining, and other aesthetic problems. EPA lists 500 mg/L as its secondary standard for TDS.
TDS meters can be useful for tracking broad changes in water chemistry, but they are not substitutes for laboratory contaminant testing. Two water samples can have similar TDS readings while containing very different dissolved substances.
Action: Treat an elevated TDS result as a signal to investigate the water chemistry further rather than as a diagnosis by itself.
Volatile organic compounds are carbon-based chemicals that can enter water from fuels, solvents, industrial processes, landfills, leaking storage tanks, dry-cleaning operations, and other sources. Examples include compounds such as benzene, toluene, trichloroethylene, and tetrachloroethylene.
A VOC problem may be especially relevant when a well is close to a gas station, industrial property, dry cleaner, landfill, or a site with a known history of chemical use or spills. However, the absence of a noticeable chemical smell does not rule contamination out.
Laboratories commonly analyze VOCs with specialized instrumentation such as gas chromatography combined with methods that can identify and quantify individual organic compounds at low concentrations. This is fundamentally different from a simple field measurement such as pH or conductivity.
ETR’s Premium and Ultimate water tests include VOC screening, while our Basic panel focuses on a smaller set of substances.
Action: Consider VOC testing when the property’s location or environmental history creates a plausible chemical-contamination risk, even if the water looks and smells normal.
Legionella is a type of bacteria that can grow within building water systems under favorable conditions. It is different from the routine coliform and E. coli testing commonly used to evaluate the sanitary condition of private wells.
The concern becomes greater in complex plumbing systems where water can remain stagnant or move slowly, disinfectant levels can fall, or temperatures allow bacteria to multiply. CDC identifies slow or absent water movement, biofilm, insufficient disinfectant, and certain water temperatures as factors that encourage Legionella growth.
For this reason, Legionella testing is more commonly associated with building water-management programs, healthcare facilities, hotels, large residential buildings, and systems that have experienced extended periods of low occupancy or stagnation. It is not necessarily part of every homeowner’s routine annual water test.
Action: Consider Legionella testing when the building or plumbing system has specific risk factors, rather than treating it as interchangeable with ordinary well-water bacteria testing.
The 12 parameters above are individual measurements and contaminants a laboratory may analyze, but water testing can also be organized into broader categories. These physical, chemical, and biological water parameters help group related characteristics and contaminants according to what they measure and how they affect water quality. Industrial water testing commonly considers these broader categories as well.
The physical parameter pertains to the general characteristics of the water that is used in an industrial setting. Factors such as temperature, color, odor, taste, turbidity, pH level, conductivity, and dissolved solids can comprise testing of the physical parameter. Each can impact water usage, so they must be observed to make sure these qualities fall within the preferred range for the industry that will use the water.
The primary concern with the inorganic and chemical testing parameter is the relative hardness or softness of the water. Hardness refers to the amount of inorganic mineral content found in the water. This can impact usage dramatically if used in manufacturing. For example, hard water will not as readily accept dissolved substances and can lead to deposits on plumbing and equipment given its high mineral content. This parameter involves testing for the concentrations of fluoride, magnesium, chloride, sulfate, calcium, nitrate, and phosphate.
Some metals are toxic if consumed through water, and in industries in which water will make its way into medicine or the food supply, they can be a concern. The toxic metal testing parameter pertains to the presence of substances in water such as copper, chromium, cadmium, zinc, lead, mercury, iron, and manganese.
Another parameter that is commonly used in industrial water testing is the organic, nutrient, and demand parameter. This is the analysis of water to determine the presence of substances such as phenols, oil, grease, pesticides and nitrate. Dissolved oxygen is another component of this parameter, so testing includes calculation of biochemical oxygen demand or BOD, as well as chemical oxygen demand or COD.
In any industry that involves the manufacture of food or medicine, the bacteriological parameter is key. This parameter involves the testing of water to determine the presence of fecal coliform and assesses the total coliform load.
The biological water testing parameter is primarily concerned with the presence of phytoplankton and zooplankton. Both can impact water quality and are of particular importance to any industry that is manufacturing consumables such as food, beverages, or medicines. They not only pose a quality control issue but can also cause health issues as well.
While rare, radioactive substances can be found even in groundwater that may be used for industrial purposes. While there can be other sources of contamination that are manmade in their origin, the primary course of radioactivity in groundwater comes via radon gas. The naturally occurring gas that forms from decaying uranium can permeate groundwater and could be a concern in some industries because of the associated health risks.
Industrial testing labs can be vital in ensuring the sanctity of water used in industry by applying a versatile and thorough set of parameters to assess water purity and associated problems. To learn more about industrial water testing and the parameters involved, visit Environmental Testing and Research Laboratories at https://etrlabs.com/industrial-testing/.
Individual results become much more useful when they are interpreted together. A low pH result, for example, may help explain why lead or copper is appearing in tap water. Elevated hardness can make scale problems easier to understand, while nitrate and bacterial findings together may point toward a possible septic or surface-contamination issue.
This is why broad water panels generally include multiple groups of analytes rather than treating every parameter as a completely separate problem. ETR currently offers several levels of testing depending on how much coverage a homeowner needs. Our Basic Water Test screens 53 substances, while our Premium and Ultimate tests expand the analysis to 113 and 249 substances respectively.
Not every specialized contaminant is automatically included, however. PFAS requires ETR’s separate 18-compound PFAS test. The exact substances included should therefore be checked before ordering rather than assuming that the word “comprehensive” means every possible water contaminant.
No. The appropriate testing schedule depends on your water source, previous results, property conditions, location, and reason for testing. Someone establishing a baseline for a newly purchased home may benefit from broader testing than a homeowner monitoring a known water-quality issue from year to year.
At ETR, we recommend our Premium Water Test for a first test and suggest repeating testing annually or whenever you notice a meaningful change in the water’s taste, odor, or appearance. More targeted testing may also make sense after flooding, well repairs, nearby construction, a contamination event, or a previous abnormal result.
Specialized contaminants should be added when the risk justifies them. For example, PFAS testing may make sense near known industrial or firefighting sources, while Legionella testing generally applies to different building-water risks than routine well testing.
There is not one simple answer that applies to every item on the list. EPA’s health-based Maximum Contaminant Level Goal for lead is zero, and the agency also established zero health-based goals for PFOA and PFOS. E. coli in drinking water is likewise a finding that warrants immediate attention because it can indicate fecal contamination.
Total coliform should not be described in exactly the same way as E. coli, however. Total coliform is primarily an indicator organism, so a positive result requires interpretation and follow-up testing rather than automatically proving that the water contains a disease-causing organism.
The important distinction is between a health-based contaminant limit, an action level, a secondary aesthetic guideline, and an indicator result. A laboratory report can help identify the number, but understanding what kind of standard applies tells you what that number actually means.
Water can look clear and taste normal while still containing bacteria, nitrate, lead, arsenic, PFAS, VOCs, radon, or other contaminants that require laboratory analysis to detect. At the same time, problems such as hard water, staining, corrosion, or scale can often be explained only after several water quality parameters are considered together.
ETR Laboratories offers testing options for both well and city water, from baseline panels covering bacteria, metals, minerals, hardness, and radon to broader panels that add VOCs and other contaminants. Specialized PFAS testing is also available separately for homeowners who need it.
Rather than guessing from taste, odor, or appearance, choose a test based on your water source, property, and specific risks. A laboratory analysis gives you the information you need to understand what is in your water and what, if anything, needs to happen next.
Most people who order a water test never see what
From the Lab by ETR Laboratories Most people treat bottled
City water and private well water are managed differently, so
Related Post.
Inside the ETR Laboratory: How Samples Are Analyzed
Most people who order a water test never see what happens after they mail the
Home Water Filtration Systems Often Pay for Themselves. Here Is the Math.
From the Lab by ETR Laboratories Most people treat bottled water as a small household
City Water vs Well Water: Different Tests, Different Risks
City water and private well water are managed differently, so the reasons you may want
What Comes in an ETR Water Test Kit: A Full Breakdown
When your ETR Lab’s water test kit arrives, the first question is usually simple: what’s
How ETR Laboratories Tests Your Water, Step by Step
Water testing ads usually talk about the kit in your mailbox. The part that decides
Water Test Panel Guide: Basic, Premium, or Ultimate?
Ordering a water test sounds simple until you see the options. One lab sells Basic,
How to Get Your Well Tested Without a Local Lab Nearby
You searched for a well water testing lab nearby and found nothing. Maybe nothing was
Michigan Well Water Testing Requirements: What to Know
Michigan requires testing when a private residential well is constructed, and state guidance calls for
Why Free Water Tests From Softener Companies Are Not Free
A free test a salesperson performs in your kitchen is a sales demonstration. It differs
12 Questions to Ask Before You Pay for a Water Test
Search for advice on what to ask before hiring a water company, and most of
Water Filters That Actually Remove PFAS: A Lab Guide
Every filter box on the shelf claims to handle PFAS these days, but that claim
Legionella Testing for Building Water Systems: A Full Guide
Everyone expects you to already have a water management program running. An outbreak would end