I don't see an advantage over using a compressor to blow out the system.
Floe Induratec 636 12v drain down system
The kit takes around 20 minutes to fit to your vehicle and in six easy steps your vehicle will be fully drained down.
Step 1: Drain your water heater
Step 2: Close water heater dump valve and all taps
Step 3 : Switch the Floë 636 on to activate the air compression system
Step 4: Open each tap in your caravan or motorhome individually, including the shower, until all are drained.
Step 5: Switch off the Floë
Step 6: Leave all taps open to let the air circulate