Well, they called it a Hartford loop, but it's not one. It's become common to call any sort of U-shaped piping arrangement near a piece of equipment a "Hartford loop", I guess because they can't think of anything else to call it. (I'm a Master Plumber, so I'm not just saying that.)

What they are try to do is create a point where any gases from a inline chlorinator won't flow back to the heat pump. It's not necessary to have one, unless you have an inline chlorinator. Even if you do, if you install the check valve as show, it's not necessary to have 2 U's, one point up, and one point down. You just need the check valve on the left leg of the upside down U.

They do show the heat pump on a bypass loop. I'd seen this thread, and decided to stay out of it, because I'm so far behind. But, if I were doing it, I'd maintain continuous 2" piping, and put the heat pump on a 1.5" bypass.

Do NOT use Chinese made ball valves for your piping -- I've gotten burnt badly over the past few years using Chinese made stuff from Lowes, even when it was American branded!. The Hayward pool valves are OK. I think these valves are OK:
King Brothers WLT-1500-S 1-1/2-Inch Slip PVC S-40 Commercial Ball Valve, White
King Brothers WLT-2000-S 2-Inch Slip PVC S-40 Commercial Ball Valve, White
Industrial grade valves from Hayward or Spears are fine. One caution though: to winterize a ball valve you MUST put the valve handle at a 45, neither open or closed fully. Otherwise, you trap water in the valve body.