Hot water pipe keeps bursting (2 kids and no heating in November)

[oz-plumber]

Why don't you find out when the system was installed and how long the pipe warranty is.

If it failed within the warranty - claim the damage and repairs off the manufacturer.

They may take some more interest in the situation if they know they are liable for the repairs.
As for the airlock excuse - I don't buy into that one ....twice.