Seasonal Guide
Close your pool the right way and spring opening is easy. Skip steps now and you could face a green mess, damaged equipment, or expensive plumbing repairs. Follow this checklist in order.
Close your pool when the water temperature consistently stays below 65°F (18°C). Algae grows very slowly below this temperature, so your winterizing chemicals will last through the off-season. If you close too early while the water is still warm, algae can bloom under the cover.
Get your water balanced before adding winterizing chemicals. Target ranges for closing:
pH: 7.2-7.6
Total Alkalinity: 80-120 ppm
Calcium Hardness: 200-400 ppm
Balanced water protects your surfaces and equipment all winter. Water that is too acidic corrodes metal fittings and etches plaster. Water that is too alkaline deposits scale.
Add a heavy dose of chlorine to kill any bacteria, algae, or organic contamination before the pool sits dormant. Use calcium hypochlorite or liquid chlorine. Target 10-12 ppm free chlorine. Run the pump for 24 hours to circulate.
Algaecide: A quality winter algaecide helps prevent algae growth over the off-season. Follow the dosage on the bottle for your pool volume.
Metal sequestrant: Prevents staining from iron and copper while the pool sits. Especially important if your fill water has high metal content.
Scale inhibitor: Optional but recommended if your calcium hardness is on the higher end. Prevents calcium deposits from forming on surfaces during winter.
Brush the walls, vacuum the floor, and clean the waterline. Any debris left in the pool becomes food for algae over winter. Clean the skimmer baskets and pump basket.
Clean or backwash the filter thoroughly. For cartridge filters, remove and deep clean or replace the cartridge. For sand filters, backwash and rinse. For DE filters, backwash and do not recharge (leave the grids empty for winter).
Lower the water 4-6 inches below the skimmer for mesh covers, or 12-18 inches below the tile line for solid covers. This gives room for rain and meltwater without overflowing. Do not drain the pool completely. The water weight is needed to hold the liner in place (above ground) or prevent hydrostatic pressure damage (in-ground).
This is the most important step for preventing freeze damage. Use a shop vac or air compressor to blow water out of all plumbing lines: skimmer lines, return lines, main drain line, and any feature lines (spa jets, water features).
Plug each line with a winterizing plug (expansion plug) after blowing it out. Add pool antifreeze (propylene glycol, non-toxic) to the skimmer and any lines you cannot fully clear. Never use automotive antifreeze.
Remove all drain plugs from the pump, filter, heater, and chlorinator. Open the air relief valve on the filter. This allows any remaining water to drain out so it does not freeze and crack the equipment.
For saltwater pools, remove and clean the salt cell. Store it indoors. Disconnect the controller if possible.
Store removable equipment (pump, ladders, handrails, skimmer baskets) in a garage or shed if possible.
Secure a winter cover tightly over the pool. Solid covers keep out debris and sunlight but need a pump on top to remove standing water. Mesh covers let rain through but keep leaves and debris out.
Make sure the cover is tight and secure. A loose cover can blow into the pool and become a breeding ground for algae underneath.
Log your closing chemistry with Pool Clarity so you have a baseline when you open next year. Track every test and see trends over time. Free to use.