old water pipes corrosion water quality issues

How does old water pipes / corrosion impact water quality?

There are many myths about the dangers of water pipe corrosion and leeching to tap water quality. Some of them are simply urban legends and others are spread by water filtration companies to support the sales of their products. But there are also real dangers such as lead pipes and unknown risks of leaching plastic pipes. So what’s the truth about the dangers of old pipes to tap water?

In this article we address the most common ones and debunk the myths.

Common water pipe contamination myths

Let’s start with the most common myths about old pipes and water infrastructure.

  • Old corroding pipes in the city water network are the cause of bad taste, odor and contaminated water.
  • Old pipes are causing bacteria growth that can make me sick
  • Contaminants from water leaks are polluting the tap water making it unhealthy.
  • Plasticizers used in the manufacture of PVC pose a health issue

We will explain and debunk each of these below.

Where do tap water contaminants and other substances come from?

Tap water is never pure or perfectly clean. Normally it contains hundreds of substances in addition to H2O of which most are nothing to worry about.

There are essentially 5 sources of tap water contaminants/substances:

  1. The original source of the tap water which can be a river, lake, groundwater, aquifer or sea water (desalinated) – depending on the source my contain nitrates, bacteria, microplastics, pharmaceuticals and hundreds of other chemicals
  2. The water treatment plant / provider that treats the water with chemicals such as chlorine or chloramine and sometimes changes the properties of the water (softening, pH, sulphates, etc) – generally all regulated substances have been reduced to “safe” levels
  3. From the pipelines, pipes in homes, connections or faucet – e.g. lead, copper, zinc flakes)
  4. From local water tanks or pipes where the water sits for a long period of time which may cause bacteria growth
  5. From water filters that have not been changed on time (e.g. bacteria, contaminants that get released or filter elements that get released such as activated carbon)

In this article we will focus on (3) the pipes and what is known today about pipe contamination.

What are water pipes made of and what are the risks?

Most pipes from the water source to your faucet are made of galvanised iron/steel, copper, PVC (UPVC, CPVC) or PEX. Some old pipes before it was banned are made of lead which is generally considered the worst problem. Your water supplier is obliged to inform you if the network contains lead pipes.

Nearly all metals will corrode to some degree. The rate and extent of corrosion depends on the degree of dissimilarity of the metals and the physical and chemical characteristics of the media, metal, and environment. Let’s explore the issues and health hazards of each type of piping.

Iron cast pipes also known as galvanised steel pipes

Iron cast pipes will typically start rusting after a period of time and eventually the rust builds up and blocks the pipe. In the meantime the rust may collect in aerators and contaminate your tap water. There is no scientific evidence that this should cause health concerns.

Copper pipes

Corrosion of copper pipe can lead to levels of copper in the drinking water that exceed health guidelines and cause bitter or metallic tasting water. Water experts generally claim that it will be visible in terms of color of the water before it causes a health risk.


After 30+ years use there is limited evidence of PVC corrosion or leaching posing a health risk. However, preliminary findings show different PEX brands affect water quality at different levels, and even pipes that pass safety tests may contain enough contaminants to affect water’s taste and smell, Whelton says.

To date, more than 150 contaminants have been found in water that flowed through PEX pipes in these and other studies. Since each of the more than 70 brands of PEX pipes can leach different chemicals, and there are no enforceable federal regulations, it’s difficult for consumers to weigh the health risks.

Source: https://www.ewg.org/enviroblog/2017/11/amid-pipe-wars-researchers-wary-plastic-pipes-leaching-chemicals

Also, the rubber seals degrade after 25-30 years. Although this is more likely to cause a water leakage issue than a health risk.

Lead pipes

Lead is a real issue in the US and to some extent in Europe. Unfortunately Flint, Michigan and Newark, New Jersey are not isolated cases. In 2004, The Washington Post reported that 274 water utilities serving 11.5 million consumers had exceeded the Environmental Protection Agency’s lead standard in the previous four years and that several cities (including Boston, New York and Philadelphia) were out of compliance with EPA reporting requirements. Since then the replacement of lead pipes has accelerated but the problem has not gone away as we can see with recent cases.

The problem is that there is no safe level of lead for young children. In Washington DC in the 90s exposure was associated with a 37 percent increase in fetal deaths and hundreds of cases of elevated blood lead levels in young children. It’s also been found to cause an average 4 point decrease in IQ.

In Europe most public water infrastructure containing lead has been entirely replaced but old buildings, especially in the UK may still contain lead pipes.

Read more about how to remove lead from tap water .

Source: Washington Post Five Myths about lead in water

Bacteria growth in pipes

All types of pipes can experience bacteria growth although old dirty pipes are more at risk. Biofilm forms when biomass such as bacteria, fungi, algae and mold adhere to surfaces in wet environments. These may sometimes release into the tap water stream whereof most will be neutralised by the chlorine. Despite this, some bacteria will be found in all tap water even if it’s chlorinated. Fortunately this is very unlikely to pose any health risks based on 100 years of tap water research and studies. Water providers constantly monitor the risk of pathogens (bacteria and viruses) in the water network.

Read more about biofilm in bacteria and water pipelines and Good bacteria in tap water.

How can pipe corrosion be detected or identified?

There are basically 2 ways:

  1. Visual, taste or odor
  2. By testing the water quality

Let’s explore these in a bit more detail.

Identifying pipe corrosion and leaching through visual taste and odor

Water quality complaints that may be due to corrosion include:

Customer complaint Possible cause
Red water or reddish-brown staining of fixtures and laundry Corrosion of iron pipes or presence of natural iron in raw water
Bluish stains on fixtures Corrosion of copper lines
Black water Sulfide corrosion of copper or iron lines or precipitations of natural manganese
Foul taste and/or odors Byproducts from microbial activity
Loss of pressure Excessive scaling, tubercle (buildup from pitting corrosion), leak in system from pitting or other type of corrosion

Source: U.S. Environmental Protection Agency

Identifying pipe corrosion and leaching by testing the water quality

These are a couple of the key indicators:

  • pH: Water with a low pH (less than 6.0) tends to be more corrosive.
  • Turbidity: Pipe corrosion for iron and copper pipes can usually be detected by measuring water turbidity.
  • TDS: Higher Total Dissolved Solids and temperature than the source water also can indicate corrosivity.

The most used method is the Langelier Saturation Index is a means of evaluating water quality data to determine if the water has a tendency to form a chemical scale. In order to use this index, the following laboratory analysis is needed: pH, conductivity, total dissolved solids, alkalinity, and total hardness.

By calculating LSI it could be possible to predict and sense pipe corrosion before it becomes a serious issue.

Lead contamination still needs to be tested for specifically though. The best way of testing for lead is contacting a professional lab and asking them for a test kit.


In summary

  • Many issues of pipe corrosion and contamination that water filtration companies warn about are myths but there are real health issues such as lead and copper
  • Copper and Iron pipe corrosion is usually detected by visual signs and odor before it will do any harm
  • The risks of plastic pipes leaching are still unknown
  • A water filter with a high quality carbon block like EcoPro will protect you from potentially harmful substances from pipe corrosion including lead, iron, copper and leaching from plastic pipes
  • Lead in the tap water is a very serious issue as there is no safe level for young children or pregnant women
  • Bacteria can grow in pipes and this is why chlorine is added to tape water to keep it safe

Please contact us if you have comments or questions.

More reading about water pipe corrosion

How water providers manage pipe corrosion by controlling the pH:


Complete info on water pipe corrosion variables and causes:

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