Article: How Old Plumbing Contributes to Bacteria in Water

If you live in an older home your water may be more likely to develop bacteria. While bacteria are invisible, the internal condition of aging pipes makes contamination far more likely. Understanding these risks helps you decide when to flush, replace fixtures, or test your water.

1. Corroding Pipes Release Particles That Feed Bacteria

Old metal pipes flake internally, releasing iron, rust, and sediment into the water. These particles work like fertilizers for microbial growth. Sediment settles in low-flow areas, creating pockets where bacteria thrive and multiply.

Corrosion also roughens the inside of pipes, giving bacteria more surface area to attach and build biofilm.

2. Biofilm Becomes Heavier in Older Plumbing

Biofilm forms in all plumbing, but older pipes accumulate more because:

• Minerals coat the interior
• Organic material sticks to rough surfaces
• Decades of water use create layered buildup

Once biofilm matures, it shields bacteria from disinfectants, allowing pathogens like coliforms and Pseudomonas to survive inside the plumbing system.

3. Temperature Instability Encourages Growth

Old water heaters, inconsistent insulation, and long plumbing runs often cause warm pockets within pipes. Bacteria multiply more quickly in warmer stagnant zones — especially when water flow is inconsistent.

4. Lead and Copper Plumbing Increases Contamination Complexity

Older homes may have: Lead pipes, Copper pipes with lead solder, Brass fixtures with high lead content.

When corrosion occurs, metals dissolve into water and interact with microbial communities. This can alter water chemistry, weaken chlorine residuals, and increase bacterial load.

5. Low-Use Lines Are Bacterial Hotspots

Spare bathrooms, basement sinks, and outdoor taps in older homes often go unused. Standing water loses disinfectant protection within days, allowing bacteria to grow unchecked.

6. Old Aerators, Showerheads, and Rubber Gaskets Trap Bacteria

Aerators easily accumulate:

• Rust
• Debris
• Biofilm
• Mineral deposits

This buildup shelters bacteria and reintroduces them into the water stream each time the tap is turned on.

7. How to Reduce Bacteria Risk in Old Plumbing

Flush Regularly

Run water in all taps weekly to prevent stagnation.

Clean Aerators

Remove screens and soak components in vinegar or a sanitizing solution.

Replace Rubber Components

Old washers, hoses, and gaskets can harbor mold and bacteria.

Flush the Water Heater

Older tanks accumulate sediment that must be removed.

Test the Water

Use an at-home bacteria test to screen for coliforms and E. coli, especially after flushing or plumbing work. An example test is Detekt Home's Total Drinking Water Test Kit.

Consider Partial Upgrades

You don’t need to replace the entire plumbing system — replacing the worst sections and key fixtures can significantly reduce contamination risk.

Old plumbing carries unique bacterial risks due to corrosion, sediment, biofilm, temperature shifts, and aging fixtures. By maintaining your system, cleaning key components, and testing regularly, you can ensure your water remains safe. 

By Ryan N., PhD