Pipe joint compound, also known as pipe dope, is a type of sealant used with any type of threaded pipe to help create a seal. Consisting of a mixture of substances, including kaolin, clay, vegetable oil, rosin and ethanol, pipe-joint compound serves as both a lubricant and a sealant for threaded joints. Using pipe joint compound on the threads of a pipe joint helps to ensure a water- and air-tight seal.
Any plumbing project involving the use of threaded pipe requires the use of a sealant in the form of involving the use of threaded pipe requires the use of a sealant in the form of the pipe-joint compound, plumber's tape (Teflon tape) or a combination of both.
Where to Buy Pipe-Joint Compound
Pipe-joint compound is available in a tube or in a canister with a brush applicator. The manufacturer's specifications are an important consideration when purchasing a sealant for your particular project. It is important to note if the product is intended for use on only one certain type of pipe, or if it is a universal product that can be used on both metal and plastic. When buying pipe-joint compound, look for a product that can be used on all types of plastic and metal threaded pipe, and keep it on hand as part of your collection of basic plumbing tools and materials.
How to Use Pipe-Joint Compound
To use pipe-joint compound, simply apply an even coating onto the end of a threaded pipe, using either the applicator brush or a finger.
Then, thread the pipe into the fitting, making sure to avoid cross threading that might damage the threads. Many plumbers use a thin layer of pipe-joint compound on top of plumber's tape for a great seal on almost any threaded joints involving water.
NOTE: One important thing to keep in mind is that some types of sealants are not appropriate for both water and gas.
Plumber's tape, for example, comes in two types—one for use specifically on gas, and one for water pipe. This can also be true for a pipe-joint compound, so read the product usage specifications carefully.