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Lead and Copper Sequential Sampling

The City of Flint is collecting sequential samples from six sites throughout the distribution system. These samples are collected weekly using two 250 milliliter (mL) sample bottles followed by ten 1 liter (L) bottles.

A faucet next to 2 250mL bottles and 10 1L bottles, representing sequential sampling

What is Sequential Sampling?

Diagram of a home and plumbing entering from the street; sample bottles are along the plumbing

A building's plumbing system and water service line (pipes) can be made up of different types of materials. Each type of material can affect drinking water differently, so it is useful to conduct what is known as "sequential sampling." Sequential sampling is where all water usage in a building is stopped for a minimum of six hours, known as "stagnation."

Next, water is collected from the faucet in a series of bottles. This is done without wasting any water or running the water before filling the bottles.

The first few bottles represent water that was in contact with the faucet or building plumbing during stagnation.

The later bottles represent water that was in contact with the water service line. These sample results can help decide whether treatment is working.

*Rows that appear empty have only been tested for aluminum (Al) and manganese (Mn).

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