As an essential part of our system’s maintenance program during the spring and fall of each year, Sudbury Water District opens hydrants in an effort to clear our water mains of sediment and mineral build up. This practice not only extends the life of our water mains but improves water quality.

To cleanse the system, we systematically open hydrants (unidirectional flushing/UFD) to increase flows, allowing us to “flush” minerals and deposits from the pipes. Though flushing won’t interrupt your water service, when crews are working in your area, you may notice a temporary drop in water pressure or discolored water. This is normal. After flushing hours (M-F 9 a.m. – 3 p.m.) or occasional evenings (after 8 p.m. only when noted) simply run a cold faucet briefly until the water runs clear, drawing out sediment from your service line.

ZONE II SPRING UNIDIRECTIONAL WATER MAIN FLUSHING is scheduled to begin APRIL 24th. Flushing will originate on Hudson Road at the intersection of Fairbanks Road heading northwest toward the Lakes Region and Town Line. Flushing will continue throughout the “remainder” of ZONE II.

(subject to change)

Kindle Note: A portion of ZONE II was flushed in 2018. If your street or neighborhood is located within ZONE II but has been omitted from the Spring 2019 UDF Street Index flushing was conducted and completed during the previous season (flushing begins where it left off.)


While flushing is underway homes and businesses in close proximity to the area being “flushed” may notice a temporary drop in pressure or experience discolored water which is normal during water main flushing and should subside overnight. When flushing mains; even if we are not directly flushing your street, connecting streets COULD experience some, all, or none of the same affects as that of the actual street being flushed. Water Conditions at homes and businesses within close proximity to the area being flushed will likely be influenced; avoid drawing in sediment into your own system by limiting intake during flushing hours. As the flushing route advances updates will be posted to our homepage under “recent new.” Major route changes will be electronically e-mailed to subscribers.

Routine Overnight Flushing is suspended until further notice.


Water main flushing is necessary to preserve water quality in the distribution system. Our goal is to flush all mains in our system each year. We cannot flush in the winter, because water that is flushed from hydrants could form ice and make driving and walking dangerous. We cannot flush in the midst of high demands periods, because that would be a burden on our system and leave us with no available flow for fire emergencies. That leaves us with a window of time in the spring and the fall, and occasional periods in the summer.

Every water system will gradually accumulate sediments in the water mains, and those sediments lead to reduced quality of water. When there’s a high localized demand and therefore higher than normal flows in the main, sediments are scoured into the flow of the water, creating discoloration. Furthermore, the sediments in the system, even when not stirred up, will react with chlorine, causing a reduction in chlorine at the points farthest from the dosing point. To counter that and provide sufficient disinfectant throughout the system, a higher dose of chlorine would have to be used, which can cause objectionable taste to the water for those who live closest to the dosing point and cause the formation of unwanted disinfection byproducts. Therefore, flushing is needed to protect water aesthetics and public health.

The Sudbury Water District is currently under water-use restrictions required by the Massachusetts Department of Environmental Protection (DEP) based on reduced water levels in the Concord River. DEP places those restrictions on usage as a measure to prevent further reduction in flow in the Concord River and other rivers and streams nearby, thereby protecting the environments of those water bodies. However, DEP allows us to flush our mains during this restriction period in recognition of the value that flushing provides.

Even though restrictions are currently in place, we still plan on flushing our water mains as much as possible. If we start to face high demand periods and our system’s pumps and piping cannot tolerate the additional demand from flushing, we will have no choice but to stop flushing altogether. Provided that is not the case, then we plan to continue to flush until the entire system has been addressed for the year. Our goal is to produce the highest quality water at the tap, and flushing is needed for us to meet that goal.


Avoid running your tap water or using a washing machine or dishwasher while flushing is conducted in your area. How do you know if flushing will effect your area? Sign up to receive notifications as the route advances through town or simply visit this website as often as you like.

If discolored water occurs due to area flushing, run a cold water faucet (after flushing hours) for a few minutes until the water runs clear or check for discolored water before using a washing machine or dishwasher.

If your white clothes or fabrics become stained due to discolored water, (only when water is running clear from your faucet) re-wash your laundry using detergent together with a Rust and Iron removing agent. Our business office maintains a free supply of Rust and Iron remover. Stop by anytime during regular hours to pick-up a few containers to keep on hand. These products also remove stains in toilets, sinks, tubs, tile and dishwashers.

Slight discoloration may sometimes linger for a few hours, it is not harmful to your health and only temporarily affects the appearance of the water it does not influence water quality.

If water pressure or volume seems low after flushing has been completed, check your faucet screens and home filters for trapped particles.

Flushing water mains may cause iron and manganese sediment to become more visible. Your water may at times appear yellow to dark brown in color (the actual minerals lifting in the water) and may also appear milky at times (air bubbles caused by the opening of the water mains). These non-health threatening minerals are known to cause staining. Be a wary consumer, to minimize the effect of these naturally occurring minerals, avoid using and/or purchasing products that contain chlorine (including automatic dishwashing detergents, laundry detergents, and any other household cleaning agents). Products free of chlorine are now available at most local grocery and department stores. Flushing also has an affect on water pressure. When in the area or your home, you may experience a reduction in the pressure coming into your home. That is because of the high pressure that is being drawn at the hydrants at the times of flushing.

When water has become noticeably discolored it is an indication that there has been a disturbance to the normal flow of water within the main. This disturbance may have been caused by the opening or closing of a water main valve, the opening of a hydrant for flushing or fire protection or a water main break. If the water inside the pipe changes either speed or direction or both, this change can cause the sediments inside the pipes to lift from the bottom and flow with the water resulting in brown water coming out of the tap. Running a cold faucet briefly will assist in clearing sediment from your service line.

Though the unidirectional flushing route is predetermined as flushing advances occasional adjustments may become necessary. Major route changes will be posted to our homepage and prompt an electronic notification to those who have signed up for notifications.

When flushing mains; even if we are not directly ON your street, the connecting streets COULD experience some, all, or none of the same affects as that of the actual street being flushed.