Why Filtration Alone Fails as an Infection Prevention Strategy in Building Water Systems

The Stream Analogy: Where the Water Is Cleanest

Imagine a clear mountain stream. At its source, the water is pristine, cold, fresh, and full of oxygen. But as that stream travels 100, 200, or 300 feet downstream, it picks up soil, debris, leaves, and microorganisms. The further it flows, the more it changes.

Now think of your facility’s plumbing the same way. It doesn’t matter how clean the water is when it enters the building if hundreds of feet of warm, stagnant pipes and biofilm-coated surfaces stand between the main and the faucet. New contaminants can be introduced all along the way.

A faucet filter at the end of that line is like putting a sieve at the very mouth of the stream. It can catch particles at that single point, but it does nothing to stop what’s happening upstream in the plumbing.

Why Filtration Is Not an Effective Long-Term Water Management Strategy

1. Filters Remove the Very Disinfectant That Keeps Pipes Safe

Municipal water arrives at your building with a disinfectant residual, typically free chlorine or chloramine. That residual is your first line of defense against microbial growth in the plumbing.

However, many point-of-use (POU) filters, especially those that rely on carbon adsorption or fine ultrafiltration, remove or neutralize that disinfectant. Once the residual is gone, bacteria and biofilm within the pipes are left unchecked.

As the EPA notes, “Disinfectant residuals in distribution systems help control biofilm and inactivate microorganisms. Removing that residual at a faucet can undercut the primary line of defense.”

In other words, the very filter intended to “protect” a patient or resident can actually remove the protection the entire system depends on.

2. Filters Do Not Treat or Penetrate Biofilm in Pipes

Legionella, Pseudomonas, and other opportunistic pathogens thrive in biofilms, thin layers of microorganisms attached to pipe walls. Biofilm provides nutrients and a protective barrier that shields bacteria from disinfectants and temperature changes.

Even the cleanest municipal water can become colonized once it encounters a biofilm-coated pipe. Filters cannot penetrate or treat these colonies. To manage risk effectively, you must treat the system, not just the water flowing through it.

Studies have repeatedly shown that building plumbing conditions such as temperature fluctuations, water stagnation, pipe materials, and residual decay determine whether Legionella grows or is suppressed.

3. Filters Require Intense Maintenance and Protect Only One Fixture

Even when POU filters are effective, their protection is limited to a single faucet or showerhead. They require precise installation, regular replacement, and ongoing monitoring.

In healthcare studies, filters have been shown to block Legionella for up to 12 weeks, but after that, effectiveness declines. A clogged or colonized filter can even become a secondary reservoir of bacteria, creating the very problem it was meant to prevent.

Filtration can play a short-term role in remediation, but it is not a sustainable infection prevention solution for complex plumbing systems.

What the Evidence Say

• Rising disease rates: Legionnaires’ disease cases have risen steadily in the U.S., reaching 9,933 confirmed cases in 2018, according to the CDC.

• Economic impact: Biofilm-associated pathogens such as Legionella, Pseudomonas, and nontuberculous mycobacteria account for the majority of hospitalizations and deaths from waterborne pathogens, costing over $2.3 billion annually in direct healthcare expenses (CDC, 2021).

• Filtration studies: Point-of-use filters can reduce Legionella presence for a few months, but multiple studies have shown they can also deplete disinfectant residuals and, in some cases, increase bacterial concentrations downstream when not properly maintained.

  
  

The conclusion from decades of research is clear: filtration alone is not enough.

The Real Solution: A Systems-Based Approach

True infection prevention requires a proactive, system-wide strategy that manages both water and the plumbing infrastructure.

According to the CDC and EPA, the most effective prevention methods include:

• Maintaining adequate disinfectant residuals throughout the building.

• Managing water temperatures and reducing stagnation points.

• Actively treating biofilm and pipe surfaces with effective chemical controls.

• Implementing a comprehensive Water Management Program (WMP) with monitoring, verification, and documentation.

  
  

This approach protects not just the faucet but every inch of pipe that delivers water to it.

Introducing WaterGuard MO

Filtration can be one layer of protection, but it should never stand alone. Legionella Specialties has developed a comprehensive solution designed to treat the plumbing system itself, not just the outlet.

WaterGuard MO is a mineral oxychloride-based treatment that supports a continuous disinfectant effect throughout premise plumbing. It works to:

• Help maintain a disinfectant residual in the system.

• Reduce the biofilm conditions that support Legionella and other pathogens.

• Work synergistically with flushing and temperature management programs.

  
  

When used as part of Legionella Specialties’ Treatment Program, WaterGuard MO becomes part of a complete, evidence-based water safety strategy combining treatment, testing, and management to help facilities meet compliance standards and reduce risk long term.

A Safer, More Sustainable Path Forward

Filtration can trap what is at the end of the pipe, but it takes active treatment to clean what is inside the pipe.

Protect your building, your patients, and your reputation with a water management strategy that addresses the real problem, the plumbing itself.