Can I leave eyelet uncapped?

[BigDave]

Last year, did you remove the return eye and cap it from the inside?

[Steveromo]

No, I did not remove eye, but I did cap it from the outside.

[BigDave]

I'm pretty sure the idea is to remove the eyeball and cap it from the inside - that way the fitting that goes through the pool is dry and won't get cracked when water freezes inside.