I have an AquaPro Pro500 heat pump with perhaps the worst user manual of any product ever produced. The manual states that I should have a Hartford loop in the plumbing. I have some idea of what a Hartford loop is, but not entirely sure. Can someone please describe it to me, and more importantly what it's purpose would be for a heat pump. What I found online is this: "Helps to prevent water from siphoning out of the heater when the pump is turned off.". From my setup (above ground temporary pool) I cannot see how that would happen anyway. Thanks in advance for any help you may offer.