Maine runs as five working zones. Portland and the southern coastal corridor on Portland Water District Sebago Lake-source surface supply (among the cleaner municipal supplies in the country). Bangor and central Maine on Bangor Water District surface-and-aquifer-supplemented supply. The Down East coastal corridor on mixed municipal supplies with substantial coastal salt-aerosol overlay. Northern Maine and the Aroostook County corridor on mixed municipal and aquifer supplies. The lakes-and-mountains corridor on mixed mountain-source and aquifer-supplemented supplies. Rural Maine well-water through the inland backcountry on local aquifer and well-water systems.
HOW IT BREAKS DOWNsoft (Auburn, Lewiston, Portland, South Portland, Bangor)
Portland Water District Sebago Lake-source supply is among the cleaner municipal supplies in the country — Sebago Lake is one of the few major water sources in the U.S. that does not require filtration treatment. Coastal salt-aerosol overlay is the heaviest on the entire Atlantic coast — operationally distinctive working factor. Pre-1800 heritage residential in Portland Old Port and Kennebunkport. Lobster-boat commercial residue exposure on working-waterfront properties. Substantial seasonal-tourism commercial concentration through Bar Harbor, Boothbay Harbor, Camden, Ogunquit, Kennebunkport. Longest winter exterior shutdown in the lower 48 (November through March). Heavy ski-corridor seasonal commercial through Sugarloaf, Sunday River, Saddleback, Mt Abram. L.L. Bean institutional commercial concentration in Freeport. Foliage-season commercial concentration October. Cottonwood and ash-pollen wave late onset May-June.
A blended system means hardness moves with the blend. Two addresses on the same utility can read differently, and the same address can read differently across a year, depending on which source is carrying the load that season.
Maine sits in one band statewide, so the answer is the same everywhere in it.
Tap water is clean enough to be the last thing that touches the glass. Wash with it, rinse with it, squeegee it off, and nothing measurable is left behind when it dries. No distilled rinse, no deionized final pass, no spot-free rinse aid — the mineral load is too low to precipitate anything you would see. The failure mode at this end of the scale is not water chemistry, it is technique: streaks here come from a worn rubber, a dirty edge, or a pass that dried before it was pulled.
Hardest first — the order that matters, because the hard end is where the method has to change. Each figure is the named utility's own published number; cities whose utility publishes none are listed after them, without a band. Within Maine the spread runs from Bangor at 5.3 mg/L to Lewiston at 17 mg/L — a difference big enough that the same bottle of cleaner behaves differently in each.
Where Maine's city pages sit in the national city rankings: hardness rank out of 185 cities whose utility publishes a figure, dissolved-solids rank out of 100, the disinfectant each utility reports, and the months each city's cleaning calendar marks for a wash. Rank 1 is the hardest or most mineral-heavy. 5 of these 5 cities use chloramine.
| CITY | HARDNESS RANK | TDS RANK | DISINFECTANT | WASH IN |
|---|---|---|---|---|
| Auburn | 176 / 18517 mg/L | not ranked | chloramine | Jun |
| Lewiston | 176 / 18517 mg/L | not ranked | chloramine | Jun |
| Portland | 182 / 1857.2 mg/L | not ranked | chloramine | Jul |
| South Portland | 182 / 1857.2 mg/L | not ranked | chloramine | Jul |
| Bangor | 185 / 1855.3 mg/L | not ranked | ozone + chloramine | Jul |
This page is about Maine's water and nothing else. For how cleaning actually works in Maine across the year — climate, seasonal timing, the local contaminants, the housing stock — see the Maine cleaning guide.
For a figure at your own address rather than your city, the Hard Water Scorer takes a ZIP code. If you run a pure-water system, the TDS diagnostic reads the other end of the same problem.
Each covered city utility's own published figure, taken from its most recent annual water quality report (Consumer Confidence Report) or its water-quality page, read in 2026. A city figure is the one its utility publishes for the service area, as a single number or the range it reports; it is not a reading from any one tap. A state range runs from the lowest to the highest figure published by the utilities we cover in that state, so it brackets those cities rather than describing an average resident. A state where no covered utility publishes a figure shows a planning estimate, labelled as one.
Private wells are outside all of it. A well is whatever the rock under it says, and the only number that describes one is a test of that tap. Have a reading that disagrees with this table? Send it to us — a number that contradicts the table is worth more than one that confirms it.