Drinking water standards are rules that help keep your water safe to drink. These rules are part of water quality standards that control what can be in your tap water. They are designed to protect people from harmful substances in water, such as bacteria in the water supply, heavy metals in drinking water, and toxic chemicals.

In the United States, the United States Environmental Protection Agency (EPA) creates EPA drinking water regulations under the Safe Drinking Water Act (SDWA). This law, passed in 1974, is the main system that protects public water systems and ensures safe drinking water guidelines for millions of people.

These drinking water safety rules set clear limits on microbial, chemical, and radionuclide contaminants. The goal is simple: protect health and reduce the risk of waterborne diseases, gastrointestinal illness, and long-term harm, such as increased cancer risk from water contaminants.

Water quality compliance is important because water can contain many risks. Some common dangers include:

Lead in drinking water and copper in drinking water
Arsenic contamination of water and nitrate contamination
PFAS in drinking water and other emerging contaminants
Microplastics, water contamination, and viruses in drinking water

The EPA uses water quality criteria and health-based water limits to decide how much of each contaminant is safe. These limits are part of the National Primary Drinking Water Regulations (NPDWR) and the National Secondary Drinking Water Regulations (NSDWR).

To measure safety, experts use tools like:

Maximum contaminant level (MCL)
Maximum contaminant level goal (MCLG)
Treatment technique requirements

These help define enforceable water standards and secondary water standards, which guide how water is treated and tested.

Water quality is also checked using key water quality parameters such as:

pH level of drinking water
Turbidity water quality
Total dissolved solids (TDS)
Water clarity, water temperature standards, and water conductivity

What Are Drinking Water Standards?

Drinking water standards are rules that set safe limits for substances in water. These rules are part of the drinking water legislation and federal water regulations. They help ensure that water is safe to drink every day.

These standards are developed by the EPA Office of Water and supported by groups such as the Centers for Disease Control and Prevention (CDC) and the U.S. Geological Survey (USGS). They are also guided by global advice from the World Health Organization (WHO).

The main purpose of these standards is to:

Protect public health
Control biological contaminants and organic contaminants in water
Reduce toxic chemicals in water
Manage long-term exposure to contaminants

Under the Safe Drinking Water Act (SDWA), the EPA sets limits for more than 90 contaminants in public water systems (PWS). These include:

Inorganic contaminants like lead and arsenic
Organic contaminants like pesticides
Disinfectants in water, like chlorine
Disinfection byproducts DBPs
Microbial contaminants such as Giardia lamblia, Cryptosporidium, and Legionella
Radionuclides

These contaminants are grouped into six main categories:

Microorganisms
Disinfectants
Disinfection byproducts
Inorganic chemicals
Organic chemicals
Radionuclides

Each category has strict EPA contaminant limits based on public health water standards.

There are two main types of standards:

1. Primary Standards

These are legally enforceable standards that protect health. They include:

maximum contaminant level (MCL)
treatment technique (TT)

These rules ensure that public water systems follow safe limits for harmful substances.

2. Secondary Standards

These are aesthetic water standards that focus on:

taste
smell
color

They include limits for factors such as water hardness, alkalinity, and water color and odor.

Who Regulates Drinking Water in the US?

In the United States, drinking water standards are managed by a system of federal, state, and local agencies. This system ensures that public water systems comply with water quality standards and provide safe drinking water for everyone.

The Role of the Environmental Protection Agency (EPA)

The United States Environmental Protection Agency (EPA) is the main authority for EPA drinking water regulations. It works under the Safe Drinking Water Act (SDWA) to protect public health.

The EPA sets national drinking water rules
It creates limits for water contamination limits
It ensures water regulation compliance across the country

The EPA sets and enforces standards to limit harmful germs and chemicals in water

The EPA also develops National Primary Drinking Water Regulations (NPDWR). These rules regulate more than 90 contaminants, including lead, arsenic, and radionuclides.

These rules are based on public health water standards and use tools like:

Maximum contaminant level (MCL)
Maximum contaminant level goal (MCLG)
Treatment technique requirements

An MCL is the legal limit for a contaminant in drinking water

The Safe Drinking Water Act (SDWA)

The Safe Drinking Water Act (SDWA) is the primary law governing drinking water. It was passed in 1974 to protect people from unsafe water.

It gives the EPA the power to set health-based water limits
It applies to all public water systems (PWS)
It requires regular water monitoring systems and compliance monitoring

The SDWA is the key federal law for protecting public drinking water

This law also ensures:

Water quality reporting through Consumer Confidence Reports (CCR)
Tracking through the Safe Drinking Water Information System (SDWIS)
Evaluation of risks using risk assessment and exposure limits to water

The EPA also studies new risks using:

Contaminant Candidate List (CCL)
Unregulated Contaminant Monitoring Rule (UCMR)

These programs help identify emerging contaminants and guide future rules

State and Local Authorities

While the EPA sets federal water regulations, states and local agencies also play a big role.

States enforce drinking water safety rules
They manage water law enforcement and EPA programs

States often take primary enforcement responsibility under EPA oversight

State agencies also:

Run water quality testing methods
Conduct sanitary surveys of water systems
Manage water supply management

How the System Works Together

The US system works in layers:

Federal Level

EPA sets EPA water laws
Defines water quality criteria
Establishes enforceable water standards

State Level

Implements rules
Oversees public water system standards
Ensures water quality compliance

Local Level

Operates water treatment plants
Conducts drinking water sampling
Maintains water distribution systems

Types of Drinking Water Standards Explained

In the United States, drinking water standards are divided into two main types. These types help control water contamination and ensure water is safe and pleasant to use.

These standards are created by the United States Environmental Protection Agency (EPA) under the Safe Drinking Water Act (SDWA). They are part of the broader water quality standards that protect public health and ensure compliance with water quality requirements.

1. Primary Drinking Water Standards (Health-Based Rules)

Primary standards are the most important rules. They are legally enforceable standards that protect people from harmful substances.

They are part of the National Primary Drinking Water Regulations (NPDWR)
They apply to all public water systems
They control microbial contaminants, chemical contaminants, and radionuclides in water

These standards limit contaminants that can harm human health

Key Features

Use the maximum contaminant level (MCL) as the legal limit
Based on the maximum contaminant level goal (MCLG) for safety
Include treatment technique requirements when limits cannot be measured

An MCL is the highest level of a contaminant allowed in drinking water

Examples of Controlled Contaminants

Primary standards regulate many harmful substances, including:

Lead in drinking water and copper in drinking water
Arsenic contamination and nitrate contamination of water
Bacteria and viruses in water
PFAS in drinking water and other emerging contaminants

These limits help reduce:

Waterborne diseases
Gastrointestinal illness water
Long-term exposure to contaminants
Cancer risk from water contaminants

2. Secondary Drinking Water Standards (Aesthetic Rules)

Secondary standards are different. They are non-enforceable water standards that focus on how water looks, smells, and tastes.

They are part of the National Secondary Drinking Water Regulations (NSDWR)
They guide public water system standards, but they are not mandatory

These standards are guidelines for taste, odor, and color, not health risks

What They Control

Secondary standards manage:

Color and odor of the water
Hardness of water
Alkalinity water
Total dissolved solids (TDS)

These are called aesthetic water standards because they affect comfort rather than safety.

Why They Matter

Even if water is safe, it may still:

taste bad
smell unpleasant
look cloudy

Secondary standards help improve water clarity, water temperature, and the overall user experience.

How Both Standards Work Together

Both types of standards support potable water standards and ensure safe water.

Primary Standards

Protect health
Set health-based water limits
Required by law

Secondary Standards

Improve taste and appearance
Provide secondary water standards
Act as guidance

Together, they help maintain:

Water quality criteria
Water safety risk assessment
Water infrastructure safety

What Is a Maximum Contaminant Level (MCL)?

A Maximum Contaminant Level (MCL) is one of the most important parts of drinking water standards. It tells us how much of a harmful substance is allowed in drinking water.

In simple words, an MCL is the highest level of a contaminant that can be in water and still be considered safe.

Simple Definition

An MCL is a legal limit set by the United States Environmental Protection Agency (EPA)
It applies to all public water systems (PWS)
It is part of the EPA drinking water regulations under the Safe Drinking Water Act (SDWA)

An MCL is the legal threshold for contaminants in drinking water

How MCL Works

To set an MCL, the EPA follows a step-by-step process:

Step 1: Set a Safe Goal (MCLG)

The maximum contaminant level goal (MCLG) is the level with no known health risk
It includes a safety margin for protection

Step 2: Set the Legal Limit (MCL)

The EPA sets the MCL as close as possible to the MCLG
It considers:
- available technology
- cost
- ability to measure the contaminant

MCLs are based on safety goals but also consider real-world limits

What Happens If MCL Is Exceeded?

If water goes above the MCL, the system must act fast:

Notify the public
Fix the problem
Improve water treatment plants or filtration systems for water
Increase water monitoring systems

This is part of water regulation compliance and ensures water quality compliance.

MCL vs MCLG (Easy Comparison)

Here is the replacement table comparing the Maximum Contaminant Level Goal (MCLG) and the Maximum Contaminant Level (MCL):

Term	Meaning	Enforceable
MCLG	Ideal safe level with no health risk	No
MCL	Legal limit allowed in water. It is the legal threshold for contaminants in drinking water.	Yes

What Contaminants Are Regulated?

In the United States, drinking water standards regulate many harmful substances, or contaminants. These are things that can get into water and affect your health.

The United States Environmental Protection Agency (EPA) regulates 90+ contaminants under the Safe Drinking Water Act (SDWA) to protect public water systems.

These contaminants are grouped into clear categories to support compliance with water quality standards.

The 6 Main Categories of Contaminants

The EPA organizes contaminants into six groups based on risk and type.

1. Microorganisms

These are tiny living organisms that can cause illness.

Bacteria in the water supply
Viruses in drinking water
Parasites like Giardia lamblia and Cryptosporidium

These are the most common causes of waterborne diseases and gastrointestinal illness.

2. Disinfectants

These are chemicals added to water to kill germs.

Chlorine disinfectant water
Chloramine

They are safe at low levels but still controlled under EPA contaminant limits.

3. Disinfection Byproducts (DBPs)

These form when disinfectants react with natural materials.

Disinfection byproducts DBPs
Trihalomethanes

These are among the chemical contaminants in drinking water and are linked to long-term exposure.

4. Inorganic Chemicals

These are minerals or metals that can be harmful in high amounts.

Lead in drinking water
Arsenic contamination of water
Nitrate contamination
Copper in drinking water

These can cause serious problems like neurological disorders and infant health issues.

5. Organic Chemicals

These come from human activity, like farming and industry.

Pesticides and herbicides
Industrial chemicals
Fuel residues

Many are linked to cancer risk, water contaminants, and environmental pollution.

6. Radionuclides

These are radioactive elements found in soil and rocks.

Uranium
Radium

These are regulated due to long-term health risks like cancer.

Emerging Contaminants You Should Know

Some contaminants are not yet fully regulated but are under study.

PFAS in drinking water
Microplastics water contamination
Pharmaceuticals

The EPA tracks these using the Contaminant Candidate List (CCL) and may regulate them in the future.

How Drinking Water Is Tested and Monitored

To keep water safe, drinking water standards require regular testing and monitoring. This process ensures that public water systems comply with EPA drinking water regulations and meet water quality standards.

The United States Environmental Protection Agency (EPA) sets clear rules for water monitoring systems, testing methods, and reporting.

Why Testing and Monitoring Are Important

Testing helps detect harmful substances early. It supports:

Water quality compliance
Contaminant detection
Protection from waterborne diseases and toxic chemicals in water

Public water systems must meet health standards and perform regular monitoring and reporting.

How Drinking Water Is Tested

Water testing follows a simple but strict process.

Step 1: Drinking Water Sampling

Water is collected from different points in the system
Includes sources, treatment plants, and taps
Ensures accurate drinking water sampling

Step 2: Laboratory Water Analysis

Samples are tested in certified labs
Labs use approved methods for laboratory water analysis

Water systems must use EPA-approved methods to analyze samples.

These tests check for:

Microbial contaminants in water
Chemical contaminants in drinking water
Radionuclides in water

Step 3: Water Quality Testing Methods

Different water quality testing methods are used, such as:

Chemical testing
Microbial testing
Physical testing

These methods measure key water quality parameters, including:

pH level of drinking water
Turbidity water quality
Total dissolved solids (TDS)
Conductivity water
Water clarity

Step 4: Compliance Monitoring

After testing, the results are reviewed to ensure compliance with water regulations.

Compared with the maximum contaminant level (MCL)
Checked against health-based water limits
Reported to regulators

EPA and states review sample data to confirm standards are met.

Is Tap Water Safe in the US?

In most cases, tap water in the United States is safe to drink. This is because strict drinking water standards are set and enforced by the United States Environmental Protection Agency (EPA) under the Safe Drinking Water Act (SDWA).

The EPA sets limits for harmful substances and ensures water systems follow these rules

How Safe Is US Tap Water?

Over 92 percent of people served by community systems get water that meets all health-based standards
More than 90 percent of water systems follow EPA rules each year

This means most public water systems meet water quality standards and provide safe water.

Why Tap Water Is Generally Safe

US tap water is considered safe because:

The EPA regulates 90+ contaminants
Systems must follow maximum contaminant level (MCL) limits
Regular water monitoring systems and compliance monitoring are required

But Is It Always Perfect?

Even though water meets legal standards, there can still be concerns.

1. Aging Infrastructure

Old pipes can add lead in drinking water or copper to drinking water
Local issues can affect water distribution systems

2. Emerging Contaminants

Substances like PFAS in drinking water and microplastics in water contamination are still being studied
Some are not fully regulated yet

Millions of Americans may be exposed to unregulated chemicals in water

3. Differences by Location

Water quality can vary by city or region
Small systems may have more issues

Most violations happen in smaller or rural systems

What About Private Wells?

Private wells are not regulated by the EPA
Owners must do their own water quality testing methods

This means safety depends on regular testing by the owner

How to Know If Your Water Is Safe

You can check your water quality by:

Reading your Consumer Confidence Report (CCR)
Checking EPA data in the Safe Drinking Water Information System (SDWIS)
Testing your water at home

Water systems must share yearly reports with customers

Frequently Asked Questions (FAQs)

What are drinking water standards?

Drinking water standards are rules that control what can be in your water to keep it safe. The United States Environmental Protection Agency (EPA) sets these rules to limit harmful germs and chemicals in tap water and protect public health.

Who regulates drinking water in the US?

Drinking water in the US is regulated by the EPA under the Safe Drinking Water Act (SDWA). The EPA sets national standards, while states and local agencies help enforce them to make sure water systems follow the rules.

What is the Safe Drinking Water Act (SDWA)?

The Safe Drinking Water Act (SDWA) is the main law that protects public drinking water. It was passed in 1974 and gives the EPA the authority to set health-based standards for contaminants in water.

What is a Maximum Contaminant Level (MCL)?

A maximum contaminant level (MCL) is the legal limit for how much of a substance can be in drinking water. It is set by the EPA and applies to all public water systems to ensure water stays safe for people to use.

How many contaminants are regulated in US drinking water?

The EPA regulates more than 90 contaminants, including microorganisms, chemicals, and radionuclides. These are grouped into categories to help control different types of risks in drinking water.

What are primary and secondary drinking water standards?

Primary standards are enforceable rules that protect health by limiting harmful contaminants. Secondary standards are guidelines that focus on taste, smell, and appearance and are not required by law.

Is tap water safe in the US?

Yes, in most cases, tap water in the US is safe. About 9 out of 10 people get their water from public systems that must meet EPA safety standards and treat water to remove harmful substances.

Are private wells regulated?

Private wells are not regulated by the EPA. This means the owner is responsible for testing and maintaining water quality, since federal drinking water rules mainly apply to public systems.

How can I check the quality of my drinking water?

You can check your water quality by reading your local water report or using EPA tools. Public water systems must test water regularly and share results so you can see if it meets safety standards.

What are emerging contaminants in drinking water?

Emerging contaminants are new or less-regulated substances, such as certain chemicals, that may be found in water. The EPA studies these through programs like the Contaminant Candidate List to determine whether future rules are needed.