If the siphon is on the supply side (and the low pressure side as well) it only makes sense that pump rebelled when the sand tried to make it's way through... I imagine it ate up the passages .25 times as fast as it ate paint?
If I'm reading your post correctly thats not how it worked. The water was pumped through the pressure washer, and out the hose/gun as normal. There was an attachment to the gun, with a tube down to the media. The pressure of the water going through the gun, pulled up the media through the tube, and out the media nozzle mixed with the water.
But anyways, Apache, I think thats a great starting point! That is where I am at currently too! Still working on removing the paint on the top, and back of my cab!
