Thanks Ted. When I put suction on the skimmer port, water will go down on both ports in the skimmer but will come back up. The water level is about 6" below the skimmer door or the tile line. I was hoping to plug the MD port in the skimmer with rubber plug and make a rubber plug with a valve and blow water in the skimmer port and close one by one the drain plugs in the pumps, heater and then move to the supply ports and plug them when they bubble. I thought since water will go out where there is least resistance there in less back pressure on the return ports than there is on the MD (it is deeper - 9') and as I close all the returns I can then look for bubbles in the MD line. What are your thoughts in regards to not being able to blow the whole system form the skimmer? I wish I had a schematic of how this thing was plumbed. The pool is over 25 years old but I renovated the coping, tile and plaster.
Regards
Amir
P.S. I wuould have ordered the expand-n-purge plug except it was sold out at the only place that was listed in the post you mentioned.