A well-maintained hydronic heating system provides reliable performance even during the harshest winters. Heating maintenance professionals know that top quality materials are critical to achieve superior performance. That's why contractors depend on our stop-leak products. They are formulated for high performance and developed with both the user and the environment in mind. "Clean and friendly" furnace cement is the latest example of this commitment. It's patented formula is the first and only to meet OSHA's requirement of less than .1% crystalline silica.