After getting tired of paying $30-$40 for a backflow preventer kit every year due to the poor quality and design. I decided to make my design my own backflow preventer.
This design has been modified and reinforced to fit Febco 765 3/4 system. (see the image of the original backflow preventer).
I recommend printing with at least 80% infill, 100% is even better to prevent water pressure from finding its way through the hollowed areas. Printing support it needed.

0.100

50

After getting tired of paying $30-$40 for a backflow preventer kit every year due to the poor quality and design. I decided to make my design my own backflow preventer.
The design to fit Febco 765 3/4 system. (see image of the original backflow preventer)
If possible I recommend printing at resolutions 0.100 - 0.150 because of the parts have threads. I also printed using ABS 50% infill.
Then remove all the metal parts and the rubber gasket and o-ring from your old and broken backflow preventer and install on the 3D printed parts.
The metal pin can be removed by heating it up with a lighter or small torch.
I'm sure it would look great using a resin 3d printer.