When the water department (or fire department) flushes hydrants in your neighborhood, discoloration of your water and issues with pressure may occur — BUT for the most neither of the issues really ought not pose health risks.

Experts in the field do, of course, suggest letting faucets run to allow discoloration and any trapped air pockets to pass before collecting water for use, though.

Why flush hydrants?

Not all water lines in a system get equal use and that means sediment may have the ability to collect in less used lines. Over time that sediment could possibly build up to the point where it forms an obstruction. In the event of a fire that obstruction could stop much needed water from flowing through firemen’s hoses.

What is the discoloration?

Typically we have seen the discoloration come from rust formed in the pipes between the water treatment facility and the hydrant. Remember: The water typically contains chlorine (an oxidizer) and that water sits idle in metal pipes… so certainly rust can form over time.

As stated previously, the flushing of hydrants helps to keep that rust from building up in ways that would impair the water system’s flow rate.

Should I test my water for metals after hydrant flushing?

We have not heard of incidents where drinking water absolutely needed testing for metals after hydrant flushing but it does stand to reason (in our opinion) that a homeowner may want to test for things like metals (and possibly coliform bacteria) after any event that disrupts the water supply.

Do we have any Harvard Haters in the house today? If so, you will take great delight in the knowledge that students at Harvard University in Cambridge, Massachusetts got to cope with brown, dingy water from their faucets and in their toilets for a while recently.

And no, we don’t mean some MIT students, known rivals of the Harvard students, broke into the local water treatment plant and poured rust colored food coloring into the water supply.

Instead, members of the local fire department tested and flushed fire hydrants near one of the Harvard University housing units.

Hydrant testing may disturb the sediment that naturally occurs in the water piping system. Water from your faucets and toilet may appear rust colored from this disturbance. Rust discoloration may last for several hours after the tests have been completed. Discolored water does not usually present a health hazard, however; it is recommended that anyone who has doubts about the rust colored water should not drink it. If you do not have bottled water, you may wish to store tap water in your refrigerator for the day of the test.

We also suggest that dorm residents check their water before doing laundry because the discolored water may stain clothes. If you would like to know when the hydrants are being tested in your area, please review the schedule shown below or call the FMO Fire Safety Services at 617- 496-4075 for daily test locations. If you have any questions on water quality Jim Cullity at 617-894-6841. Locations: River Area | Date: Tuesday September 15, 2009 ( source )

“OK, but what if a person has rust colored drinking water at times other than when the fire department test and/or flushes the hydrants?”

Situations like that require immediate water testing and we suggest having the water analyzed by a certified water testing laboratory. If not possible to have that testing done right away we suggest at the very least testing the water with an at-home drinking water test kit.

When confronted by rust colored water most people immediately think their drinking water contains iron and purchase a test kit for iron in drinking water.

A good idea, yes, but some people do not know the differeence between free dissolved iron and total iron and inadvertently purchase a test kit that does NOT test for total iron.

So therefore, always make sure you test for total iron and not just free dissolved iron when worried about iron contamination in drinking water.