Wilmington water is soft to moderate at 39 to 62 mg/L, coastal salt aerosol settles as a hygroscopic film all year, and hurricanes leave debris film.
Wilmington's water is soft to moderately hard depending on which side of the blend serves you, so the tap is not what fails a job here; salt is, settling as a film that pulls moisture back all year. Hurricanes add debris film, so April, May, October and November are the safest months to wash. Ocean-facing homes run on short cleaning intervals, and a single-story exterior runs $280 to $480.
Forty-four ppm is soft, but the number that matters is which side of the blend an address sits on — 25 ppm on the Sweeney side, 65 on the Richardson side. Either way the mineral load is modest, and it is not what fails a Wilmington job. Salt is. A hygroscopic chloride film behaves in the opposite direction to scale, softening and spreading in humidity instead of hardening.
| Hardness | 39–62 mg/L as CaCO₃ Soft on average at 50 ppm in 2025, but published separately as 25 ppm on the Sweeney service area and 65 ppm on the Richardson service area. |
|---|---|
| pH | 7.5 (range 7.3–7.5) |
| Alkalinity | 80 mg/L as CaCO₃ (range 49–252) |
| Iron | 0.2 mg/L (range 0–0.2) |
| Manganese | 0.011 mg/L (range 0–0.011) |
| Sodium | 33 mg/L (range 13–33) |
| Chloride | 9 mg/L (range 8–10) |
| Total dissolved solids | 109.1 mg/L (range 66.9–323.3) |
| Disinfectant | ozone + chlorine |
| Source and treatment | Two plants feed one consolidated system: the 44 MGD Sweeney plant on the Cape Fear River and the 7 MGD Richardson plant on Castle Hayne and PeeDee aquifer groundwater, backed by emergency wells · Sweeney runs ultraviolet, ozonation and chlorine; Richardson is a low-pressure reverse-osmosis membrane plant, also chlorinated. No lime, soda-ash or ion-exchange softening step is described. · No softening step. |
Not in the report: corrosion index.
SOURCE · Cape Fear Public Utility Authority, 2025 Drinking Water Quality Report, CFPUA-Wilmington Water System PWS ID# 04-65-010 — 'Water Characteristics Contaminants', 'Other Miscellaneous Water Characteristics Contaminants', Disinfection Residuals Summary and the 'Water Disinfection and Health Effects' treatment description (cfpua.org/2025WaterQuality) · How we source these numbers
Distance from open water sets the interval far more than anything dissolved in the supply. Ocean and Intracoastal frontage runs on a short year-round cycle because salt never stops arriving; inland historic neighbourhoods run on a longer one driven by canopy and humidity. Hurricane season overrides both, and a single named storm can reset the whole city's schedule in a week.
NORTH CAROLINA SEASON BY SEASON →CFPUA's 2025 report publishes hardness at 50 ppm across a 39 to 62 range — and the reason for that spread is that it publishes two different figures by service area: 25 ppm on the Sweeney surface system and 65 on the Richardson nanofiltration system, consolidated into one distribution system in January 2023. The record carried 140, roughly three times the blend and two bands out. The address decides which water arrives. Above the tap it is salt aerosol, hurricane cycles and the pre-1900 riverfront core.
CFPUA publishes hardness twice, by service area, on its own brewery and restaurant page: 25 ppm in the Sweeney surface-water area and 65 ppm in the Richardson nanofiltration area. The consolidated system's 2025 report gives 50 ppm across a 39 to 62 range, which is simply those two waters blending. Which one reaches a given address depends on where in the system it sits, and no single figure describes the city.
The two plants are genuinely different machines. Sweeney treats Cape Fear River surface water through granular activated carbon, ozone and ultraviolet; Richardson is a groundwater nanofiltration and reverse-osmosis plant. In January 2023 CFPUA consolidated the two previously separate systems into one CFPUA-Wilmington distribution system fed by both, which is why the published range widened rather than narrowed.
The supporting chemistry on the Sweeney side is unusually low across the board — calcium 6.0, magnesium 1.9, sodium 14, sulfate 14, pH 7.3. Where the Richardson blend dominates, calcium runs 22 and hardness roughly two and a half times higher. The practical consequence is that the same crew can get different rinse results in two parts of the same city.
Coastal salt aerosol is the dominant residue in this market and it behaves nothing like mineral scale. Salt film is hygroscopic: it pulls moisture back out of humid air rather than drying hard, so glass can look worse on a damp morning after a clean than it did before. Ocean-facing and Intracoastal-facing elevations need a dedicated rinse protocol year-round, not a seasonal one.
Hurricane season restructures the working year. Named storms drive a debris film of salt, sand and organic matter that has to be flooded off before any contact cleaning, because wiping it drags grit across the glass. Demand arrives as a post-storm spike rather than a trend, and it runs heavy through September and October.
The Historic Downtown district is dense pre-1900 brick commercial and residential right on the Cape Fear River — one of the larger intact nineteenth-century districts in the South. Original sash, ornamental glazing and river-facing exposure combine there, so it carries both the highest care requirement and the heaviest salt and wind loading in the city.
Wilmington is at the centre of a long-running regional emerging-contaminant story on the Cape Fear River, and Sweeney's carbon, ozone and ultraviolet train exists substantially because of it. For this trade the relevance is indirect but real: treatment changes shift finished-water chemistry, and a city under active treatment upgrades is one where a figure from five years ago is not safe to reuse.
Subtropical humidity keeps dry-down slow and mildew pressure high on shaded elevations. Combined with salt, it means north and east faces in older neighbourhoods need materially more frequent attention than the same house's sunlit faces.
Proximity to salt water is the price structure in Wilmington: ocean-facing work runs on short intervals with dedicated rinse discipline, and it is priced on frequency rather than per-job rate. Storm response is the volatile second driver, arriving as an unplanned surge. Downtown's heritage frontage prices on care, and the gated communities along the Intracoastal add access administration that inland work does not carry.
Modern accessible glazing in Mayfaire or Landfall is within reach for a careful homeowner, and the soft supply helps. What does not transfer is the salt method — coastal film needs flooding and a surfactant rather than pressure, and the usual instinct to scrub drives sand across the glass and scratches it. Post-storm debris is the same trap in a worse form, and the downtown historic sash is conservation work rather than a harder version of a normal job.
OPEN COST ESTIMATOR →2025 annual mean at the Castle Hayne monitor, 6028 Holly Shelter RD, 17.8 km north of the city (EPA site 37-129-0002).
Largest air release: Corning Inc, 310 N College RD (nonmetallic mineral product), inside the city limits, 90,230 lb in 2024.
Wilmington's charter still treats wasted water as the council's business: where unnecessary waste is known or suspected, the city may enter the premises at reasonable hours, look into the cause, penalize anyone who blocks the inspection, and cut the supply until it happens. A hose left running between panes or a leaking tank fitting is the kind of thing that provision reaches.
Wilmington Charter §15.12: examining premises where water is being wasted · checked September 2026
Wilmington forbids causing or allowing any liquid, solid or other substance besides stormwater to be poured, pumped or discharged into a stormwater conveyance or state waters, or left on the ground where rain is likely to carry it there.
Wilmington City Code §12-22: illicit discharges prohibited · checked September 2026
Once a Wilmington landmark or historic district is designated, no exterior part of a building or structure, walls, fences, light fixtures, steps and paving included, may be erected, altered or restored without a certificate of appropriateness.
Wilmington Land Development Code §18-95: certificate of appropriateness required · checked September 2026
Outer Banks exposure is heavier than Charleston or Savannah due to the no-buffer barrier-island geography. Heavy pre-rinse and continuous-motion squeegee technique. IGU failure rate runs roughly double inland stock.
Tropical-storm and hurricane events drop salt-loaded rain, wind-driven leaves and small debris, and occasionally roof granules across glass in the eastern half of the state. Post-event cleaning wave runs for two to four weeks after a major landfall.
Wilmington runs on Cape Fear Public Utility Authority a mixed surface-and-groundwater blend at a published 39–62 mg/L (CaCO₃), averaging 50 — soft on average at 50 ppm in 2025, but published separately as 25 ppm on the Sweeney service area and 65 ppm on the Richardson service area.
Residential window cleaning in Wilmington typically runs $9–14 per pane or $280–480 for a standard single-story exterior. Proximity to salt water is the price structure in Wilmington: ocean-facing work runs on short intervals with dedicated rinse discipline, and it is priced on frequency rather than per-job rate.
Wilmington's drier, frost-free months are April and May and October and November, by NOAA's 1991–2020 normals for the Wilmington International Airport station, where August brings the most rain. The calendar on this page marks April (after the March 10 bloom), October (after smoke season) and November (before frost). Frost nights usually run from November 20 to March 19.
Yes, if the rinse is squeegeed off before it dries: Cape Fear Public Utility Authority publishes dissolved solids of 109.1 mg/L, between this site's two dissolved-solids flags. Iron, manganese, sodium and chloride all sit under this site's flags (highest: iron up to 0.2 mg/L). Treatment starts with sweeney runs ultraviolet, ozonation and chlorine.
In Wilmington the dominant residue patterns include coastal salt aerosol, hygroscopic and year-round and hurricane and tropical storm debris film. Distance from open water sets the interval far more than anything dissolved in the supply.
Modern accessible glazing in Mayfaire or Landfall is within reach for a careful homeowner, and the soft supply helps. What does not transfer is the salt method — coastal film needs flooding and a surfactant rather than pressure, and the usual instinct to scrub drives sand across the glass and scratches it.
Dense pre-1900 brick commercial and residential on the Cape Fear River. Original sash and ornamental glazing with direct river exposure — the highest care requirement and the heaviest wind and salt loading in the city. Forest Hills and Wrightsville Beach corridor have their own housing stock and glazing as well.
Just over the North Carolina line