connorbenton

Thanks for the info on your setup - my proposed setup is pretty much the exact same as what you have (pipes well below frost line, extra insulation on everything that's above). Realistically the only scenario where it seems like I could run into danger with a setup like yours is where there's an apocalyptic combination of: 1. Multi day power outage 2. Multi day cold snap 3. I'm not around to manually drain the system myself And I think setting up a generator + battery backup to run the pump would take care of point 3.

Given the massive added complexity of glycol system maintenance (mixing, filling, draining, disposal) plus the slightly worse performance of a glycol system, I would by far rather bite the bullet and prep a culvert mid run and install a frost protection valve at #2 if that's what I have to do to avoid glycol. Anybody else with any different setups?

I can't find any guidelines / best practices regarding frost protection when the supply/return pipes to a monoblock are buried. Quite a few people with units placed close to a building seem to have the scenario I've sketched out in the upper section, where a frost protection valve gets put on the low point of the supply and return (only sketched one line for clarity). However, in my case, the unit can't go against the building, and actually has to go on the other side of a small walkway, so there's pretty much no choice but to bury the supply and return pipes. In theory, putting a frost protection valve at the #1 position I've sketched seems to be just be a waste of money, as in the best case it would simply drain some water out of the unit (provided it's placed lower than the unit's internal pipework). Putting a protection valve at the #2 position seems like it would be the 'safest' option, but would seem to require leaving some sort of culvert / access shaft in the middle of the pipe trench run (sketched the 'ground line' with the dotted brown line, showing the shaft that the #2 valve would have to go in), which seems like a lot of additional complexity. If the pipes are buried below the frost line, could the internal water then be always assumed to be above freezing, and keeping the above-ground outside water in the unit above freezing through natural convection, so that no frost protection valves at all are actually needed? Or at least if the buried pipe water is 'safe', maybe the frost protection valve at #1 would be 'good enough' since it drains out the only above-ground parts of the system (perhaps a mirror would be needed at the house entry)? Curious how you all have seen actual examples of frost protection in systems with buried pipes.