"Mike" wrote:

Looks like the simplest suggested solution is to use heat tape. I was
hesitating to use them because of the safty concern. Are they safe?

A plumber I know says no. A Home Depot employee told me they no
longer sell some forms for liability reasons. Another solution is
to put a thermostat near the coldest part of the pipe (eg an EH38
"Easy Heat thermostatically controlled device" ($10.99 at Lowe's))
in series with a solenoid valve from an old washing machine that
lets some some water flow out of the pipe when it's too cold.

Nick