Pool Pump Winterization: Every Drain Plug and Why It Matters

Water expands roughly 9% when it freezes. A pump housing that still holds a cup of water when the temperature drops below 28°F will crack — not might crack, will crack. The volute, the basket housing, the trap body, the impeller — any water-retaining component is at risk. A proper pump winterization is a 30-minute job that prevents a $400–$700 replacement come spring. Here is every step, every drain plug, and the order that matters.

Before You Start

Confirm the pool has been properly prepared for winter: water level dropped below the skimmer and returns, pool chemistry balanced (high alkalinity and slightly elevated chlorine), and the pool covered. The pump winterization happens after the pool prep, not before. You need the pump running briefly to help clear lines, so do not start shutting things down until the water chemistry is set.

Drain Plug Locations by Pump Component

Basket/Trap Housing Drain Plugs

The basket housing — the front section of the pump where the strainer basket lives — has one or two drain plugs at the lowest point. On most Hayward pumps, you will find them at the 6 o'clock position on the front face of the housing. Pentair models often have a single plug at the bottom center. These must come out first since this section holds the most water by volume.

Volute (Wet End) Drain Plugs

The volute surrounds the impeller and houses the main water passage. On most residential pumps, there is one drain plug at the bottom of the volute body. It is often hidden behind the plumbing union and easy to miss. Remove the basket housing plug first, then rotate under the pump to find the volute plug. Use a flathead screwdriver or 1/4-inch drive — most plugs are 1/8 NPT.

Motor Drain / Air Vent

The motor itself does not hold water if the shaft seal is intact, but the seal plate area can trap a small amount of moisture. On rear-access motors, check for a small drain hole at the bottom of the mounting bracket. If present, clear it.

Full Winterization Sequence

1. Turn off pump and disconnect power at the breaker — do not just use the timer. Lock it out if possible.
2. Close suction valves — this prevents water from flowing back from the pool while you work.
3. Open all drain plugs — start with the basket housing, then the volute. Let water drain completely. This takes 2–3 minutes.
4. Remove the basket and lid — store the basket indoors to prevent UV degradation.
5. Blow out the remaining lines — use a shop vac in blow mode or a compressor at under 10 PSI to clear any trapped water in the suction and return lines leading to and from the pump. Do not skip this step in hard freeze climates.
6. Leave the drain plugs out — store them in a bag, but leave the openings clear so any residual moisture can evaporate. Reinstalling plugs traps moisture.
7. Cover the motor — use a fitted cover or a breathable bag to protect the motor from rain, ice, and debris while still allowing ventilation. Do not use a sealed plastic bag — it traps condensation.
8. Disconnect automation wiring — if your climate is severe, disconnect and label the automation and sensor wiring. Freezing wiring can crack insulation.

Variable Speed Pump Considerations

Variable speed pumps have electronics in the motor housing that are more sensitive to moisture than single-speed units. Check the manufacturer guidance — some VSPs specify that the motor assembly should be stored indoors in climates below 0°F. The drain plug procedure is the same, but pay extra attention to the motor cover.

Spring Startup Check

When reopening, reinstall all drain plugs before turning water on — obvious, but frequently missed in the rush of spring opening. Check the shaft seal visually before the first run. If water sat in the seal area all winter, the ceramic face may have surface corrosion. Turn the pump by hand (remove power, then rotate the impeller shaft) to confirm it spins freely before applying power.