Take the filter out. Cold won't warp it, but ice will.

Cold air alone won’t warp a clean cartridge filter element. The media and plastic components are usually fine down to freezing temps. The problem is water — if the element is even slightly damp, or if there’s standing water in the tank, ice expansion can distort the pleats and crack the housing.

So technically, if your filter is completely dry and your tank is drained, you can leave it in over winter. But it’s a risk that saves you about ten minutes of work. Filters are cheap to replace; warped pleats aren’t always visible until you run the system in spring.

Pull it out, give it one last rinse, let it dry fully, and stick it in a garage or basement. That’s the safe move. Future You will thank you when the pump actually works in May.