How to store Thermosyphon water heater when not in use?

[Colorado_Al]

I am installing a Thermosyphon water heater on my home in Baja. Next month we will be traveling for a month. We're going to shut the water off while we're gone.
What's the best way to leave the water heater while we're gone? Should we drain it and leave the expansion valve open? Or leave water in it? Or other suggestions?
Thanks!
Al

 

[OzSolar]

Best to drain it and I'd even go as far a throwing tarp on the collector. No need to let it bake itself for no reason.

 

[Shimmy]

Personally I would leave it as-is. Mine is a pumped system, but the expansion valves will deal with over heating easily enough. I've left my system in Hawaii as-is for ~6 weeks during the summer. I did have to replace the swing-gate check valve with an inline check valve though.