This is an easy to print design for use with a water tap. The design is based around a metric fine thread 24x1mm, AG M24 but can easily be modified in OpenSCAD to fit different sizes. It is not designed for limiting waterflow but rather to increase flow by creating a vortex. So for most cases you only need to open the tap only half way if not less. It has no filtration element, so clogging shouldn't be an issue in the foreseeable future.
The best part is: just use your favourite printer and standard settings or a service (3D Hubs), hit print and around one hour later you have the nozzle ready for installation.
If you would like me to print it for you, just hit my profile on 3D Hubs:
By the way: students get 25% off ;)