GE Water Softener Not Draining

[Phil S]

This should be simple, but I can't figure it out.

My water softener isn't draining the brine tank during recharge.  I checked the venturi; there is suction there if I remove the tube.  I disassembled it, and checked all the screens for blockage; it's all good.  I checked the tube, and it is running clear.  

But when I hook it all up, it doesn't work.  There is weak suction at the other end of the tube; and it doesn't move any water.  I put the end in a cup of water, and it took an hour to drain maybe a few ounces. I guess there could be some vacuum leakage at the connection, but it looks good. 

I can't figure this out.  Any other suggestions for things to try?

[Phil S]

Follow up:

Another issues appeared: salt in the house water supply. 

And here I started to figure it out.  The drain isn't working.  I put the water softener in "rinse" cycle, and there was a light trickle of water in the air gap, unlike the usual gushing sound.

So, I disconnected the drain line, and what do you know, there's some kind of plastic debris in the drain outlet.  Cleaned it out, and everything is working well.  

What the debris is, I have no idea.  This is the second time I've found random junk in the drain line of an appliance; my washing machine had a small lump of metal jammed in the drain pump.  Where is this stuff coming from?  It must have gotten there at the factory.