Tacoma Water calls its supply soft, one to two grains per gallon or about 17 to 34 mg/L, and switches between river and well sources with the season.
Tacoma Water calls its supply soft without hedging, so an ordinary tap rinse dries clean anywhere in the city; the one risk is over-soaping, which soft water makes easy. Bay air drives how often glass needs attention, and May to September is the time to wash. In the bluff neighborhoods setup takes longer than the wash, so grade sets the day rate; a single-story exterior runs $300 to $510.
One to two grains per gallon is soft by any reckoning, and the operator says as much without hedging. On glass that means an untreated tap rinse will dry clean anywhere in the city, and the only mineral-related risk is over-soaping, which soft water makes easy to do. If a Tacoma pane is drying badly the cause is technique, timing or what the air deposited on it — not the supply, and chasing the water is chasing the wrong variable.
Figures by source, as reported.
| Hardness | 17–34 mg/L as CaCO₃ Soft, one to two grains per gallon, in the utility's own words, as published by Tacoma Water (Tacoma Public Utilities). |
|---|---|
| Disinfectant | free chlorine |
| Source and treatment | Green River surface water with wells used seasonally, which the utility says changes taste and odour through the year · Pre-ozonation for taste and odour, coagulation, flocculation, sedimentation and rapid sand filtration, diffused and packed-tower aeration, pre and post chlorination, fluoridation and post pH adjustment · No softening step. |
Not in the report: pH, alkalinity, corrosion index, iron, manganese, sodium, chloride and total dissolved solids.
SOURCE · Tacoma Water 2025 Water Quality Report · How we source these numbers
Distance from the bay sets one clock and shade sets the other. Shoreline glass carries salt film continuously, worst after a blow and never fully seasonal, because humidity keeps it active. Inland, biological growth builds through the wet months from autumn to late spring and retreats only in the dry part of summer. Leaf and sap peak in autumn in the canopied districts. The most durable wash of the year is one taken in a settled July or August stretch.
WASHINGTON SEASON BY SEASON →Tacoma Public Utilities states its own answer in ordinary words: the water is soft, one to two grains per gallon, and it takes less soap than hard-water areas. At roughly 17 to 34 mg/L the rinse water is never the limiting factor on a Tacoma window. The same utility adds a detail worth more than the number — taste and odour shift through the year because the source changes between river and well, and because algae grow seasonally in the Green River. A supply that alternates like that has a character that moves even when its hardness band does not. The real adversaries here are two, and they divide geographically. On the Commencement Bay shoreline it is airborne salt, which stays damp and keeps collecting whatever else is in the air. Inland under the canopy it is biological growth on shaded elevations, which has to be lifted rather than dissolved. The bluff districts add grade to both.
Tacoma Public Utilities answers the hardness question directly and in plain language, describing the water it provides as soft at one to two grains per gallon, and noting that washing clothes there takes less soap than in hard-water areas. Between about 17 and 34 mg/L, that is genuinely soft water.
The same utility page flags something more useful still for anyone judging glass: taste and odour vary through the year because the source changes, specifically whether the water came from a river or a well, and because of seasonal algae in the Green River.
A supply that alternates between surface water and groundwater through the year is a supply whose character moves, even when the hardness band does not. What dries on a pane in late summer is not chemically identical to what dries on it in winter, and that is the operator's own account rather than an inference.
With the mineral question settled at one to two grains, tap water is an entirely adequate final rinse on every job in this city. The equipment argument for deionised water does not apply here, and a quote that includes it is selling a solution to a problem Tacoma does not have.
What does matter is the marine edge. Tacoma wraps around Commencement Bay, and the shoreline frontage takes salt spray across open water with nothing in the way. Salt is hygroscopic, so it stays damp on the glass and keeps attracting whatever else is airborne.
Inland from the water the problem inverts and becomes biological. Under the mature canopy of the northern residential districts, shaded elevations hold moss, algae and lichen through a long wet season, and that growth has to be lifted mechanically rather than dissolved.
The bluff neighbourhoods add grade to both problems. A house on the Stadium District slope presents a working face taller than its storey count suggests, and the older stock there carries original wood sash that punishes a hurried blade around putty and paint.
Proximity to the bay drives frequency, and frequency drives the annual figure far more than pane count does. Grade sets the day rate in the bluff neighbourhoods, where setup takes longer than the washing. Route density splits the city sharply: the compact commercial strips are efficient to work, while the large-lot northern districts spread a crew thin. Because the water is soft, no part of a Tacoma quote should be carrying the cost of treated rinse water.
Flat inland properties are reasonable homeowner work provided moss is lifted patiently rather than scraped, particularly around old wood frames where the putty gives way before the growth does. Waterfront elevations are better hired out on interval alone: honest frequency there is short enough that it becomes a standing arrangement rather than a project. Bluff-side houses are an access decision before they are a technique decision, because the downhill face is taller than it looks from the street.
OPEN COST ESTIMATOR →2025 annual mean at the Tacoma-S 36th St monitor, 1802 S 36th St, 2.9 km south of the city (EPA site 53-053-0024).
Largest air release: US OIL & Refining Co, 3001 Marshall AVE (petroleum), inside the city limits, 89,242 lb in 2024.
Tacoma Water runs its 10,500 hydrants under Tacoma Municipal Code 12.10.305: before anyone draws from one for a non-fire purpose they must finish the utility's free hydrant training and carry its certification card, have backflow protection approved, and hold an approved hydrant use permit. Unauthorized or improper hydrant use can cost the permit and a $1,000 penalty for each occurrence.
Tacoma Public Utilities: Hydrant Use Permit Policy (TMC 12.10.305) · checked September 2026
Tacoma bans discharging anything not allowed or conditionally allowed into its storm system. Routine exterior building wash-down without detergents is conditionally allowed, but commercial, industrial and multistory residential buildings built or remodeled between 1950 and 1980 must first be assessed for PCB-containing materials, and those with such materials may not send washdown to the storm system.
Tacoma Municipal Code §12.08D.110: allowable, conditional, and prohibited discharges · checked September 2026
Alterations to properties on the Tacoma Register of Historic Places go through a certificate of approval, with the Landmarks Preservation Commission judging their appropriateness against the code's review standards.
Tacoma Municipal Code §13.07.095: certificates of approval, standards for review · checked September 2026
The defining substrate problem of western Washington. Moss and algae establish on north-facing glazing, on stone and brick masonry trim, on aluminum and vinyl frames, and on cedar-shingle exterior cladding within a few years of installation. The growth feeds on the maritime humidity and the deciduous-conifer organic load. Removal requires a sodium-percarbonate or quaternary-ammonium pre-treatment, careful rinsing, and an awareness that aggressive scraping will damage anodized aluminum and vinyl. This is the technical specialty of the Washington trade.
Tacoma runs on Tacoma Water (Tacoma Public Utilities) lake or reservoir surface water at a published 17–34 mg/L (CaCO₃) — soft, one to two grains per gallon, in the utility's own words. One to two grains per gallon is soft by any reckoning, and the operator says as much without hedging.
Residential window cleaning in Tacoma typically runs $10–15 per pane or $300–510 for a standard single-story exterior. Proximity to the bay drives frequency, and frequency drives the annual figure far more than pane count does.
Tacoma's drier, frost-free months are May to September, by NOAA's 1991–2020 normals for the Tacoma Narrows Airport station, where January brings the most rain. The calendar on this page marks May (after the April 14 bloom and after smoke season) and June (before frost). Frost nights usually run from November 21 to March 11.
Usually yes: Tacoma Water (Tacoma Public Utilities) publishes hardness of 17–34 mg/L, low enough that tap-rinsed glass tends to dry clean. It draws on Green River surface water with wells used seasonally, which the utility says changes taste and odour through the year.
In Tacoma the dominant residue patterns include soft supply at one to two grains per gallon in the utility's own words, about 17–34 mg/l and seasonal source switching between river and well water, flagged by the operator itself. Distance from the bay sets one clock and shade sets the other.
Flat inland properties are reasonable homeowner work provided moss is lifted patiently rather than scraped, particularly around old wood frames where the putty gives way before the growth does. Waterfront elevations are better hired out on interval alone: honest frequency there is short enough that it becomes a standing arrangement rather than a project.
Early twentieth-century commercial blocks alongside civic and museum glazing, with the Thea Foss Waterway immediately east. Marine air reaches this frontage directly and the institutional buildings run on fixed contracts. Stadium District and North End have their own housing stock and glazing as well.
Just over the Washington line