not a post and run, but a no wifi. I tried to get my arm down the hole but I was lucky and it did not fit, so got my wife to put her arm down the hole. She found there was an elbow at the bottom that we could not see. I got a better flash light and a long stick and prodded around, and could make out the elbow. On the elbow I could make out that there were two trails of yellow adhesive that had run down and formed a large X. When you poke it with a stick, it looks and feels like a solid grid.
So, in the end, by flushing the elbow with a strong steam of water, it became more visible, and not the issue I thought it was.
Thanks to all for your imput, especially comments that it should be a straight path to the tank, and also that Keystone systems may have an elbow.
