Compression fittings are very common materials in plumbing. This is popular with Do-It-Yourselfers as a safe way to join copper pipe without the use of heat.
Compression fittings are necessary connectors to make different types of valves, tees, connectors and utilities watertight and safe. The new fitting will have a similar depth so the pipe will go into a depth where the existing olive will seal.
How compression fitting work
It works by the compression of an ‘olive’ within two tapered surfaces and the pipe itself. The two surfaces are the body of the fitting (be it a valve, connector or any other type) and the nut. Using a spanner and a pair of grips the nut is tightened. This exerts pressure on the olive and bites it onto the pipe.
Clean and properly-cut pipes will make the compression fittings work well. Using a pipe slice is a good tool for such a job and are excellent in tight spaces.
Cut and clean the pipe. Then put together the compression fitting by sliding on the nut and olive at both ends. Use a grip to hold the compression fitting body tightly and tighten the nut with a spanner.
Do not over tighten a compression fitting to leave you with more thread in the event of a leak and not crushing the olive or fitting. Commonly, a nut will need one whole turn after hand tightening. Also, for a better watertight seal, you want to wrap PTFE tape around a compression fitting olive.
Can plumbing olives be reused? The answer is no. Olives can't be used once removed from the pipe. Even hand tightening a fitting with olive inside before the pipe is enough to make the olive unusable.