Nearly five years after the city of Flint, Michigan, confronted a contaminated water supply, lead in water continues to be a problem around the US.

There are many different contaminants that can be found in water, from E. coli to materials like iron or manganese. For the latest Verge Science video, we decided to focus on lead, which gets into our water a lot closer to home than you might think.

In New York City, where many of The Verge’s staff live, the city’s water quality is a point of pride. It gets regularly tested for contaminants as it makes its way from distant reservoirs to our pipes, and it has won awards and taste tests. This water doesn’t have lead when it enters the city’s water system, but some older buildings and homes in the city still have lead in service lines that connect to the main distribution lines, and tiny bits of lead can dissolve into the water there. The situation in NYC isn’t nearly as dire as in other parts of the country where lead levels that are higher than Flint’s can be found, but it is still a concern.

To combat the issue, cities like New York typically add phosphoric acid (also found in some sodas) to the water. The treatment coats the inside of those pipes with a protective layer of minerals, making it harder for the water to corrode the metal. In Flint, one of the issues in 2014 was that the replacement source of water didn’t get this anti-corrosion treatment, letting contaminants, including lead, leach into the water supply. But even treated water isn’t foolproof, and sometimes, lead can make its way into the water anyway.

Unlike disease-causing bacteria, boiling water doesn’t help eliminate lead’s threat. All that does is concentrate the toxic metal. Unlike manganese or iron, dissolved lead can’t be seen. Even tasteless and invisible, lead can still be harmful to people, particularly children.

When it comes to lead in the water supply, New York City has been addressing this particular problem in schools where there are still some buildings with lead fixtures. The city’s Department of Environmental Protection is running a public service campaign to try to reduce lead exposure in the city, focusing on both lead in water and lead paint.

While the government tackles the bigger picture, figuring out whether you have lead in your water takes some effort. If you are a New York City resident wondering if your water contains lead, the city offers a free lead testing service. There are also swarms of lead tests and filters available online or in hardware stores. (Experts recommend looking for the NSF 53 rating on filters if you’re looking to reduce lead in your water.)

For our latest Verge Science video, we looked into the different tests that are available to see how well some of them worked and what to do if you find out that you need to get the lead out.