inward bulging of side walls on rectagular metal frame pool

[AnnaK]

The only large metal fram pools I'm familiar with are the Intex ones used for dock diving competitions. On those, the sides bulge outward and the posts sort of curve inward. These pools don't have solid sides though, just posts.

[madwil]

my old intex kinda got a small waterdrop effect while filling- the bottom edges pushed out as water built up in the pool, making the top diameter slightly smaller than the bottom- if this is what you're talking about, it's normal
Make sure the posts are straight, and the pool is not leaning one way or the other- all sides are sloping inward slightly from bottom to top, not all leaning left/right...