Fall Pool Closing: How to Winterize Your Pool and Spa Properly

When to close your pool

Close your pool when daily water temperatures consistently drop below 65°F (18°C) and nighttime temperatures approach freezing. Closing too early while temperatures are still warm promotes algae growth under the cover; closing too late risks freeze damage to plumbing and equipment. In most northern climates, the ideal window is mid-October through early November. The total process takes 3–5 hours for an average residential pool.

Water chemistry before closing

• Balance the water first — adjust pH to 7.2–7.6, total alkalinity to 80–120 ppm, and calcium hardness to 200–400 ppm; properly balanced closing water prevents staining, scaling, and surface etching over winter
• Shock the pool — add a triple dose of chlorine shock (3 lbs per 10,000 gallons) 3–5 days before closing; this provides a high residual that will last through the first weeks under the cover
• Add winterizing chemicals — use a winterizing kit ($30–$60) that includes an algaecide (copper-free to prevent staining), a phosphate remover, and a metal sequestrant; add these 24 hours after shocking, once chlorine drops below 5 ppm
• Lower the water level — for mesh covers, lower water 12–18 inches below the tile line; for solid covers with a cover pump, lower 3–6 inches below skimmer openings; the exact level depends on your plumbing configuration

Plumbing and equipment winterization

• Blow out the lines — use a shop vac or air compressor (set below 25 PSI to avoid damaging PVC) to blow water out of every return line, skimmer line, and main drain line; this is the single most critical step — water left in pipes will freeze, expand, and crack underground plumbing ($500–$2,000 per line to repair)
• Install winterizing plugs — thread threaded plugs or rubber expansion plugs into each return fitting and skimmer; use Teflon tape on threaded plugs for a watertight seal
• Drain equipment — drain the pump housing, filter tank, heater, chlorinator, and any auxiliary equipment; remove the pump drain plug and store it in the pump basket so you can find it in spring; open air bleeders on filter tanks
• Add antifreeze to skimmers — pour 1–2 gallons of non-toxic pool antifreeze (propylene glycol) into each skimmer after plugging — this protects the skimmer body from cracking if water seeps in
• Disconnect and store — remove the pump motor if stored outdoors in harsh climates, or install a pump cover; bring chemical feeders, automation controllers, and removable ladders/rails indoors

Cover installation

• Mesh vs. solid covers — mesh covers allow snowmelt to drain through (no cover pump needed) but pass fine debris; solid covers keep debris out but require a cover pump to prevent water accumulation ($40–$100 for an automatic cover pump)
• Safety cover anchoring — if you have a safety cover, check all springs, straps, and brass anchors before installation; replace any stretched springs or frayed straps; anchors should be flush with the deck when not in use
• Water bags and clips — for standard winter covers, fill water bags only 2/3 full (to allow expansion when they freeze) and place them around the perimeter; never use bricks or cinder blocks, which can damage the pool edge and fall into the water
• Leaf net option — if your pool is surrounded by deciduous trees, install a leaf net over the main cover during fall; remove it after leaves finish dropping to reduce cleaning effort

When to call a pool professional

Homeowners who are comfortable with pool chemistry and basic plumbing can close their own pools with $50–$100 in winterizing supplies. However, call a licensed pool technician for: blowing out lines if you don't own a shop vac with sufficient CFM (improper blowout is the #1 cause of winter plumbing damage), pools with complex plumbing (multiple suction lines, water features, spa plumbing), above-ground pools in freeze zones that require specific antifreeze procedures, or your first time closing — watch a professional do it once ($250–$450 for a full service closing) so you learn the specifics of your system. Many pool companies offer combined opening and closing packages ($400–$700) that are more economical than individual services.