tandem TC-06s 'inheritance'

[Deleted User]

gee, can you guess what happens to the prvs when the pump is shut off?

and the real question is this; lead/lag operation, and within a year of installation, the 1st section on the left boiler return had cracked/leaked, and a warranty replacement was done by another. we just picked up the maint cont and now have another/same cracked section. does anyone know of a history of TC-06s doing this, or would you believe it to be just a 'cold' return problem? and yes, we are going to re-pipe it according to the diagram on the re-pipe pic