Baseboard pipe in basement: over or under door?

I'll leave the "under/over" question for others. However, I will comment on your reluctance to sweat copper if the "under" option is chosen.

Consider using SharkBite connectors.

Yeah , use those pieces of crap . OK , it might have been the wrong situation , but they used sharkbites to repair my water supply after the city ripped it up looking for a sewer line blockage . A year or so later we had to dig up the sidewalk again and do the repaor correctly with sweat fittings .

I replaced an old waterline with PEX and sharkbite and have had zero problems. Though it can be used within concrete there is a specific way it needs to be wrapped to protect it. My /guess/ is the problematic sharkbit used in concrete was either not wrapped or at least not wrapped properly. I like the idea of pushing it through a PVV pipe though...no breaking up concrete if a problem and no fittings underground.

Put it under the floor under the door. Sweat the tubes together above ground, then drop them in. and sweat them into the system

Not for burried connection on hydronics.

I'd use them to connect the copper to pex above ground on both sides. Use the pex underground as it will flex where needed to make the run.

Or just do the whole job with pex, saving all the joints and the cost of copper.

Inside a wall is OK according to the instructions. Underground requires special treatment.

I've looked at the design. My gut sense (back then) was they would not last very long. Thanks for the field report.

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