Hercules Megaloc Thread Sealant from Oatey is a multipurpose sealant with a nonseparating, nonflammable, and nonhazardous odorless formula. Able to withstand temperatures ranging from -50°F to 400°F without hardening or cracking, the sealant can be used on steel, stainless steel, brass, copper, aluminum, and plastics, and is safe for use on drinking-water lines, according to the manufacturer. A 4-fluid-ounce container costs about $8.50. oatey.com