I have a closed loop non pressurized system that randomly gushes out water at the flow center/tank area. It doesn't happen often (every six months?), but when it does, it releases several gallons (yes, gallons) of antifreeze. I have yet to see it happen, so I couldn't tell you the source of the leak. It just happened again, and lost so much antifreeze that my heat pump faulted. I added water to start it up, but I know I need to add propylene glycol to make up for the loss. I have a service contract, but I'm reluctant to call without knowing the source of the leak. Any ideas?