Coco coir and salt buildup?

Anyone know if it is typical to need to flush coco? I have 50/50 coir and perlite substrate. I top feed with 2ea 1/4 in tubes per pot. My thought was that I was basicly flushing the pots as I water them. My on cycle is 10 mins each time so I get a lot of runoff. Anyone with coco experience?

i've heard that salt buildup is not a prob in coco... but i don't know from exp...

i'd like to try it though, where can i find the coco coir? i didn't see it at lowe's...