During our 2-day Rural Water Supply Operations Seminar in Morrisvale, WV we tried out a couple of things using vacuum tankers. One of the "things" was off-loading water through 5-inch LDH by only the rig's vacuum pump. Because the vacuum tanker operates around 15 psi, there is limited pressure by which to push water through hose using only the vacuum/pressure feature....thus the importance of using the 5-inch hose in the test that we did. The 2000-gallon tanker offloaded its water in 2.17 minutes (922 gpm) through 100-feet of 5-inch hose and no elevation gain.

The set-up basically replicated an "open-relay" and showed another way of using these rigs. If you think creatively for a minute, the vacuum tanker could have been "sucking" water out of a stream or other source and then pushing it to the dump tank through hose....kind of like a big, slow-moving positive displacement pump. As long as the fire flow was under 750 gpm perhaps, the dump tank should have sufficient water in it for the drafting pumper to draft without cavitation worry.