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I am having a weird issue. System has worked fine for a over a year until recently. Problem now is Zone 1 will start and run as normal, as soon as zone 2 starts, it starts normally and then begins to lose pressure rapidly and will completely shut down and the pump will lose prime. After priming again, the only way I have found to keep it running through all zones is to open the hose bib right above the pump, the hose bib will keep a very strong stream and each zone (5) will work fine, good pressure even with the hose bib open. If I close the hose bib at any time it’s like the system chokes out/loses pressure no matter which zone it is in and the pump will prime. Any ideas what may be causing this??