Every time you run the tank dry, even for a short time, or have to prime the pump because it loses prime, you are doing damage to it. If you insist on running it that way, at least put a good check valve in line so as not to lose prime. Bottom line, a pump run this way versus the way it was designed to run is much more likely to wear out sooner than it should.

Scott -

I believe the item you need is called a "foot valve". You will likely need to adapt it to the 3/8" pipe threads that are at the end of the Vetrano hose. A Google search for "foot valve" will be revealing.

Keep in mind that you want to minimize the additional "strain" you impose on the pump. A pic of your current setup would be helpful.

Yes you can run a rotary from a jug, but as Chris points out, you can burn up the pump if you run the water tank dry. Having said that, I know someone that ran a 3 group LM from a water tank, if you keep you water bucket above the pumps horizontal plane you will have some slight positive pressure but again, run it empty and you may fry your pump. The OP is from New Zealand, I cannot suggest a location for the check valve out there, but here in the US you can get them from McMaster, Grainger, maybe even Lowes hardware. Any plumbing supply store should have them; just ask for a one way valve or a check valve.