View source for ShuT/DudShemesh

Question: may I use water heated in a "dud-shemesh" (solar water heater) on Shabbath?

It is forbidden to use water which was "cooked" on shabbat.  So for instance,
if one had a gas-flame water heater, it would not be permitted to use the hot
water on shabbat.

However:
# A "dud-shemesh" heats the water by ''direct'' application of the sun's energy, and heating by direct solar energy is permitted.
# The cold water coming into the heating unit does not mix directly with the hot water, and so does not "cook" indirectly.

Given this, it is permissible to use hot water from a solar water heater on shabbat.

{{devar}}