I believe the soap would only work on a pressurized pipe, not one in vaccum. What about a bit of dye (food or other) at the vaccum areas that you want to check? If the discharge water turns color then you know the dye was sucked in.

www.hoosierpondpros.com


http://www.pondboss.com/subscribe.asp?c=4
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).