Originally Posted by transmitterdan
Air conditioner pumps are not self priming. Thus the hose from thru-hull to pump inlet must be below the waterline and be flat or slightly down hill. You want water to flow by gravity to the pump inlet.
Ours are (self-priming). The OP's probably could be too if they wanted them to be. Some AC A/C are setup to run DC powered pumps, of which many are self-priming; if you want a self-priming AC powered pump
those exist too.
The only non-self-priming pumps we have aboard are for our pressurized fresh water system. I find them it inconvenient when they need priming. I suppose one could argue that the submersible bilge
pumps are not self priming, but I've never needed to prime them
The OP's original question was about head
supply, not AC, but the same applies -- except I'm used to head
supply being DC.