Why does my Malvern drain block at the same time every year?
Seasonal recurrence is the signature of a root problem. Tree root growth accelerates in warmer, wetter months, so a root mass that was cleared last year regrows and reaches blocking volume at roughly the same point in the cycle. The underlying cause is the entry point — an open or cracked joint in the clay line that was never sealed. Until that is repaired or relined, the annual pattern will continue no matter how thoroughly it is cleared each time.