For especially tough clogs, use ZEP Commercial Crystal Heat Drain Opener. The special formula in this chemical drain cleaner generates heat to melt the tough clogs in your home. Eliminate clog-causing grease, soap scum and hair on contact with this lye drain cleaner. This formula is safe on all types of pipes and septic system, perfect for clogs in kitchen and bathroom sinks. Directions: 1. Remove as much standing water as possible from sink or tub. Make sure water in drain is cool. 2. Slowly pour 1- heaping tablespoon of Crystal Heat Drain Opener directly into drain. Do not allow product to contact any sink or tub surface or fixture. Damage may occur. 3. Add 1-cup of cold water to drain. Immediately cover drain opening with a bowl to avoid splash back. Do not completely seal, as pressure can build up. 4. Once drain has cleared, flush with cold water. 5. If drain remains clogged, repeat steps 15.