Shower Drain Frozen [upd]

"When my basement shower drain froze, I didn't have a heat cable. Here’s what worked:

"My 5th wheel’s shower drain froze at 10°F. Since I couldn't run a heat cable inside the plastic underbelly, I poured a gallon of directly down the drain. Let it sit for 30 minutes. It slowly ate through the ice plug. Not a perfect fix (it left pink goo), but the water drained again. Deducted one star because you have to flush it 10 times before the smell goes away." shower drain frozen

Strange noises occur as air struggles to push past ice blockages. "When my basement shower drain froze, I didn't