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Get Informed | What is Turbidity?

Turbidity is regulated under the secondary drinking water standard for aesthetic reasons and it is used as an operational control measure. Turbidity is commonly used as an indicator for the general condition of the drinking water, and is an easy field water-quality parameter to measure. Turbidity in water is caused by suspended matter such as clay, silt, and organic matter and by plankton or other microscopic organisms that interfere with the passage of light through the water (American Public Health Association, 1998). Turbidity is closely related to total suspended solids (TSS), but also includes plankton and other organisms. Turbidity of natural waters tends to increase during runoff events as a result of increased overland flow, stream flow, and erosion.

Turbidity, literally ‘dirty water,’ is the reduction of clarity in water due to the presence of suspended or colloidal particles. Turbidity is measured by the amount of light which is reflected by the particles back to a detector that is located at a 90 angle to the light path.

How Does Turbidity Become a problem?

Water with a high turbidity may cause aesthetic problems (it looks dirty) and can damage fixtures, appliances, and piping. It can also make it more difficult to effectively treat a water source for other contaminants.

What are the Health Risks for Turbidity?

Turbidity itself is not a major health concern, however, high turbidity can interfere with disinfection and water treatment processes and provide a medium for microbial growth and contamination. A water with an elevated turbidity may be associated with aesthetic problems and nuisances.

What are the Standards for Turbidity?

The U.S. Environmental Protection Agency’s (EPA) Surface Water Treatment Rule requires systems using surface water or groundwater under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that at no time can turbidity go above 5 nephelometric turbidity units (NTUs). Systems that filter must ensure that the turbidity goes no higher than 1 NTU (0.3 NTU for conventional or direct filtration) in at least 95% of the daily samples in any month. Because of the potential association of elevated particles with bacterial or microbiological contamination and other nuisance issues, an elevated level of turbidity at the time of sample or post-sampling can suggest a water quality problem.

Get Tested | Turbidity

Unlike many contaminants in drinking water, the turbidity in itself is not potentially hazardous. An elevated water turbidity is used as an indicator of a water-quality-related problem that could include the presence of settleable and non-settable materials like sand, silt, or clay, iron, manganese, rust, biofilms, chemical scale or precipitates, or corrosion by-products. Your best course of action is to document the observable conditions or problems with the water and learn more about your source, well construction, surrounding land-use, household piping, existing water treatment systems and local geology. If you do have a turbidity problem, there are water treatment technologies available now that can reduce or even eliminate the turbidity problem of your drinking water.

Note: Do not just test your water for Turbidity because there may be other primary and secondary drinking water contaminants that could be elevated in the water or conditions in the system contributing to the problem. It is also possible that the suspended particles themselves, such as corrosion by-products, could be harmful.

Level 1 | Observational Self-Testing

Observations for Turbidity

The symptoms for turbidity in the water include:

  • The drinking water appears cloudy or discolored at the time of sampling or the drinking water becomes cloudy following a major recharge (snow melt or rainfall) events.
  • The system uses a sediment or particle filter, the screens on fixtures are clogged, or the water appears discolored and the discoloration may or may not settle over time.
Try Our Level 1 Drinking Water Self-Diagnostic Tool
Have water issues? Answer our self-diagnosis questionnaire from your observations to get an initial diagnosis. Then follow our recommended steps to remediate your issue.
Self-Diagnostic Tool

Level 2 | Do-It-Yourself Water Testing

Level 2 Testing is Do-It-Yourself testing that can be done in your own home using a Testing Kit. After you’ve done Level 1 Testing, Level 2 Testing can confirm if your observations are correct. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment (see below) or continue to Level 3 Testing.

Notes on Level 2 Testing for Turbidity

Turbidity can be associated with the presence of suspended particles, oxidized particles, biological films, and chemical coatings. At a minimum, we would recommend the Health Metric In-Home DIY Drinking Water with TDS test below and that you make sure you complete a Level 1 Self-Diagnostic Analysis. If you conduct regular turbidity testing, we would recommend a turbidity meter.  We routinely use either the Sper Scientific, LaMotte, or Hach Turbidity Meters.

Recommended Level 2 Tests
CityCheck Standard

<div class="product-note in-L4-sulfur-treatment">Note: Use in combination with Sulfate-Reducing Bacteria Test</div>

WaterCheck® Standard

<div class="product-note in-L4-sulfur-treatment">Note: Use in combination with Sulfate-Reducing Bacteria Test</div>

Crystal Quest
SMART Whole-House Water Filter System

<div class="product-note in-L6-toluene">Note: If the concentration is less than 0.8 mg/L</div>


Level 3 | Informational Water Testing

Level 3 Testing is done through an accredited Water Testing Laboratory. With Level 3 Testing, you can order a testing kit that is used to prepare your sample and submit it to the lab. By utilizing a lab, you have the assurance that a certified water expert had analyzed your water sample. If your test results reveal the presence of a contaminant that is cause for concern, you can either proceed to determine the best treatment options (see below) or continue to Level 4 Testing - Certified Testing.

Notes on Level 3 Testing for Turbidity

Most quality informational water tests include testing for turbidity, but the turbidity of the water may change during the transport of the sample because of oxidation and the formation of metal oxides after the water has been sampled.

For well water sources and private systems, we recommend the National Testing Labs Standard Well Water Kit and for city water customers we recommend the National Testing Labs City Water Check Standard. If the discolored water looks like brown tea (colored by dissolved tannins), we suggest the Tap Score Essential Well Water Test or the National Testing Labs Tannins-in-water test.

Level 4 | Certified Water Testing

A Level 4 Certified Test Test uses chain-of-custody with a water professional coming to your home to prepare the water sample and then works with an accredited laboratory in order to certify your test results. This type of testing not only gives you the highest level of assurance in the accuracy of your test results, but can also be used as a document in legal cases. For Baseline Testing, we recommend that you use Certified Testing.

Notes on Level 4 Testing for Turbidity

In order to evaluate a turbidity problem for potable water, it is necessary to understand the source of the water and have some basic information on the general water quality to please complete the diagnostic analysis. It is best to measure turbidity in the field and not in the laboratory.

Get Treatment | Turbidity

For turbidity, the primary goal is to understand the cause or causes for the elevated turbidity. For common problems or situations, it may be possible to use a whole-house particle filter, but the size or capacity of the filter and the particle removal size-range is critical. Normal particle filtration systems need to have filters replaced or filters backwashed on a regular basis. Periodic testing should be maintained after the treatment system is in place to ensure objectives are being met and the system is operating properly. Most systems will require some form of maintenance every 3 months to 1 year.

Short Term Treatment

If it appears you are experiencing a problem with turbidity, it may be advisable to boil the water prior to use. Elevated turbidity commonly occurs when a water distribution system is being flushed or repaired. An interim solution may be the use of a point-of-use device, using a bottled water source, or hauling in potable water. Because other contaminants may be present in the water, it would be advisable to have the water tested before and after the use of any point-of-use device. And always test for microbiological quality.

Contact a KnowYourH2O Recommended Professional

Submit a Request for Consultation with the KnowYourH20 Team. Contact Us

Long Term Treatment

For the long-term, it may be necessary to install a water treatment system. For turbidity, the common water treatment technologies are backwashable particle filters, whole-house disposable particulate filter cartridges, and submicron point-of-use devices. Depending on the technology and the concentration of turbidity, the reason for the turbidity, and the presence other contaminants, the system may require a secondary or additional water treatment barrier.

Contact a KnowYourH2O Recommended Professional

Recommendation: Seek Advice from a Local Professional (Customized Solution). Contact Us

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