MVD has the following maintenance programs in place to maintain the water quality and supply: 

Water Flushing Program

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To maintain the water quality throughout the water distribution system, MVD performs a unidirectional flushing of the water mains each year as needed; typically in the spring and autumn.  The program involves opening hydrants to create increased water flow; this dislodges and cleans out naturally occurring sediment in the water mains.  

In order to keep customers aware of the progress*,  MVD provides notification of the streets scheduled for flushing on a weekly basis to Merrimack TV Online, as well as the two local newspapers. Additionally, the schedule is posted here: Flushing Schedule.  Flushing typically occurs between the hours of 8:00 AM to 3:00 PM.      

Please note: During the water flushing there can be fluctuations of pressure and/or brief interruptions of water service. Additionally, flushing may cause minor flooding of streets, and discolored water.

Discolored water is typically caused by sediment, such as iron. Although discolored water is not aesthetically pleasing, it is not unsafe* and can be easily resolved by flushing the water service line to the property. Flushing allows a larger than normal quantity of water to flow through the service line which helps clear out the sediment. You may notice the discoloration return after the water has sat in the lines for a period of time, such as overnight or during the day if it’s not being used – this is to be expected. When the water is not used for a longer period of time the sediment settles, when water is turned on it is agitated and the discoloration returns. If this happens you may repeat the flushing process. 

If your water is discolored, we recommend avoiding the use of hot water until the cold water is clear. If you have used hot water prior to/during flushing and are noticing discoloration in the hot water, the water heater may need to be flushed – refer to the manufacturer’s manual for instructions or contact a licensed plumber.

*Some people may be more vulnerable than the general population. These people should seek advice about from their health care providers.

 

Valve Exercising Program

MVD performs routine valve exercising on the water main valves to ensure the valves located throughout the water distribution system are in working order and able to be operated as necessary. Each valve is operated through a full cycle of shut-off and turn-on then returned to its normal position; this helps prevent buildup of sediment in the pipes that could render the valve inoperable or prevent a tight shutoff. 

Please note: During the valve exercising there can be fluctuations of pressure and/or brief interruptions of water service. Additionally, valve exercising may cause  discolored water.

Discolored water is typically caused by sediment, such as iron. Although discolored water is not aesthetically pleasing it is not unsafe** and can be easily resolved by flushing the water service line to the property. Flushing allows a larger than normal quantity of water to flow through the service line which helps clear out the sediment. You may notice the discoloration return after the water has sat in the lines for a period of time, such as overnight or during the day if it’s not being used – this is to be expected. When the water is not used for a longer period of time the sediment settles, when water is turned on it is agitated and the discoloration returns. If this happens you may repeat the flushing process. 

If your water is discolored, we recommend avoiding the use of hot water until the cold water is clear. If you have used hot water prior to/during flushing and are noticing discoloration in the hot water, the water heater may need to be flushed – refer to the manufacturer’s manual for instructions or contact a licensed plumber.

**Some people may be more vulnerable to contaminants in drinking water than the general population. These people should seek advice about from their health care providers.

Fire Hydrant Maintenance

MVD’s Hydrant Maintenance Program ensures that the hydrants are operable and available for use by the Merrimack Fire Department in an emergency situation.

Hydrants are flushed per MVD’s schedule and, typically, after any use by the fire department. During the flushing process MVD’s technicians perform an inspection of the hydrant and its parts to ensure the hydrant is operable and readily accessible. Inspection includes a visual examination of the hydrant; including checking valves, checking (and if necessary cleaning/lubricating) caps, inspecting for leaks, checking the flow of water, and assessing if there are any required repairs to the hydrant or area surrounding it.

During the winter months hydrants are cleared of snow and ice.

Hydrants are also painted as needed which is necessary to ensure the fire department can readily locate hydrants.

Backflow Prevention Program

Backflow devices are required by the New Hampshire Department of Environmental Services – Drinking Water & Groundwater Bureau (NHDES DWGB) as part of the Cross-Contamination Control Program.  In the event of a decrease or increase in water pressure, the backflow device protects any contaminated water from being siphoned back into the water system; protecting the water system from potential contamination.

MVD has licensed backflow inspectors who perform annual and semi-annual testing of the backflow devices. Annual tests are required for businesses considered “low” hazard (such as office buildings) and semi-annual tests are required for “high” hazard facilities (such as gas stations and medical facilities). Questions about this program? Please contact Jill Lavoie.