Consumers often ask the question, “OK, so my water is safe to drink according to my local Water Authority and a recent certified laboratory test, but why does it taste funny, smell bad and/or appear so cloudy?”

The answer to that question lies in something called Secondary Drinking Water Standards. The United States Environmental Protection Agency makes suggestions as to limitations for water parameters that do not necessarily pose health risks to humans, but can affect drinking water’s aesthetic properties (i.e. color, taste, odor, etc.).

If you need to test for any of the above items, we currently carry testing products for a number of them in the Water Test Kit Store (Shop.WaterTestingBlog.Com).

The United States Environmental Protection Agency requires public water companies, utilities, etc. to monitor and report specific water quality parameters on a regular basis. You can find the full list of those parameters here.

“National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water.” (source)

The government regulates the introduction of and requires the removal of items listed in the Primary Drinking Water Standards if they exceed Maximum Contaminant Levels (MCL’s) because scientists and health officials have concluded that overexposure to those items ingested via drinking water causes signifigant health risks in humans.

As always, when evaluating your drinking water for safety reasons, keep in mind that home water test kits work quite well as a screening tool in the field and that no one should rely colely upon the results of ANY field screening method when making the final determination as to whether or not they have safe drinking water.

A huge percentage of the general public does not know the difference between MCL, MCLG, MRDL and MRDLG. They ought not feel ashamed, though, because we took a short survey of people connected to water treatment, water testing, water processing, etc. and found that many of them had just as little knowledge on the topic as the general public.

Therefore we decided to visit the United States Environmental Protection Agency web site to find clear, concise definitions of MCL, MCLG, MRDL and MRDLG. See below:

Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

Maximum Residual Disinfectant Level (MRDL) – The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

( source )