Cambridge MA water chlorine content

Used as a real-world reference point for the Delrin chlorine sensitivity — Cambridge water from Fresh Pond has 5–10 ppm chlorine, ten times the DuPont "corrosion resistant" threshold. EPA allows up to 100 ppm in potable water. Teaching point: nominally "potable" water spans two orders of magnitude in the variable that determines whether Delrin survives.

Now, how much chlorine is in the Cambridge water this morning, if you want to make coffee? It's basically rain water, but it comes out of Fresh Pond up here since the 1640s, and it has five or ten ppm chlorine. Really good water in the Northeast will be five or ten ppm chlorine — and DuPont says it's corrosion resistant to something that is ten times better than some of the better potable water. The EPA says you can have up to a hundred parts per million chlorine and it's still potable water. So if you're in San Antonio or Las Vegas, you could have seventy, eighty, ninety parts per million chlorine. Delrin is not so good.