Hartford Loop

[GreatCanadian]

Hi all,
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.
GC

 

[JasonLion]

The idea is to keep the water from draining out of the heat pump even if the pool is drained. You run the pipe above the top of the heat pump and also above the normal pool water level and then install a vacuum breaker valve. That prevents a syphon from forming, which would otherwise drain the water out of the heater.

 

[GreatCanadian]

Thanks for the response. Why would I want water in my heater if my pool was drained?

 

[JasonLion]

If the heater turned on while there wasn't any water in it at all it could be seriously damaged. It would take a major failure somewhere else for this situation to come up, say a large leak, but if that did happen a Hartford loop could save your heat pump. Some heat pumps have hartford loops built-in, others depend on water flow sensors to shut them down when there isn't any water. Apparently yours would like to have an external loop.

 

[GreatCanadian]

Ahhhhhh...now it's starting to make some sense. That's the first explanation I've heard that made me realize the benefit of a Hartford loop. My pump will shut down with low flow, but I guess the loop is like insurance.