Mount Pleasant runs deep Middendorf aquifer water through reverse osmosis, stripping out minerals wholesale, which changes what a tap rinse leaves behind.
Mount Pleasant runs deep aquifer water through reverse osmosis, stripping out minerals wholesale, and publishes no hardness figure, so a tap rinse leaves little behind; salt air near open water is what matters. Distance from open water sets how often a house needs cleaning, and the best months are February, April, May and October to December. Finish expectations run high across the waterfront market, and a single-story exterior runs $300 to $550.
No mineral value is claimed for Mount Pleasant, because the utility's own figure is not available and the obvious substitute — the Charleston Water System number that covers the towns next door — describes only one of two input streams and says nothing about what reverse osmosis and remineralisation produce downstream of it. The practical method is empirical: rinse one pane with plain tap water, let it dry untouched, and work from what it leaves. Reverse-osmosis blends can finish very low in mineral, but that is a reason to test rather than to assume.
Figures by source, as reported.
| Hardness | not published Mount Pleasant Waterworks publishes no hardness figure in its 2025 Annual Drinking Water Quality Report (issued 2026). |
|---|---|
| Sodium | 9.4–73 mg/L |
| Disinfectant | chloramine |
| Source and treatment | Purchased surface water with local wells, per the EPA SDWIS federal record · Diffused aeration for taste and odour, cartridge filtration, reverse osmosis for inorganics, rapid mix for byproduct control, and chlorination with chloramines as the residual · No softening step. |
Not in the report: pH, alkalinity, corrosion index, iron, manganese, chloride and total dissolved solids.
SOURCE · Mount Pleasant Waterworks 2025 Annual Drinking Water Quality Report (RO-treated groundwater and wholesale surface water tables), with the EPA SDWIS federal treatment record, PWS SC1010002 · How we source these numbers
Salt governs the calendar and proximity governs the salt. Harbour and creek frontage carries a film continuously, worst after a blow and never truly seasonal, because humidity keeps it active rather than letting it dry to a liftable dust. The inland subdivisions see a fraction of it. Pollen adds a heavy spring layer under the established planting in the older golf-course developments. The most durable wash of the year follows a settled offshore spell.
SOUTH CAROLINA SEASON BY SEASON →Mount Pleasant is the town in this batch where borrowing the neighbour's number would be a mistake, and the reason is worth understanding. Its utility treats deep Middendorf aquifer water — described by its own general manager as two thousand feet down and protected from surface contamination — by reverse osmosis, which strips dissolved minerals wholesale rather than filtering particles. It then blends in roughly six million gallons a day of conventionally treated surface water purchased from Charleston Water System. Finished hardness is therefore set by the blend ratio and the remineralisation step, not by the character of either source, and no figure is asserted here because the operator's annual report does not print one. What can be said is that marine exposure is severe on the harbour and creek frontage, and that several of the most period-looking districts are in fact recent construction with modern sealed glazing.
Mount Pleasant is the one town in this batch where the neighbouring figure cannot be borrowed, and the reason is the treatment rather than the source. Its utility runs reverse osmosis, which does not filter minerals out selectively — it strips dissolved solids wholesale through a membrane.
The primary source is deep groundwater. The utility's general manager has described the Middendorf aquifer as two thousand feet down and protected from surface water and man-made contaminants, and that is the water the reverse osmosis plant treats.
Alongside it the utility buys roughly six million gallons a day from Charleston Water System, which is conventionally treated surface water from the Edisto River and the Bushy Park Reservoir. Two entirely different products arrive in one distribution system.
No hardness figure is stated here because Mount Pleasant Waterworks' 2025 annual report prints none, and the arithmetic makes borrowing the Charleston number indefensible. Reverse osmosis removes the great majority of dissolved minerals and the finished water is remineralised afterwards, so what leaves the plant is a control-room outcome rather than a property of either source.
That gives this town two ways for a borrowed figure to mislead: the wrong source, or the right source measured before treatment. A number borrowed from the wholesale supplier describes only one of two input streams and none of the finished blend.
What can be said without a figure is that the marine exposure here is severe. The town sits between the harbour, the Wando and the Atlantic beaches, and the Old Village and Shem Creek frontage take airborne salt with nothing between them and open water.
There is also a trap in the building stock that catches visiting crews. Several of the most historic-looking districts are recent construction built in a traditional idiom, so a frame that reads as nineteenth-century may be a sealed modern unit — and the reverse is equally true a few streets away in the genuine Old Village.
Distance from open water sets frequency and frequency sets the annual spend, more than any measure of glass area does. Expectations are high across the waterfront market and the finish standard there is priced accordingly. Without a published water figure, any promise of a spot-free result in this town rests on an assumption about the blend rather than on a known supply, and a quote that leans on it is selling confidence rather than information.
Inland stock is comfortable homeowner work and the flood-first rule on salted glass is the thing worth learning before starting. Waterfront elevations in the Old Village and along the creek are better handed over on frequency grounds, since an honest interval there is short enough to be a routine rather than a project. The genuine Old Village houses carry original glazing that deserves conservation handling, which is precisely the distinction the surrounding traditional-style newer developments make easy to miss.
OPEN COST ESTIMATOR →2025 annual mean at the North Charleston Fire Station monitor, 2800 Carner Avenue (NCFS), 10.3 km north-west of the city (EPA site 45-019-0020).
In Mount Pleasant it is unlawful to take water from any public hydrant, or from private pipes on the hydrant service, without first contracting for that service with the Waterworks Commission, except in a life-threatening emergency. Hydrant meters are rented at rates the commission sets, and blocking or damaging a hydrant is also barred.
Mount Pleasant Code §51.055: fire hydrant rates and use · checked September 2026
Mount Pleasant makes it unlawful to drain or discharge petroleum products, alcohol, or chemicals or liquids of any kind, dangerous or not, onto or into any street, right-of-way, ditch or storm drainage system. That wording plainly covers a cleaning crew's chemical solution.
Mount Pleasant Code §51.186: discharge of grease, oil, gasoline · checked September 2026
In Mount Pleasant's Old Village Historic District, a certificate of appropriateness is needed before any exterior alteration, addition, new construction, site change, new fencing or hardscaping, or demolition, unless the Old Village Historic District Guidelines say otherwise. Even the town and utilities must go before the Historic District Preservation Commission.
Mount Pleasant Code §156.1261: applicability of certificates of appropriateness · checked September 2026
Not a contaminant but a conservation consideration. Original crown-and-cylinder glass survival rates 40-60% on better-preserved blocks. Conservative protocol — no scraping, water-fed pole or hand-detail only, test inconspicuous areas first.
No mineral value is claimed for Mount Pleasant, because the utility's own figure is not available and the obvious substitute — the Charleston Water System number that covers the towns next door — describes only one of two input streams and says nothing about what reverse osmosis and remineralisation produce downstream of it.
Residential window cleaning in Mount Pleasant typically runs $10–16 per pane or $300–550 for a standard single-story exterior. Distance from open water sets frequency and frequency sets the annual spend, more than any measure of glass area does.
Mount Pleasant's drier, frost-free months are February, April and May and October to December, by NOAA's 1991–2020 normals for the Charleston City station, where August brings the most rain. The calendar on this page marks April (after the February 28 bloom), October (after smoke season) and December (before frost). Frost nights usually run from December 30 to February 4.
Mount Pleasant Waterworks publishes neither hardness nor dissolved solids, so rinse one pane and let it dry in sun; a white ring means switch to pure water. Its sodium, up to 73 mg/L, leaves a salt film that pulls moisture back, so rinse it off rather than let it dry. It draws on purchased surface water with local wells.
In Mount Pleasant the dominant residue patterns include the operator's 2025 annual report prints no hardness figure for either source and reverse osmosis on deep middendorf aquifer water, stripping minerals wholesale rather than selectively. Salt governs the calendar and proximity governs the salt.
Inland stock is comfortable homeowner work and the flood-first rule on salted glass is the thing worth learning before starting. Waterfront elevations in the Old Village and along the creek are better handed over on frequency grounds, since an honest interval there is short enough to be a routine rather than a project.
The original eighteenth and nineteenth-century settlement on the harbour, with period houses, piazzas and original glazing, and open water directly in front of the most valuable elevations. Shem Creek and I'On have their own housing stock and glazing as well.
Just over the South Carolina line