Thanks for helping the new guy. Its great to actually see a little consistency to the questions. I will do a little more research. As for the Tiff idea, it was mentioned to me by a Tiff salesperson that technicians use it to test methane gas emmisions coming from manhole covers. I have tested poor venting using the Tiff and although very unscientific, the results seem to show that drains with very poor venting or none at all will trigger the tiff at a very low sensitivity (1 1/2 lights). Maybe its all voodoo. Eric from New Hampshire