Pool closing · South Carolina
When to Close Your Pool in Mount Pleasant, SC: Deadline, Window & Checklist
Last updated: July 15, 2026 · Model window year: 2026 · dates · checklist · FAQ
In Mount Pleasant, the closing window runs from November 5 to November 15. Let the water cool out of the algae-growth range before covering — close too warm and you lift the cover onto a green surprise in spring — but finish ahead of the first freeze, which normals place around November 30. The live estimate below shows where Mount Pleasant's water sits today.
Mount Pleasant closing dates at a glance
| Closing window | November 5 – November 15 |
|---|---|
| Close by (deadline) | November 15 |
| First freeze, 50% probability | November 30 |
| Open by (recommended) | March 23 |
| Opening window | March 16 – April 6 |
| 61°F crossing (7-day mean) | April 6 |
| Swim-season length (80°F+ days) | 159 days |
| NOAA normals station | Sullivans Island · 6.7 mi · 5 ft |
A classic four-season pool calendar: open early into cold water, close late into cold water, and Mount Pleasant's 159 days of prime swimming sit safely in between.
Put dates aside and follow the water: the Mount Pleasant curve says roughly 62°F by mid-April, 78°F by mid-June, 82°F in mid-August, then back down through 70°F in mid-October. The summer ceiling sits near 82°F, and every window above is just a line drawn on this curve.
The 12-step Mount Pleasant winterizing checklist
Sequenced against Mount Pleasant's November 5–November 15 window: chemistry while the pump still runs, blowouts before the equipment drains, cover last. Labels dictate every dose.
-
Balance the water a few days ahead
Give the chemistry a head start — balance to label ranges several days out, while circulation can still mix corrections evenly. Closing-day dosing never distributes as well.
-
Deep-clean the pool
Make the last cleaning the best one of the year: full skim, full brush, careful vacuum. Debris left behind steeps all winter and greets you as April's water problem.
-
Service the filter one last time
One final filter service per the manual — cartridges rinsed and stored dry indoors, sand or DE backwashed. Winter turns trapped gunk into concrete.
-
Apply winter chemicals per label
Dose the winter kit while the pump still runs — every product exactly per its label for your volume — so the chemistry is fully mixed before the system goes quiet.
-
Lower the water level
Check the cover manufacturer's spec before touching the hose: solid covers typically want water below the skimmer mouth, mesh often barely lower than normal. Full draining is off the table entirely.
-
Blow out the lines and plug returns
Work line by line: push air until the return spits dry mist, plug it against the flowing air, move on. Skimmer, returns, cleaner line, in whatever order your plumbing prefers — dry pipes are the entire point of closing.
-
Protect the skimmer
Install a skimmer guard bottle (or a plug rated for your skimmer) so ice that forms there crushes the sacrificial piece instead of cracking the skimmer body.
-
Add pool antifreeze where blowouts fall short
Any line you can't prove is dry gets pool-grade antifreeze at the label's rate per foot. Automotive antifreeze is toxic in this context — pool-rated only, always.
-
Drain the equipment
Every vessel on the pad — pump, filter, heater, chlorinator — gets its drain plugs pulled. Drop all the plugs in the pump basket; that's the one place everyone looks first in spring.
-
Set the air pillow and cover
Inflate the pillow to about two-thirds, center it, then bring the cover over and secure it per its design. Under ice, that soft dome is the difference between inward compression and outward wall pressure.
-
Winterize the water features
Waterfalls, slides, and spillover spas hold water in places gravity won't clear — blow those lines separately and plug them, or they'll be the one crack you find in spring.
-
Stage the cover pump
Solid covers need drainage all winter: set a cover pump or siphon before the first storm, not after. Standing water strains seams and invites a mid-winter emergency.
What to buy before the rush
Every item below sells out somewhere in South Carolina every November. Stocking the short list before the rush costs nothing extra and saves the mid-project store run — the chemicals guide explains what each category actually does.
-
Cover pump
Standing water is a cover killer; this is the counter.
-
Expansion plugs + skimmer guard
The blowout's finishing move — one per return, one for the skimmer.
-
Pool antifreeze
Pool-rated glycol for the lines air couldn't clear.
-
Winter closing kit
Season-length winter chemicals in one label-dosed box.
-
Air pillow
Centers under the cover so ice pushes inward, not outward.
-
Winter cover
The one purchase every other closing step depends on.
How Mount Pleasant compares locally
Statewide context: across the 12 South Carolina cities we model, Mount Pleasant's November 15 deadline sits in the earlier half. Nearby, Charleston (9 mi) closes around November 21 and North Charleston (15 mi) around November 15 — treat gaps under a week as microclimate noise, not strategy. Spring planning restarts at the opening guide; the Mount Pleasant pool season page keeps the whole year in one view.
Local means local: Mount Pleasant's dates come from Sullivans Island, the nearest station with complete daily temperature normals — 6.7 miles south, about 5 feet up. Between that station and a Charleston County backyard there's always a degree or two of microclimate; the windows are built wide enough to carry it.
Field notes for Mount Pleasant owners
Cold water is the whole point
A pool closed at 55°F barely changes all winter: algae are dormant, chemicals hold, and spring opens with a light dusting instead of a bloom. A pool closed at 72°F runs its own quiet ecosystem under the cover for a month. The date matters less than the water temperature it represents.
The warm spell after you closed
A 78°F week in October doesn't mean reopening. Water under an opaque cover warms far less than air suggests, and a closed, balanced pool tolerates a warm stretch fine. Check the cover pump has somewhere to send rain, enjoy the weather, and leave the plumbing sealed.
What comes indoors
Cartridges, the cover pump when idle, chemical containers, and anything with a small motor overwinter better in the garage. Cold cycling is hard on plastics and seals; shelf space is cheaper than replacements. Label a single bin now and spring assembly becomes a scavenger hunt with a map.
Mount Pleasant pool closing FAQ
What temperature should water be to close a pool?
Close once water holds below about 65°F — the point where algae go mostly dormant — and before hard freezes. In Mount Pleasant, the 7-day mean drops through the threshold around November 5, so the window between then and November 15 is the sweet spot for a clean, stable close.
Can you close a pool too early?
Absolutely. A pool closed warm is an algae incubator: no circulation, fading sanitizer, and weeks of growth-friendly temperatures. Mount Pleasant's water doesn't settle below the risk zone until around November 5 — closing much before that trades a few weekends of maintenance for a rough spring.
Do I need antifreeze in pool lines?
Only for lines you can't verify dry — a proper blowout makes antifreeze unnecessary. Where doubt remains, use pool-grade product at its label rate, never automotive. No freeze-probability normal is published near Mount Pleasant, so let the live forecast, not a calendar, tell you when freeze protection starts mattering.
How far should I drain my pool for winter?
Follow the cover's instructions first: solid covers usually want water a few inches below the skimmer; some mesh setups run higher with the skimmer sealed. The hard rule is never empty — hydrostatic pressure can lift or crack an empty pool, a far worse outcome than any freeze.
What happens if you don't winterize a pool?
The freeze finds every shortcut. Ice in an unprotected pump or heater cracks castings from the inside; ice in underground lines splits fittings you can't see until spring. Mount Pleasant reaches freeze territory around November 30 — the checklist above is cheaper than any one of those repairs.
When is the last safe date to close in Mount Pleasant?
The model draws the line at November 15 for Mount Pleasant. It isn't arbitrary: the cool-down plus ten days (the freeze normal, November 30, leaves room to spare), and the whole closing sequence needs a working weekend of margin. The one exception that overrides any date — a hard freeze inside the 10-day forecast, which the widget above flags as urgent.
Email me when Mount Pleasant hits the closing window
Data: NOAA 1991–2020 climate normals via Sullivans Island (6.7 mi); live outlook by Open-Meteo. Full attribution on the sources page. Model assumptions and error bars on methodology.