FAQ
Can Backflow Make You Sick? The Contaminants That Can Enter Your Water — and the Real Health Risks
Most people take for granted that the water coming out of their taps is safe to drink. And in most cases, it is — because multiple layers of protection stand between the water treatment plant and your glass. One of those critical layers is backflow prevention. When it fails, the consequences can range from bad-tasting water all the way to serious illness and, in documented historical cases, death. This guide explains exactly how backflow contamination occurs, which contaminants are most commonly involved, what health effects they can cause, and how a properly maintained backflow preventer protects you and your community.
For context on how and where these contamination pathways exist on your property, read our guide to what a cross-connection is and why it creates backflow risk.
How Backflow Contamination Actually Occurs
Backflow contamination occurs when a pressure reversal in the water distribution system draws non-potable water backward through an unprotected cross-connection and into the potable water supply. The event that triggers the pressure reversal — a water main break, a fire hydrant opening, a booster pump running at excessive pressure — may happen blocks away from your property. But if there’s an unprotected connection between your potable water line and a contamination source, the consequences can travel far. For a complete explanation of both contamination mechanisms, see our guide on back-pressure versus back-siphonage backflow.
The Contaminants Most Commonly Associated with Backflow
Pesticides and Fertilizers from Irrigation Systems
Irrigation system backflow is by far the most common source of residential backflow contamination in New Jersey. Lawn and garden irrigation systems draw from the same potable supply as your drinking water, and the lines sit in soil that may be saturated with fertilizer, herbicides, insecticides, and fungicides. During a back-siphonage event, these chemicals can be pulled into the domestic supply. Many pesticides are acutely toxic and can cause neurological symptoms at very low concentrations. Fertilizers, particularly nitrates, are associated with methemoglobinemia (‘blue baby syndrome’) in infants.
Bacteria and Pathogens from Irrigation Lines and Hoses
Standing water in irrigation lines between watering cycles becomes warm and stagnant — ideal conditions for bacterial growth. Legionella, E. coli, Pseudomonas, and other opportunistic pathogens can proliferate in these environments. During a backflow event, this bacteria-laden water can enter the potable supply, where it may reach immunocompromised individuals before any treatment can occur.
Pool and Spa Chemicals
Swimming pool makeup water connections are a common cross-connection in residential and commercial properties. Pool water contains chlorine at concentrations far above potable water standards, plus algaecides, pH adjusters, and stabilizers. Concentrated chlorine exposure causes respiratory irritation, mucous membrane damage, and potential toxicity. Additionally, pool water can harbor Cryptosporidium and Giardia, chlorine-resistant parasites that cause severe gastrointestinal illness.
Industrial and Commercial Chemicals
Commercial and industrial properties present some of the most serious backflow contamination risks. Chemical injection systems, cleaning equipment, plating baths, coolant systems, and process piping all create high-hazard cross-connections. Industrial chemicals that have been found in backflow contamination incidents include petroleum products, solvents, heavy metals, cleaning chemicals, and toxic process compounds. These exposures can cause acute poisoning, organ damage, and long-term health consequences.
Human Waste and Sewage
A sewer cross-connection — where a wastewater line and a potable water line are physically connected or in proximity with a potential failure mode — represents the most acute health hazard in any plumbing system. Sewage contamination introduces pathogens including Salmonella, Campylobacter, Norovirus, Rotavirus, Hepatitis A, and numerous other disease-causing organisms. Documented backflow incidents involving sewage cross-connections have caused gastroenteritis outbreaks affecting dozens to hundreds of people.
Fire Suppression System Water
Fire suppression system water is often stagnant for extended periods, may be treated with antifreeze agents in cold climates, and is not maintained to any potable water standard. Contamination from fire system backflow can introduce microorganisms, corrosion products, antifreeze compounds, and firefighting foam additives into the potable supply.
Heavy Metals from Corroded Piping
In some backflow scenarios, particularly those involving pressure surges that disturb settled pipe scale, backflow events can introduce lead, copper, and other heavy metals into the supply. Lead is a neurotoxin with no safe exposure level, particularly dangerous for children. Long-term exposure to elevated copper levels causes liver and kidney damage.
Documented Health Effects of Backflow Contamination
Backflow-related illnesses have been documented in numerous public health investigations across the United States and internationally. Common reported health outcomes include:
Gastrointestinal illness: Nausea, vomiting, diarrhea, abdominal cramps — the most frequently reported symptoms, caused by bacterial, viral, or parasitic contamination
Neurological symptoms: Headache, dizziness, confusion — associated with chemical contamination including pesticides and solvents
Respiratory effects: Coughing, irritation, breathing difficulty — associated with chemical contamination, particularly chlorine and industrial cleaners
Skin and eye irritation: Burns, rashes, conjunctivitis — from direct contact with chemically contaminated water
Severe acute poisoning: In documented cases involving industrial chemicals, backflow contamination has caused hospitalization and fatalities
Long-term organ damage: Chronic exposure to heavy metals or persistent organic pollutants from repeated low-level contamination events
Vulnerable Populations Face Greater Risk
While backflow contamination is dangerous for everyone, certain populations face substantially higher risk from even low-level exposure. These include infants and young children (still-developing immune and neurological systems), elderly individuals, immunocompromised people (transplant recipients, cancer patients, HIV-positive individuals), and pregnant women. In healthcare settings, backflow contamination can be catastrophic — which is why hospitals, dental offices, and dialysis centers are subject to the most stringent backflow prevention requirements in New Jersey.
Why Annual Testing Is the Critical Safeguard
A backflow preventer provides no protection if it isn’t working. The internal components of any backflow device degrade over time — springs weaken, rubber seals crack, check valve discs warp. A device that was certified last year may not be functioning today. This is precisely why New Jersey law requires annual certified testing: so that every single device is confirmed to be operational before the next pressure event occurs that might trigger a backflow. Read everything you need to know about how often backflow preventers must be tested in New Jersey.
If you’ve never had your device tested, don’t know when it was last tested, or have received a compliance notice, contact South Jersey Backflow immediately. The health consequences of a backflow event are never worth the cost of skipping an annual test.
South Jersey Backflow Protects Your Family and Community
Every annual backflow test we perform and every device we repair is part of protecting public health in New Jersey communities. South Jersey Backflow’s certified technicians serve all 21 New Jersey counties, providing professional backflow testing and certification service, backflow repair and rebuild service, and new device installations. Our work directly reduces the risk of the contamination events described in this article — and keeps your property in compliance with the regulations designed to prevent them. Visit our complete FAQ section or South Jersey Backflow Library for more educational content.
Schedule Your Backflow Service Anywhere in New Jersey
South Jersey Backflow has proudly served residential and commercial customers across all of New Jersey since 2004. Our certified technicians provide annual backflow testing and certification, expert repairs and rebuilds, and protective backflow enclosures — all with transparent pricing, complete paperwork handling, and 24/7 emergency availability. Call (856) 291-6809 or contact us online to get started today.