Take a breath. I raised my irrigation pump about a meter off the ground. Constantly loosing prime, I check, rechecked and replaced the non-return valve on the inlet side. Online research pointed to the outlet siphoning out the prime due to the height. This vacuum breaker on the outlet side solved the problem 100% by allowing some air into the system, without draining the prime, as the water in the pipe dropped down to ground level, whenever the pump is switched off. No more priming issues.
