Swimline 4' x 5' Equalizer Pillow, 133002

The Swimline 133002 is a 4 foot by 5 foot equalizer pillow, the air pillow that goes under a winter cover before the pool is closed for the season.

What it is for

Water expands when it freezes, and a covered pool left flat gives that expansion nowhere to go except sideways into the walls. An inflated pillow floating in the middle gives the ice something compressible to push against. At the same time it lifts the center of the cover, so rain and melting snow run outward to the edges instead of collecting into a heavy pond in the middle.

Inflating it

Use a pump or fill it by mouth, and stop well short of firm. A pillow inflated hard has no give left when the air inside warms up, and that is how they burst partway through winter. Around two thirds is the usual advice.

Sizing

This is the 4 by 5 size. Larger pools are often closed with more than one pillow so the cover stays supported across the whole surface.