I seem to have mine dialed in now, but what I did once was checked the OG of my runnings. Saw that there was way to much sugar left and heated up more water and sparged some more.
Also, adding a cheap sight tube to you kettle will help you check what your levels in the kettle are up to.
I used 2 elbow compression fittings attached to each outer with 1/4" plastic compression tubing. The same as they use in ice makers. It's semi transparent and I find, quite readable. Since this was the boil kettle I placed the bottom on up a bit in the kettle, but the one on my HLT is lower and hasn't melted. I just placed some tinfoil as a heat shield near it to be safe.