Interpreting Your Water Test Report
Thousands of water well and spring owners get their drinking water tested through Penn State each year. This video explains all of the information on your water test report so you can make proper management decisions about your drinking water supply.
- [Bryan] Hi, my name's Bryan Swistock.
I'd like to take a few minutes to go over what's in each Penn State Water Test Report to help you interpret what your results mean.
First, congratulations on getting your water tested.
Our surveys have shown that only about half of the private water supplies in Pennsylvania have been properly tested by a state accredited lab.
Use of state accredited labs like the Penn State Agriculture Analytical Services Lab is vital to ensure that you get accurate and unbiased results.
We suggest that all private water system owners consider testing their water annually for coliform bacteria, and E. coli bacteria.
Other tests like pH and total dissolved solids should also be done every few years.
Your water test results include the table similar to the one shown here.
You may have more than one page of results, depending on how many tests you ordered from the lab.
You also received the page that provides a brief description of each of the tests on your report.
If any of your results were above the drinking water standards, you may have also received fact sheets for those parameters.
At the end of this short video, I'll provide a link where you can find fact sheets on most of the parameters on your report if you have questions or need more information.
Let's walk through an example test report so you can understand what each part of the report contains.
The top of the report contains the sample information including your contact information, the lab ID number for your sample, the dates and times the sample was collected, and the county where the water supply is located.
The sample type designates this as a drinking water sample.
The first column provides the analysis, which lists the various water parameters that you asked the lab to test in your water.
Your list may include only one analysis or it could include over a dozen different analyses, such as, the example shown here.
The second column provides the units for each analysis.
Bacteria units are in MPN per 100 milliliters, which stands for the most probably number of bacteria in 100 milliliters of water.
pH has no units, but most other parameters have units of milligrams in one liter of water.
One milligram per liter is equivalent to just four drops in a 55 gallon drum of water, so you can see that these tests are measuring extremely small amounts of these pollutants in water.
The small concentrations further emphasize why it's important to use state accredited labs that are carefully certified to make sure they are providing accurate and reliable results.
The third column has the most important information on the report, the actual results found for your water supply for each analysis.
For example, on this report the water was found to have 32 colonies of coliform bacteria per 100 milliliters of water.
You may also notice that some of your results have a less than sign in front of the number like the arsenic result on this result.
Labs do not report zeros on the reports because their instruments can only read down to a very lower number known as the detection level.
So, when none of the pollutant is found in the water, the lab reports it as less than the detection level.
In the case of arsenic here, no arsenic was found so the lab reported it as less than 0.003 milligrams per liter, which is the lowest amount of arsenic the lab instrument can read.
It's also possible that you might see a greater than sign in front of the number for your total coliform bacteria or E. coli bacteria.
The greater than sign indicates that a very high level of bacteria was found, above the maximum amount that can be measured by the lab.
For example, you might see a bacteria result of greater than 201, which indicates more than 201 colonies of bacteria were found in each 100 milliliters of water.
The next two columns provide the federal and state drinking water standards, and the type of standard.
Drinking water standards are developed each year because the pollutant causes health problems, or because the pollutant causes taste, stains, or other aesthetic problems.
On this report, we see that total coliform bacteria has a health based drinking water standard of zero colonies per 100 milliliters, so any measurable amount of coliform bacteria would represent a potential health problem.
Conversely the drinking water standard for total dissolves solids of 500 milligrams per liter is only because levels about 500 may cause taste or stains that make the water aesthetically unpleasing to use for drinking purposes.
You also notice that some parameters have no drinking water standards at all.
The final column on the report shows the standard method or EPA method that was used to test your water for each analysis.
These methods are required as part of the state lab accreditation program.
Below the table of results you will see a summary showing which if any of the analyses violated a drinking water standard.
There will also be contact information for an extension water resources educator, who could help answer questions you have about your drinking water test report.
Let's talk briefly about a couple of the most common water tests.
The most common are the total coliform bacteria and E. coli bacteria tests that are included in all of the water test packages.
This report you can see that the total coliform bacteria result was 32 colonies per 100 milliliters, while the E. coli bacteria result was two colonies per 100 milliliters.
Both of these results are above the drinking water standard of zero colonies, and both represent a health concern.
These generally harmless bacteria are tested in water as indicator bacteria, that should not be present in drinking water because they indicate that a pathway exists for harmful bacteria to enter your drinking water.
Most coliform bacteria come from surface water entering a well or spring, while E. coli bacteria indicate animal waste or human sewage is entering the water supply.
Possible health symptoms from these bacteria would be gastrointestinal illnesses including nausea, vomiting, and fever.
Another common water test is pH.
Drinking water should have a pH within a range of 6.5 to 8.5.
In this example, the water has an ideal pH of 7.01.
pH of water is mostly controlled by the type of rock that the well or spring originates from.
If your water has a pH below the 6.5 lower drinking water standard, it may be more corrosive to metals in your plumbing system.
A pH above the upper drinking water standard of 8.5 may cause the water to taste bad.
An important reason to test pH often is to compare it over time to make sure the water is not changing.
pH is a good overall indicator of water quality that should not change dramatically over time.
Total dissolved solids or TDS is another common test included in most test packages.
In this case, the TDS level of 56 milligrams per liter is well below the aesthetic drinking water standard of 500 milligrams per liter, so it easily passes the test.
Total dissolved solids is a measure of all the dissolved ions in your water including nitrate hardness, lead, arsenic, and many other pollutants.
High levels of TDS can be natural from certain types or rock, or can be various polluting activities.
The aesthetic drinking water standard of 500 milligrams per liter was set because this amount of TDS or higher can cause bad taste or staining.
TDS is an inexpensive and easy water test that should be monitored over time to make sure nothing is being added to your water from nearby activities.
Let's look quickly at two more tests on this example report.
Here we see that the corrosivity index is negative 1.76, indicating corrosive water.
In this case, anything below negative 0.5 is considered corrosive water, which could corrode metals in your plumbing system.
This example water test report includes several other important analyses, such as, arsenic.
In this case, the arsenic result was less than 0.003 milligrams per liter, while the health based drinking water standard is 0.10 milligrams per liter.
Since the result is far below the drinking water standard, this water supply passes this test and is considered safe to drink with respect to arsenic.
Many home owners wonder how their water compares with typical water test results across Pennsylvania.
Data from thousands of private wells and springs analyzed at Penn State show that many parameters are quite common.
For example, 33% have unsafe levels of coliform bacteria, 14% have unsafe levels of E. coli bacteria, 64% are considered corrosive, and 12% have unsafe levels of lead.
Overall, 40% of the private drinking water supply fail at least one health based drinking water standard and many more fail one of the aesthetic standards.
If you need more help understanding your drinking water test report, contact the water resources educator listed at the bottom of the report, or visit the Penn State extension drinking water website shown here.
This website also includes many fact sheets that provide tips on how various water quality problems can be treated or removed from drinking water.
Frequently Asked Questions