What is a copper sealing washer?

Copper sealing washers perform tightening functions in plumbing and heating applications that rely on copper tubing. As of 2015, about 95 percent of existing homes have copper plumbing, and despite the advent of newer materials, more than four out of five new homes have copper piping bringing the water supply.

Copper has remained a popular plumbing material because of its natural corrosion resistance, its relatively light weight, its durability without sagging in long runs and the leakproof joints that withstand wear and tear. Copper requires almost no maintenance, and just about every municipal and county plumbing code accepts copper for use in plumbing and gas distribution.