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When Water Treatment Chemistry Changes, How Will Residential Piping Respond?

By: Jonathan Simon on October 9th, 2019

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When Water Treatment Chemistry Changes, How Will Residential Piping Respond?

Homebuilders  |  PEX  |  Water Quality  |  Copper  |  Water Chemistry

It’s natural to think of water as an inert, harmless liquid. But for the water running through municipal distribution systems, great care is taken, and extensive treatment is required to ensure clean, safe drinking water. The source water, whether it comes from a lake, river, reservoir or aquifer, inherently contains contaminants in the form of both dissolved solids and bacteria that requires treatment.  

As municipal water systems expand to reach new developments, treated water is traveling farther. Treatment processes must account for increased distances and water age in the system. In addition, new guidance on disinfection byproducts is leading some utilities to consider new treatment methods to ensure long-term water safety.

We know that water disinfection methods can cause corrosion and/or degradation in various piping materials like PEX and copper. With all of this potential for change in water treatment occurring today, how can builders ensure compatibility between their plumbing systems and the water flowing through them?

The Water Treatment Process

Ensuring compatibility starts with a basic understanding of municipal water treatment processes.

Municipal water treatment systems use a multi-stage treatment process that includes two stages of disinfection. The initial or primary stage is designed to kill the bacteria and germs that exist in the source water quickly. This is typically accomplished with chlorine; however, ozone or ultraviolet (UV) light are sometimes used.

Ozone and UV light have no residual effect on downstream water quality. Chlorine does have a residual effectiveness but breaks down fairly quickly. That’s why the secondary disinfectant stage is required. It ensures the water remains safe as it moves through the distribution system.

Chlorine, chloramine and chlorine dioxide can all be used as secondary disinfectants. Secondary disinfection levels must follow EPA guidelines for residual disinfectant throughout the system. Historically, chlorine was the disinfectant of choice for both primary and secondary disinfection, but recently municipalities have started to move from chlorine to chloramine or chlorine dioxide, both of which have a longer disinfectant life.

For a more detailed discussion of this topic, view our webinar.

Builders Bear the Burden

The regulations that govern water quality in the U.S. set minimum and maximum limits on the amount of disinfectant that can be in the water supply. In the process of ensuring clean safe drinking water, utilities frequently change their disinfectant levels or methods in response to changes in source water contamination, the expansion of the treatment facility to meet new demands, or regular maintenance of the water treatment equipment.


City of Tampa Water Quality ChangingThe City of Tampa recently notified residents of a temporary change in their water treatment process
through this notice on their website


When changes occur, water utilities may place a notification on their website or include a flyer in their billing statements; however, they are not generally required to do so. In most cases, these changes occur without anyone knowing or noticing – except for the occasional change in chlorine smell at the faucet.

We’ve written previously about the effect of chlorine on plastic piping materials, particularly PEX, noting that “chlorine attacks the molecular bonds in PEX piping, resulting in micro-cracks that gradually expand until the pipe fails.”

Moving to chlorine-based compounds that have a longer disinfectant life can result in more aggressive water conditions when water reaches its final destination, exacerbating inherent compatibility issues.

This appears to be the case in a well-publicized lawsuit in Southern California.  Homeowners filed a class action lawsuit against several municipalities in South County claiming the chloramine used in water treatment contributed to pinhole leaks in copper piping in a large number of homes.

The judge dismissed the suit because, even though the district changed its treatment process after the homes were built, it remained in compliance with state and federal standards related to water treatment. The standards don’t prevent the district from making changes that impact water chemistry as long as they remain within the limits.

While the municipality was found not liable, several builders agreed to settlements of more than a million dollars due to the damage caused by the leaking pipes.

It’s no surprise, then, that builders may feel like they are in an impossible situation. They are expected to ensure compatibility between piping materials and local water chemistry but have no control over changes to water chemistry after a home is built.

Ensuring Compatibility

Fortunately, this isn’t an impossible situation because there are some plumbing materials that are compatible with all water treatment practices and chemicals. As an inherently chlorinated polymer, FlowGuard Gold® CPVC is impervious to all forms of chlorine. FlowGuard Gold pipes and fittings will be compatible at installation and will remain compatible regardless of changes in municipal treatment processes.

Not only are FlowGuard Gold pipes and fittings resistant to chlorine, they help ensure superior water quality. FlowGuard Gold CPVC is virtually impermeable, doesn’t leach and has a lower biofilm formation potential than PEX piping. It is the only plumbing system on the market with a 30-year warranty that specifically applies regardless of the water treatment method.

While you can’t control water treatment practices, you can control your choice of plumbing material. Make the switch to FlowGuard Gold CPVC today.


water conditions webinar