Wilmington, Delaware Water Outage Today

Wilmington water system at a glance

Federal records name Wilmington Water Department as the public water system for Wilmington, with about 107,976 people on its mains. Customers know it as City of Wilmington Water Division; the name on your bill is the one to call.

Where Wilmington's tap water comes from

Tap water in Wilmington starts as surface water. Wilmington Water Department takes it from the Brandywine River, the Hoopes Reservoir, and the Cool Springs Reservoir and runs it through treatment before it reaches the mains. Treatment points named in EPA's facility list include Brandywine Plant and Porter Plant. After treatment the water is held in 9 storage tanks and reservoirs, which is the buffer that keeps taps running for a few hours after a pump or main fails.

Why this matters when the water stops. Surface water needs a treatment plant running around the clock, so a plant shutdown, a raw-water pump failure or a long power cut at the plant can lower pressure across the whole service area, not just on one street. Boil water notices are more likely to be citywide after that kind of failure than after a single main break. EPA lists 2 emergency connections to neighboring systems, which can be opened to move water across a boundary during a failure.

Why the water goes out in Wilmington

Water outages are local, so the likely cause depends on weather, pipe age and the grid. For Wilmington, these stand out.

• Freezing weather. Wilmington sees about 86 days a year with a low at or below 32°F, and 14 days at or below 20°F. The coldest morning in the 2015 through 2025 record came on March 6, 2015. The longest stretch with highs that never rose above freezing ran 13 days, ending January 8, 2018. Frozen service lines and meters cause single-address outages, while ground frost and thaw cycles crack older mains and produce the street-wide breaks.
• Flooding and heavy rain. NOAA logged 114 flood, flash flood and heavy rain reports in New Castle County from 2015 through 2026, and 8 days a year bring an inch of rain or more. High water can wash out the ground under buried pipe, flood pump stations and push treatment plants past their limits, which is why boil notices so often follow a flood.
• Older neighborhoods and pipe. 72.1% of occupied homes in Wilmington were built before 1970, against 35.5% nationally. Streets of that age tend to sit on cast iron and early steel mains that are near or past their design life, which is where most breaks start.
• Long dry spells. The longest stretch without measurable rain since 2015 lasted 45 days, ending October 21, 2019. Dry soil shrinks and shifts around buried pipe, and breaks often cluster when the rain returns and the ground swells again.
• Storm-driven power loss. Thunderstorm wind, hail and tornado reports in New Castle County number 259 since 2015. Pump stations and treatment plants that depend on Delmarva Power run on the electric grid, so a storm that downs power lines can lower water pressure even when no pipe is damaged.
• Digging and utility work. Street projects, fiber installation and excavation near buried pipe regularly cut mains in Wilmington with no warning, usually on a day with perfectly ordinary weather.

How weather strains the Wilmington water system

Main break season in Wilmington runs from late fall into early spring, with the coldest stretch around December through February.

The figures are reanalysis estimates for the center of Wilmington, not readings from a single weather station, so treat them as a guide to how often each kind of weather occurs rather than as official records.

Boil water advisories and the federal violation record for Wilmington

EPA lists 1 health-based violation for Wilmington Water Department since 2015. It also lists 4 monitoring or reporting entries that are about paperwork rather than water quality, such as a missed sample or a late report.

Most recent health-based entries:

• October 2017: A treatment technique violation It is marked resolved.

A boil water notice in Wilmington is a separate thing from a violation. City of Wilmington Water Division issues one when pressure falls low enough for contamination to enter the pipes, after a main break is repaired, or when a routine test comes back positive. The Delaware Office of Drinking Water oversees the process, and the notice stays until clean samples come back, usually a day or two after pressure returns.

Lead service lines and old plumbing in Wilmington

The most recent 90th-percentile lead result filed for Wilmington Water Department is 0 ppb (2023). The federal action level is 15 ppb, so that result is comfortably below it.

The age of the housing matters more than the utility's test average: 72.1% of occupied homes in Wilmington predate 1970 and 1986 was the year lead pipe and solder were banned. Flush the cold tap after an outage and ask City of Wilmington Water Division whether your service line is on its lead inventory.

How long a water outage lasts in Wilmington

Most repairs of an ordinary main break in Wilmington take half a day once the crew is on site. Bigger mains, deep bury and busy roads stretch that to a day or more.

Ask City of Wilmington Water Division for a restoration estimate when you report the outage; for large breaks it is normally posted and updated as the repair progresses.

Preparing for a long water outage in Wilmington

Census figures put the typical Wilmington household at about 2.3 people. At one gallon per person per day that is 7 gallons for three days or 32 gallons for a two-week supply.

• 19.6% of homes are in buildings with 20 or more units. Upper floors lose pressure first, and rooftop tanks and booster pumps depend on building power.
• 52% of households rent. Tell your landlord or property manager about a leak or outage right away, since the shutoff valve may be theirs.
• Your water heater tank holds 30 to 50 gallons of clean water. Turn off the power or gas to it first, then drain from the valve at the bottom.
• Fill the bathtub and a few large pots as soon as you hear a break is likely; that water is for flushing and washing, not drinking.

Water systems near Wilmington, side by side

Water outage pages for nearby cities

Newark, DE · Philadelphia, PA · Lancaster, PA · Reading, PA