I use this same concept to piggy back 3 shop vacs together to get more suction once. My boss brought his boat out of the water this year with-out pumping out the septic tank. Of course we didn't want to ruin a shop-vac bu pumping sh** into it, and we were told that one shop vac didn't have enough pull. It worked great unfortunately we didn't get any pictures. Happy Sucking!!
Step 1: Materials
1) Vacuum with a hose
2) 5 gallon water jug (Can be a bucket, but this requires more cutting and sealing)
3) Utility Knife (or equivilent)
4) Length of hose, or vacuum tubing
5) Duct Tape