Cleaning windshield wiper system T shaped valve

I have a problem with the T shaped valve for my '87 E30. It's part of the windshield wiper system - no. 15 here:
I just changed it (bought it at dealers) a year and a half ago, and it is blocked. There are two holes in it, and water is not sprayed on the windscreen, it escapes trough these two openings down at the engine. Drivers side does spray a little, but on the passangers side nothing.
I only put demineralised water in it, and it is not used often.
What is the reason that BMW fitted valve here? Can I fabricate one out of brass or copper tubing?
Or is there a way to clean this, and how?
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/__/ / \ ** Registrovani korisnik Linuksa #291606 **
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