This is my quick solution on a jet-type inlet for Bestway pools. I do have a medium-sized oval framed one where the thread diameter of the inlet ist 86 mm. I separated flange and nozzle for quick and easy print. Just push the nozzle through the flange.

Larger pool models probably use 38 mm (1.5 inch) hoses so the inlet diameter can be bigger!

There is no need to glue the nozzle. You can turn it to your linkings (slight angle downwards recommended to get the water spinning) and it will hold its position from the water pressure.

I printed flange on 102% and nozzle on 101% to get a perfect fit. The nozzle need a bit of support.

I recommend using a pump with at least 1000 gal (3750 liters) per hour. The cartridge pumps delivered with the pool sets will struggle to get the water moving (depending on your pool size).

Benefits of a jet nozzle:

• Water spins in pool giving protection against forming seaweed
• Easier cleaning of ground debris (will collect in center of pool)
• Auto-rake on water top possible (if you don't like to use a skimmer)
• Pool walls stay cleaner (no air bubbles and lesser calcification)
• More fun :)

Maybe I will add additional nozzles to this thing (fountain, etc.).