If tap water is used during flushing, it could come out discolored (commonly a rusty, orange, red, brown or black tint) and contain sediment.  If you encounter discolored water, shut the water off and wait several minutes.  After waiting, check the clarity by running cold water for a few minutes allowing new water to work its way into your building’s pipes.  Do not choose a tap that has a water filter connected to it, or the sediment may clog your filter.  Do not use a hot water tap because it could draw sediment into your hot water tank.  If the water is clear it is OK to use.  If not, wait 15-30 minutes and check again.  In some cases, there may be slight discoloration for several hours.

The water may also have a milky appearance.  This is almost always due to tiny air bubbles stirred up by the flushing and will eventually dissipate out and is not harmful.

There may be a temporary drop in water pressure during flushing.  If pressure or volume remain low after flushing, check your faucet screens for trapped particles.  Flush your hot water tanks, by running the hot water tap for a few minutes after the cold water clears.  For persistent pressure or volume problems, please contact your plumber.  Sometimes a pressure reducing valve in your plumbing is clogged or has failed, causing pressure loss.  Your plumber can advise you on the best course of action.

You may notice a more pronounced chlorine taste or odor in the water during flushing.  This is because free chlorine has a more noticeable chlorine taste and odor.  This will dissipate when water is left in an open container in the refrigerator.  Letting water in a glass sit for a moment will also take care of air bubbles that are stirred up during flushing and cause a milky appearance.

Water is generally safe to use during hydrant flushing, however it may look unpleasing, may taste metallic and/or may stain laundry.  The main causes of the discoloration of the water during hydrant flushing are iron (Fe) and manganese (Mn) deposits from inside the water mains.  The minerals occur naturally in ground water from our wells, and may also originate from corrosion of the iron pipes that were used to build a small portion of the water system.  Fe and Mn are essential nutrients for life.

Maximum Fe and Mn levels observed at our distribution system sampling stations are typically around 0.2 and 0.05 parts per million (ppm), respectively.  The State of NH has adopted a health-based Mn standard of 0.30 ppm.  The U.S. EPA and NH DES have established secondary limits in drinking water for Fe and Mn of 0.3 and 0.05 ppm, respectively.  For reference one ppm is equivalent to 1 inch in 16 miles or 1 minute in 2 years.  The secondary limits are based on the potential for aesthetic (taste/odor/stain) issues.  According to the treatment experts, in most NH cases staining problems do not become objectionable until the actual concentrations of Fe/Mn are at least double the secondary standards.

To minimize the potential for laundry staining, the Precinct adds a food grade polyphosphate to the water to prevent the formation of the rusty forms of Fe/Mn.  The polyphosphate "coats" and "ties up" (or “sequesters”) the dissolved Fe/Mn preventing a reaction with oxygen and subsequent precipitation.

Yes, the Precinct will occasionally flush hydrants throughout the year.  Usually this is associated with the installation or repair of water mains, but may also be associated with other activities such as troubleshooting various distribution system issues; addressing water quality complaints; maintaining or testing our wells and source meters; hydrant flow testing; and periodic training events.  These types of activities are very localized to specific hydrants and typically you won’t even notice it occurring.

It’s safer for staff to work on the streets in daylight.  Also, daylight provides better visibility to see when all the sediment has been flushed out and the water is running clear.

No, this is a normal and necessary part of maintaining a safe and reliable drinking water supply.  Water that is discharged into the environment will replenish groundwater systems and streams.