Are cast iron pipe flakes in drinking water dangerous?

There may be a cast iron pipe that connects the city water main to your house's water supply. If that is the case then there is always the possibility of iron flakes getting into your drinking water. If your drinking water is clear when you look at it, then the cast iron flakes are so small that they cannot cause any issue. If your drinking water is a brownish color, then that could be iron flakes or even lead flakes. If you get brown water from your faucet, do not drink it. Contact your local water authority immediately to have the water tested.