What happens when different materials are joined in a water piping system?

• A. Increased deterioration of the pipe
• B. No effect
• C. Improved flow
• D. Increased stiffness

Answer: (A)

When different metals are joined in a water piping system, a galvanic reaction can occur. Water with minerals acts as an electrolyte, and the two metals form a tiny battery at the joint. The more anodic metal corrodes faster while the more cathodic metal is relatively protected, leading to accelerated deterioration at the joint and along the pipe over time.

That’s why mixing dissimilar metals often results in leaks or weakened fittings, rather than any improvement in flow or strength. To prevent this, plumbers use dielectric unions or keep the same material throughout, or otherwise isolate the metals with nonconductive barriers.