I am changing a pressure tank for a catchment water system (here in Hawaii some rural houses do not have county water so we catch water from the roof and it is stored in a tank , in this case, below the house so it needs to be pumped up to the faucets. My question is, after I disassemble the pump and pressure tank, which will spill the existing water out, then replace the tank and re-solder it together, how do I prime the pump when the system is closed? Hope there is a simple, or at least doable answer. Thanks [email protected]

Assuming this is a jet pump of some sort, there should be a plug, or possibly a pressure gauge, at the top of the pump impeller housing. Remove it, pour in water until it runs over, replace it, and start the pump.