What It Is
Pipe corrosion is the chemical or electrochemical degradation of pipe material from contact with water, oxygen, minerals, or dissimilar metals. It reduces pipe wall thickness, creates interior buildup that restricts water flow, and eventually produces pinhole leaks or complete pipe failure. The rate of corrosion depends on pipe material, water chemistry, water temperature, and pH level.
What It Does
Corrosion affects pipes from two directions. On the outside, moisture in soil or concrete can attack buried or embedded pipes, causing exterior pitting. On the inside, water chemistry is the primary driver. Water that is acidic (low pH) aggressively dissolves copper and galvanized metal. High chlorine content, common in municipal water, accelerates corrosion in copper and some alloys. Hard water deposits scale but also creates conditions where pitting corrosion can begin under the deposits.
Galvanic corrosion is a specific type that occurs when two dissimilar metals are in contact in the presence of water - for example, copper pipe connected directly to galvanized steel without a dielectric union. The less noble metal (galvanized) corrodes much faster than it would alone.
How It Works
In the most common form, iron-based pipes (galvanized steel, cast iron) oxidize when water and oxygen are present, forming iron oxide (rust). This rust flakes off, staining water reddish-brown, and leaves the pipe wall thinner. Copper forms a greenish patina (cupric oxide) on its exterior but generally resists corrosion better than steel. In acidic water, copper can corrode from the inside and leave blue-green staining at fixtures.
Northeast Ohio's hard water is high in calcium and magnesium but not particularly acidic, meaning scale buildup is more common than aggressive metal dissolution. However, older galvanized pipes in the region are often severely restricted by decades of rust and scale accumulation.
Common Problems or Signs of Failure
- Rusty or reddish-brown water, especially when first running a tap after a period of no use
- Blue or green staining at faucets or drain openings - copper corrosion byproduct
- Pinhole leaks appearing in copper pipes - aggressive water chemistry or age
- Reduced water pressure in specific sections - interior scaling from corrosion deposits
- Visible exterior rust or pitting on exposed pipe sections
- Flaking or deteriorating pipe surfaces when touched
Can a Homeowner Check It?
- Inspect exposed pipe sections in the basement or utility room for rust, pitting, or green patina
- Run cold water for 30 seconds and collect a glass - check for discoloration or particles
- Look at water stains in the toilet bowl and sink - orange-brown indicates iron; blue-green indicates copper
- Identify pipe materials in your home (galvanized, copper, PEX, PVC) - age and material together predict corrosion risk
When to Call a Plumber
Call a plumber if you find pinhole leaks, notice consistently discolored water, or have galvanized pipes that are more than 40 years old. A plumber can inspect exposed sections, run a camera through drain lines, and advise on targeted repairs or full repiping. Catching corrosion early - before a pipe section fails inside a wall - avoids much more extensive water damage repairs.
Related Plumbing Problems
- Why Is My Hot Water Rusty or Discolored?
- Why Is My Water Pressure Low?
- Do I Have a Hidden Water Leak?
- Why Is My Water Bill High?
Related Plumbing Terms
Related Gray's Services
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