Free Engineering Tool

Thermal, Chemical & pH Intersection Matrix

Visualize your facility's theoretical risk of Legionella pneumophila amplification. This model demonstrates the biological efficacy of your control strategies aligned withASHRAE 188and ASSE 12080 principles.

Tool Preferences
6.5 (High Efficacy / Corrosive)7.5 (Neutral)8.5 (Low Efficacy / Scaling)
Active Chlorine (HOCl)
~68%
Theoretical Legionella Risk vs. Control MeasuresDiminishing ReturnsHigh Corrosion & CostNegligible Biological BenefitDanger ZonePeak GrowthOptimal HotOptimal Cold510152025303540455055606570Water Temperature (ºC)0.00.51.01.52.02.53.0Free Chlorine Residual (mg/L)Risk020406080100

The Danger Zone (77ºF - 113ºF / 25ºC - 45ºC)

Legionella amplification is optimal here. Low chlorine (< 0.5 mg/L) is rapidly consumed by biofilm, offering zero protection. You must rely on heavily elevated chlorine, which is difficult to maintain deep in premise plumbing.

Diminishing Returns (High Heat + High Cl)

Temperatures > 131ºF (55ºC) are highly effective at killing Legionella alone. Injecting high free chlorine (> 1.0 mg/L) at these temperatures provides virtually no biological benefit. Heat rapidly destroys the chlorine residual, while aggressively corroding copper and PEX.

Optimal Zones (Cold & Hot)

Cold: < 68ºF (20ºC). Bacteria are dormant. Standard municipal chlorine residuals (0.2 - 0.5 mg/L) are stable and sufficient.

Hot: Circulating at > 124ºF (51ºC) (hitting 140ºF/60ºC for complete thermal eradication). Thermal control dominates. Trace chlorine is helpful but not the primary defense.

Stop Guessing. Start Controlling.

Now that you know your ideal control limits, let us generate the paperwork. Build a complete, audit-ready ASHRAE 188 Water Management Plan tailored to your specific building topology.

  • Auto-populated ASSE 12080 limits
  • Custom process flow diagrams
  • Joint Commission ready

Free WMP Generator

No credit card required. Build your plan anonymously and only sign up when you're ready to download.

Launch WMP Wizard