Dave, I think your best bet to be safe is to continue shutting the system down, blowing out lines and draining the pump. In an un-insulated building even with an electric heater it may still freeze and you also risk freezing in the event of power outages as mentioned. I would try to gear the system for ease of draining, maybe remove the plug on the pump and thread in a small brass ball valve to ease in pump draining.
People up here that have weekend cabins go through the same procedures. We are usually safe between May and September although last night was down to 5c. :rolleyes: It's serious business here for those of us that live out in the country if power goes out in winter. Woodstoves and generators are a must. I still have pipes freeze occasionally even with all the precautions. Heck, I'm happy if my vehicle starts in the morning, block heater and all.
I think your method is still the best, although a pain in the butt as you say.
