What are these "features" in my pool walls?

[mackguy]

My pool has these little holes all the way around... maybe 6' spacing or so. There seems to be a short threaded portion.. I can put a finger pretty much all the way in without bottoming out. Also, two of these little "star" shaped features, and one portion where there's 4 holes in a vertical pattern. Any clues?

 

[woodyp]

Ya' got me!

 

[Clayswen]

Cr*pload of returns? Cleaning system?

 

[jblizzle]

Our 70s pool has them too. And wife had them growing up. It was a cleaning system where hoses would be hooked up and they would move all around from the water shooting out the tubes. (Apparently fun to spray at each other) Idea was to keep the dirt suspended to get filtered out ...kind of like the in floor systems now do. Difficult and expensive to find the parts. I just left the holes and pipes as a backup return system.

 

[mackguy]

Interesting, yes our pool is 70's era.. guess the plumbing for these was capped off, as there's no water movement.

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