Common Contaminants
The substances that come up most often in drinking water questions: what they are, where they come from and whether you would ever notice them.
Lead
Lead rarely comes from the water source itself. It typically enters drinking water through plumbing, including lead service lines, lead-based solder in older copper pipes, and certain brass faucets and fittings.
The EPA has set a health-based goal of zero for lead in drinking water, and the CDC states that no safe blood lead level has been identified for young children. Because lead has no taste, smell, or color, testing is the only way to determine whether it is present. Lead in tap water testing across NYC can help identify potential lead contamination in drinking water.
Lead levels can vary from one faucet to another and from one moment to the next, depending in part on how long water has been sitting in the pipes.
PFAS
PFAS are a large family of man-made chemicals used in non-stick coatings, stain-resistant fabrics, food packaging and some firefighting foams. They break down extremely slowly, which is why they are often called forever chemicals.
In April 2024 the EPA finalized the first national drinking water limits for several PFAS. In May 2026 the EPA proposed keeping the limits for PFOA and PFOS while extending the compliance deadline, and withdrawing the limits for some other PFAS. Because the rules are still changing, check the EPA’s PFAS page for the current status.
PFAS cannot be seen or tasted, and they require specialized laboratory methods to measure at the very low levels that matter.
Bacteria and Legionella
Laboratories commonly test for coliform bacteria and E. coli as indicators of possible contamination. Their presence suggests that a route may exist for contaminants from surface water or sewage to enter the supply, making these tests particularly important for private wells.
Legionella is different. It can grow in warm water inside building plumbing, hot water systems, and cooling towers. People can become ill by inhaling fine mist containing the bacteria, such as droplets released during a shower. This makes legionella drinking water testing in Queens relevant to assessing potential risks in buildings with complex hot water systems, where the conditions may support bacterial growth.
Nitrate
Nitrate reaches groundwater from fertilizers, manure and septic systems. It is mostly a concern for private wells in rural and suburban areas.
The federal limit for nitrate is 10 milligrams per liter (measured as nitrogen). High levels are particularly risky for infants under six months, which is why well water used to prepare formula should be tested.
How common contaminants compare
Many of the substances that matter most give no sign at the tap. This table summarizes where each one usually comes from and whether you might notice it.
| Contaminant | Common source | Can you notice it? | How it is checked |
|---|---|---|---|
| Lead | Service lines, solder, brass fixtures | No | Laboratory metals analysis |
| Copper | Copper pipes in corrosive water | Sometimes: blue-green staining, metallic taste | Laboratory metals analysis |
| PFAS | Industrial and consumer products | No | Specialized laboratory method |
| Coliform / E. coli | Surface runoff, septic systems | No | Microbiological culture |
| Legionella | Warm water in building plumbing | No | Specialized culture or PCR |
| Nitrate | Fertilizer, septic systems | No | Laboratory chemistry |
| Iron / manganese | Groundwater, older iron pipes | Yes: brown, orange or black staining | Laboratory metals analysis |
| Chlorine | Added as a disinfectant | Yes: smell and taste | Field or laboratory test |
Not sure which contaminants to test for?
Olympian Water Testing selects parameters through consultation, so the testing matches your water source and your concern.