How to Interpret a Water Analysis Report

This article outlines some of the major parameters you may see on the analysis and assists you in understanding the numbers on a water test report.
How to Interpret a Water Analysis Report - Articles


Whether your water causes illness, stains on plumbing, scaly deposits, or a bad taste, a water analysis identifies the problem and enables you to make knowledgeable decisions about water treatment.

Features of a Sample Report

Once the lab has completed testing your water, you will receive a report that looks similar to Figure 1. It will contain a list of contaminants tested, the concentrations, and, in some cases, highlight any problem contaminants. An important feature of the report is the units used to measure the contaminant level in your water. Milligrams per liter (mg/l) of water are used for substances like metals and nitrates. A milligram per liter is also equal to one part per million (ppm)--that is one part contaminant to one million parts water. About 0.03 of a teaspoon of sugar dissolved in a bathtub of water is an approximation of one ppm. For extremely toxic substances like pesticides, the units used are even smaller. In these cases, parts per billion (ppb) are used. Another unit found on some test reports is that used to measure radon--picocuries per liter. Some values like pH, hardness, conductance, and turbidity are reported in units specific to the test.

In addition to the test results, a lab may make notes on any contaminants that exceeded the PA DEP drinking water standards. For example, in Figure 1 the lab noted that total coliform bacteria and iron both exceeded the standards.

Retain your copy of the report in a safe place as a record of the quality of your water supply. If polluting activities such as mining occur in your area, you may need a record of past water quality to prove that your supply has been damaged.

Figure 1. A sample water analysis report.

Water test parameters

The following tables provide a general guideline to common water quality parameters that may appear on your water analysis report. The parameters are divided into three categories: health risk parameters, general indicators, and nuisance parameters. These guidelines are by no means exhaustive. However, they will provide you with acceptable limits and some information about symptoms, sources of the problem and effects.

Health Risk Parameters

The parameters in Table 1 are some commons ones that have known health effects. The table lists acceptable limits, potential health effects, and possible uses and sources of the contaminant.

Table 1: Standards, symptoms, and potential health effects of regulated contaminants.
ContaminantAcceptable LimitSources/UsesPotential Health Effects at
High Concentrations
* Recommended level in water at which remedial action should be taken. No mandatory standards have been set.
Atrazine3 ppb or. 003 ppmused as a herbicide; surface or ground water contamination from agricultural runoff or leachingheart and liver damage
Benzene5 ppb or. 005 ppmgasoline additive; usually from accidental oil spills, industrial uses, or landfillsblood disorders like aplasticaremia; immune system depression; acute exposure affects central nervous system causing dizziness, headaches; long term exposure increases cancer risks
Lead at tap0.015 ppm or 15 ppbused in batteries; lead gasolines and pipe solder; may be leached from brass faucets, lead caulking, lead pipes, and lead soldered jointsnervous disorders and mental impairment, especially in fetuses and infants; kidney damage; blood disorders and hypertension; low birth weights
Nitrates (NO3)10 mg/l (nitrate-N)
45 mg/l (nitrate)
soil by-product of agricultural fertilization; human and animal
waste leaching to groundwater
methemoglobinemaia (blue baby disease) in infants (birth to 6 months); low health threat to children and adults
Total Coliform<1 coliform/100 mlpossible bacterial or viral contamination from human sewage or animal manurediarrheal diseases, constant high level exposure can lead to cholera and hepatitis
Radon300 pCi/l*naturally occurring gas formed from uranium decay; can seep into well water from surrounding rocks and be released in the air as it leaves the faucetbreathing gas increases chances of lung cancer; may increase risk of stomach, colon and bladder cancers

General Water Quality Indicators

General Water Quality Indicators are parameters used to indicate the presence of harmful contaminants. Testing for indicators can eliminate costly tests for specific contaminants. Generally, if the indicator is present, the supply may contain the contaminant as well. For example, turbidity or the lack of clarity in a water sample usually indicates that bacteria may be present. The pH value is also considered a general water quality indicator. High or low pHs can indicate how corrosive water is. Corrosive water may further indicate that metals like lead or copper are being dissolved in the water as it passes through distribution pipes. Table 2 shows some of the common general indicators.

Table 2. General water quality indicators.
IndicatorAcceptable LimitIndication
pH value6.5 to 8.5An important overall measure of water quality, pH can alter corrosivity and solubility of contaminants. Low pH will cause pitting of pipes and fixtures or a metallic taste. This may indicate that metals are being dissolved. At high pH, the water will have a slippery feel or a soda taste.
Turbidity<5 NTUClarity of sample can indicate contamination.
Total Dissolved Solids
500 mg/lDissolved minerals like iron or manganese. High TDS also can indicate hardness (scaly deposits) or cause staining, or a salty, bitter taste.

Nuisance contaminants are a third category of contaminants. While these have no adverse health effects, they may make water unpallatable or reduce the effectiveness of soaps and detergents. Some nuisance contaminants also cause staining. Nuisance contaminants may include iron bacteria, hydrogen sulfide, and hardness. Table 3 shows some typical nuisance contaminants you may see on your water analysis report.

Table 3. Common nuisance contaminants and their effects.
ContaminantAcceptable LimitEffects
Chlorides250 mg/lsalty or brackish taste; corrosive; blackens and pits
stainless steel
Copper (Cu)1.3 mg/lblue-green stains on plumbing fixtures; bitter metallic taste
Iron (Fe)0.3 mg/lmetallic taste; discolored beverages; yellowish stains, stains laundry
Manganese (Mn)0.05 mg/l or 5 ppbblack stains on fixtures and laundry; bitter taste
Sulfates (SO4)250 mg/lgreasy feel, laxative effect
Iron Bacteriapresentorangeish to brownish slime in water

Hardness is one contaminant you will also commonly see on the report. Hard water is a purely aesthetic problem that causes soap and scaly deposits in plumbing and decreased cleaning action of soaps and detergents. Hard water can also cause scale buildup in hot water heaters and reduce their effective lifetime. Table 4 will help you interpret the hardness parameters cited on your analysis. Note that the units used in this table differ from those indicated in Figure 1. Hardness can be expressed by either mg/l or a grains per gallon (gpg). A gpg is used exclusively as a hardness unit and equals approximately 17 mg/l or ppm. Most people object to water falling in the "hard" or "very hard" categories in Table 4. However, as with all water treatment, you should carefully consider the advantages and disadvantages to softening before making a purchasing a water softener.

Table 4. Hardness classifications.
Concentration of hardness minerals
in grains per gallon (GPG)
Hardness Level
* level at which most people find hardness objectionable
below 1.0soft
1.0 to 3.5slightly hard
3.5 to 7.5moderately hard
7.5 ti 10.5*hard
10.5 and abovevery hard

Additional Resources

For more detailed information about water testing ask for publication Water Tests: What Do the Numbers Mean? at your local extension office or from this website.

Prepared by Paul D. Robillard, Assistant Professor of Agricultural Engineering, William E. Sharpe, Professor of Forest Hydrology and Bryan R. Swistock, Senior Extension Associate, Department of Ecosystem Science and Management