Pool Pump Winterization Guide — How to Properly Shut Down for Winter

When to Winterize

Winterize when your area is approaching sustained temperatures below 32°F. In most climates, that means October–November. In mild climates (Zone 9+, most of Arizona, Southern California, Gulf Coast), winterization isn’t necessary — the pump runs year-round. In freeze climates, timing matters: too early means an empty pool all fall, too late means risking a freeze before you’re ready.

The key date is your first forecasted hard freeze (below 28°F for several hours). Winterize at least a few days before that date.

Step-by-Step Winterization

1. Balance pool water chemistry 3–5 days before closing. Target: pH 7.4–7.6, free chlorine 3–4 ppm, alkalinity 80–120 ppm, calcium hardness 175–225 ppm. Out-of-range chemistry causes scale and corrosion during the closed season.
2. Shock the pool with a high dose of calcium hypochlorite or non-chlorine shock. Let it circulate for at least 8 hours before adding other closing chemicals (algaecide, winter enzyme treatment).
3. Lower the pool water level to below the skimmer mouth and all return jet fittings. How much to lower depends on your pool type and cover — consult your cover manufacturer, but typically 6–18 inches below the tile line.
4. Turn off the pump at the breaker. Not the timer — the breaker. Leaving power to the pump during the closed season is a safety issue.
5. Remove the drain plugs from the pump volute. There are two — one on each side of the bottom of the pump housing. Turn counterclockwise with a screwdriver or by hand. Let all water drain completely. Store the plugs in the strainer basket inside the pump housing so you know exactly where they are in spring.
6. Remove the drain plugs from the filter. Sand filters have a plug at the bottom of the tank. Cartridge filters should be removed, cleaned, and stored dry. DE filters need a full cleaning and the DE powder removed.
7. Blow out the suction and return lines with an air compressor (recommended) or shop vac (adequate for most residential systems). Insert the nozzle into the skimmer suction port and blow air through until no more water exits the returns. Plug the return jets immediately with expansion plugs as they blow clear.
8. Add antifreeze to any lines you can’t fully blow out. Use propylene glycol RV/marine antifreeze — never automotive ethylene glycol. Pour it through the skimmer after the lines are blown.
9. Remove and store the pressure gauge and any other sensitive instruments. Pool chemical exposure degrades gauge seals over a closed season.
10. Cover the pump housing with a breathable cover or tarp that sheds rain but allows moisture to escape. A sealed plastic bag creates a moist environment that promotes rust and corrosion inside the motor.

Freeze Protection vs. Full Winterization

In climates that occasionally dip below freezing but don’t have sustained cold winters, some pool owners use freeze protection (a temperature sensor that automatically runs the pump when temps near freezing) rather than full winterization. This works well for mild freeze climates (Zone 8, parts of the South). For regions with weeks of below-freezing temperatures, full winterization is necessary — freeze protection alone won’t prevent damage in sustained cold.

Prevention

The best freeze damage prevention is a proper winterization done at the right time. Don’t rush it and don’t delay it. Set a calendar reminder 2 weeks before your average first hard freeze date. Have all your supplies on hand beforehand — plugs, antifreeze, air compressor. A properly winterized pump has survived decades in freeze climates without incident. See the freeze damage guide if you’re dealing with existing damage.

Frequently Asked Questions

Do I need to drain the pool pump every winter?

If you live in a climate with freezing temperatures, yes. Any water left in the pump housing will freeze and expand, cracking the volute. This is non-negotiable in freeze climates. In frost-free climates (most of Arizona, Southern California, Florida), you can run the pump year-round and winterization isn’t necessary.

Can I leave my pool pump outside during winter?

Yes, if it’s fully drained. The motor itself handles cold fine — it’s metal and plastic that doesn’t crack without water inside. Drain the pump housing completely (remove both drain plugs), cover with a breathable cover, and leave it in place. Don’t cover with a sealed plastic tarp — moisture gets trapped and causes motor corrosion.

I forgot to winterize and we had a freeze — what do I check?

Before starting the pump: inspect the volute for visible cracks (especially around the inlet port and drain plug holes), check all union fittings and pipe sections for cracks, and check the filter housing. Then do a pressure test: fill the system, start the pump briefly, and look for water escaping under pressure. If anything is cracked, see the freeze damage guide before running the pump further.

What plugs do I use to plug the return jets?

Pool expansion plugs (also called winterizing plugs or Gizzmo plugs) are tapered rubber or plastic plugs that insert into return jet fittings. Sizes vary by fitting — most standard residential return jets take a 1.5-inch or 2-inch expansion plug ($3–8 each at pool supply stores). The skimmer gets a Gizzmo or a solid plug in the suction port.

Should I remove the pool pump motor for winter storage?

Not necessary if the pump is fully drained and covered. The motor handles outdoor winter storage fine. Removing the motor adds complexity and risk of reassembly errors in spring. Only remove the pump motor if you’re doing maintenance work over the winter (bearing replacement, capacitor swap) or if you have extreme winter conditions where the equipment pad is completely buried in snow for months.

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