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With an open system (no expansion tank) you'd need a non-ferrous pump (SS or bronze) and some open area so that the water can expand and contract without bursting pipes.
Better to use a small expansion tank... although if you could do a simple gravity loop then you could skip everything (pump included) but you'd have to provide a continuous piped path up and then back down for the water. It could handle smaller laterals but no dips or they'd form thermal traps.
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