The Complete Guide to Winterizing Your Pool (Any Type)

If you skip winterizing, you’re gambling with thousands of dollars in equipment. 

A cracked pump housing, split pipes, and a heater that won’t fire up in May, these happen when water freezes in the wrong places. Everything else in this guide is downstream of that one fact.

The timing question gets people tripped up. You want to close when water temperatures stay consistently below 60°F, not when the calendar says October. 

Close too early in warm water and you’re handing algae a five-month buffet. Close too late and you’re chipping ice off your skimmer. Watch the water, not the leaves.

Start With the Chemistry

Balance the water a week before you close, not the day of. 

You’re aiming for a pH between 7.2 and 7.6, alkalinity of 80–120 ppm, and calcium hardness around 200–400 ppm. 

Shock the pool and let chlorine levels return to normal before adding winterizing chemicals, dumping algaecide into freshly shocked water just wastes the algaecide.

This single step matters more than any cover you buy.

Water that sits unbalanced for five months stains plaster, etches concrete, and corrodes metal fittings. The damage isn’t always visible in spring. Sometimes it shows up two seasons later when your heat exchanger fails, and the tech traces it back to low pH eating through copper.

Lower the Water 

The standard advice is to drop water 4–6 inches below the skimmer for mesh covers, or just below the tile line for solid covers. 

Vinyl liner pools are the exception worth knowing: they drain too much, and the liner shrinks, tears, or pulls away from the track. For above-ground pools with vinyl, leave the water high and rely on a skimmer cover or Gizzmo instead.

Concrete and fiberglass pools tolerate lower water levels, but there’s no reason to drain more than you have to. More water in the pool means more thermal mass, which means less violent freeze-thaw cycling at the waterline.

Blow Out the Lines

This is where most DIY closings go wrong. 

Every pipe between the pool and the equipment pad needs to be cleared of water, skimmer lines, return lines, main drain, dedicated suction lines for cleaners, and so on. A shop vac on blow mode handles small pools. Larger systems need a proper air compressor or a cyclone blower.

You’re done when you see bubbles coming from each return jet in the pool. Then you plug the returns with rubber expansion plugs and pour pool-grade antifreeze into the lines, never automotive antifreeze, which is toxic and won’t protect against the freeze ranges pool antifreeze handles.

The skimmer gets a Gizzmo (a hollow plastic tube that compresses if water freezes inside it) or a foam log. Something has to absorb the expansion when ice forms in there, or the skimmer housing cracks. Skimmer replacement on a gunite pool runs into real money.

The Equipment Pad

Drain the pump, the filter, the heater, the chlorinator, and any booster pumps. 

Remove drain plugs and store them in the pump basket so you can find them in April. Take pressure gauges off the filter, they freeze and crack reliably.

Cartridge filters need the cartridge pulled, hosed down, and stored somewhere dry. DE filters need a full breakdown and rinse. Sand filters are the easiest: drain, set the multiport to winterize, and walk away.

Salt cells come inside. So does anything else that would benefit from not sitting in freezing rain for five months.

Covers Are Not Equal

A solid cover with a cover pump on top will outperform a mesh cover for water clarity, but it demands attention all winter, you can’t let water and debris accumulate past the pump’s intake, or the whole thing sinks.

Mesh covers let dirty water through, which means a green pool in spring, but they’re nearly maintenance-free until opening day.

Safety covers, such as the anchored, strap-tensioned kind, are a different category. They cost more, but they last fifteen-plus years, and they actually hold the weight of a person or pet that wanders onto them. 

If you have kids, animals, or curious neighbors, this isn’t really optional.

Above-ground pools use a different system entirely: a winter cover held down by a cable and winch around the top rail, often with an air pillow underneath to absorb ice expansion and push debris to the edges.

What Changes by Pool Type

Inground gunite or plaster pools: most freeze-vulnerable, most equipment, most steps. Everything above applies.

Vinyl liner pools (inground or above-ground): protect the liner. Don’t overdrain. Watch for sharp objects under the cover.

Fiberglass pools: relatively forgiving, but the shell can flex if water levels drop too far and groundwater pressure pushes from outside. Keep water reasonably high.

Above-ground pools: the pump and filter often come off entirely and live in the garage. Pillow under the cover, water level just below the skimmer (or use a skimmer plate that lets you keep the water full).

Saltwater pools: same closing procedure as chlorine pools, but pull the salt cell, inspect it, acid-wash if needed, and store it indoors. The cell is the single most expensive component most people own, and freezing destroys it.

Mid-Winter Check-Ins

Don’t close the pool and forget it exists until March.

Check the water level after heavy rain or snowmelt. If it rises above the skimmer mouth, the water on top of your cover needs pumping off, or the cover needs draining. 

Walk around the pad once a month to confirm nothing has shifted, cracked, or sprung a leak from a freeze you didn’t know happened.

The pools that open clean in spring are the ones whose owners glanced at them in January.Keep winter prep simple with Aiper’s pool care tools, built to help you stay ahead of debris, waterline buildup, and seasonal maintenance before small issues turn expensive.