How about circulating propylene glycol instead of water, inside a copper
tubing load coil? Nontoxic, basically nonconducting in case of a leak,
and pretty cheap (Sierra antifreeze is about $7/gallon here in the US).
It's a little viscous until it warms up, and doesn't have the heat
capacity of water, but should be safer for you.

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Regards,
Carl Ijames carl.ijames at verizon.net