Yes, you want the bottom (lowest) part of the hartford loop at least 2 to 3 inches above the water. More is good, but not necessary.Usually it comes down to where it is and how it is getting hidden. Many times it is dependent on how thick the decking is, as to how far up we can have it.
With an edge pool you dont have to worry about the water level getting higher.

What is the Hartford loop feeding?

Many thanks for your response. The Hartford loop is the last thing except the salt chlorinator and a two-way valve in the return line to the pool in the pool shed. I can go higher than 2-3 inches, but logically I can't see that it makes any difference once I pass the water line...

Also - electrical supply for chlorinator will be immediately above the vacuum release valve at the top of the loop - is that OK? I am assuming that air goes in but nothing will come out... Are vacuum release valves reliable, or should I design to allow easy replacement?

What type of salt chlorine generator are you installing?

I am confused as to what you are trying to do.

Thanks for your interest, but why does it matter? I think it is a Compupool... The chlorinator is really not related to my question, but you asked 'What is the Hartford loop feeding?', so I gave a quick breakdown of the layout. I am simply putting a Hartford loop in the return line to the infinity pool to make sure that water cannot back siphon from the returns into the edge trough.....

Sorry - not sure what I said that gave offense, it certainly was not my intention. I am grateful for your input.

I will have a check valve as well, but my view is that sooner or later a check valve will fail, probably at the worst time possible when nobody is around. Then the entire pool ends up in the trough/garden/undermines pool. Thus I want a check valve AND a Hartford loop as a belt and braces approach. Just trying my best to get this thing right...

I don't understand your comment; I have read a lot of your posts and know that you know your stuff, but if the top of the loop in the return pipe is above the level of the water in the pool and the valve in the top of the loop admits air when under suction then surely it is impossible for siphoning to occur - that is the whole point of a Hartford loop. What am I doing wrong here? Anyone else care to comment?

I think the loop would be fine/needed if there was a vacuum breaker to stop the siphoning action. The loop must be above the pool level height.

A loop by itself won't stop a siphon. If the gasket on the check leaks, the pool will siphon to the catch basin, even if the loop were 10' above the pool.

It sounds like, from other posts, a single pump is filtering and driving the negative edge. The salt cell is the last thing at the pad. Prior to that is your check valve or in your situation, the loop with a VRV and then the heater.

Scott

Thanks Scott. My current design of main circuit has drains > suction line > 3-way-valve > pump > two-way valve > cartridge filter > 3-way-valve T out to solar panel circuit > 3-way-valve T in from solar panel circuit > Hartford loop with VRV at top > chlorinator > two-way valve > check valve > pool returns...OK? (The last two-way is to isolate the chlorinator when I need to replace the cell - I am assuming that the check valve alone might not be sufficient when opening up (??). )

I am in fact using two intelliflo VS3050s, one to drive the negative edge circuit, which has its own returns into the pool, and one for circulating the pool water ('main pump'). However, if a pump dies here it may take weeks to get it fixed/replaced, so the first 3-way before the pump is both to isolate the pump when needed and to connect to the edge-circuit suction line so that the main pool pump can do both circuits if the edge pump dies; if the main pump dies I can simply swap the pumps over as they are identical. As there may therefore be times when the main pump is in the same circuit as the trough I am putting Hartford loops with VRVs at the top in the returns on both circuits.

Isolation valves on the suction side and return side plumbing should be enough with check valves on the pump discharge ports.

The solar panels are going to fly and or tear and destroy the plumbing. As you said before, the hurricanes are inevitable. Its your money but it's still a bad idea. The heat pump, if power is available, is a simpler and more durable idea unless you are power restricted.

As my friends have said, the panels will stay flooded unless you empty them. Set on sand, they will need to be strapped down at each end and a strap across every 5 feet of each panel.

Beyond that, I can't think of much more you could do.

Scott

Obviously with a VRV no problem.
I didnt catch that on your original post.

The main thing we use Hartford loops for is for air lines, so no VRV would be used.