A pool contractor told me that I need to install a drain spigot on either the fill or return pipes for my roof-mounted solar collector to prevent the water from freezing and damaging the collector. Is this true? It's my understanding that water is only in the collector when heating is needed (solar valve open and pump running), and drains by gravity at other times.
He said this is needed since there is a check valve on the solar return pipe. But isn't that normal? This check valve/solar return is between the solar inlet/bypass valve and the gas heater. That seems appropriate to keep the solar from filling (backwards) when the valve is set to bypass solar.
There is another check valve on the other side of the solar inlet/bypass valve where water comes in from the pool, but I'd think the solar collector would drain towards the gas heater and on to the spa/pool, not backwards.
Note, this is for an area of Southern California that does very rarely get below freezing in the winter, but only for brief periods during the night. So I don't think I need to be concerned about water in the pipes below ground.