Can a pipe burst from hydronic air lock?
I have baseboard water radiators and cast iron radiators. Can the water pipe in the baseboard radiator burst if it has hydronic air lock? New circulator was put in two weeks ago and then this happened.
The expansion tank and T&P relief valves should stop that from happening. Have you had a freeze maybe?

About 8.5 feet long. Was for sale. Now gone. May have another available in the summer.
This is one of my favourite shots from this set. The colours and lighting in this room were fun to work with.