I have a clip in cover. Its the only plug like itWhat's underneath it? Could be an anchor hole for a safety cover.
No its too small and an umbrella wouldn't fit as the pool shed is a couple feet behind it. Another guy speculated it could be to drain water that could collect around the outside of the pool if the liner leaked or to check for leaksOr a socket for an umbrella.
Once the rain stops I will take it out. Maybe it is for an umbrella. I have full sun with no shade back thereLooks exactly like a plug for an umbrella/volleyball pole sleeve although it looks like you don’t have the sleeve part
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Can you remove it?