I woke up to a piercing alarm - the sump pump water level was too high. We figured out the end of the discharge pipe was frozen outside so heated it by inserting a hose spraying hot water. The ice melted but the sump pit didn’t empty. I started trying to empty it with small pails but after 30 mins. the water level in the sump pit seemed to have barely gone down. Any tips on why the manual drain would fail?