The biggest issue is that we currently have a circulator pump in every apartment so we'd need to devise a way to get backup power into every bathroom.
Assuming the circulator pumps are part of the building heating system, not hot water circulation for potable hot water.
Are the circulator pumps for local heat distribution in each apartment? Or, are they to pull building heating water up to each apartment?
If they are used to pull heating water up to each apartment, could they be overpowered by a single higher pressure pump powered off of the emergency generator system feeding the heating plant. Not ideal but would provide heat during extended outages. Motor operated valve(s) would isolate the pump during normal operation.
