A common mistake homeowners make when doing DIY repairs is connecting pipes that are different metals, such as steel and copper. When two different metals are joined, dielectric corrosion can occur. This will eventually build up in your pipes and cause a blockage. In order to prevent this from happening, plumbers use a special dielectric union. The union separates the two metals with a rubber washer and plastic sleeve so they do not touch, thus preventing corrosion.
If you have questions about any plumbing issues, call Covenant Plumbing - your trusted local plumbing resource.