I once cleaned the nozzles out with a compressor and the small "balls" directing the waterjet, popped out. I never saw them back!
So I clean them very regularly with a "special, stiff stainless steelwire".
In fact it's a hair I "borrowed" of my poor steelwire brush, just pulled out
with some plyers.
To keep your steel brush in condition: keep it (the hair) in a small filmbox ( the brand
of this is not important ) in your glovebox.
BTW these little pumps costs only € 26. For a few cents more, replace the
rubber washer under it to.
You will be pleased every time you use the windshieldwashing installation
( and you will do so mutch more!).