August 31, 2020

How to Provide Safe and Sanitary DHW in 3 Basic Steps

As hot water flows throughout a building and returns in the recirculation piping, it cools. This can pose bacteria related health risks. The biorisks are magnified as the water cools below 120ºF or if the system is left idle for any length of time causing water stagnation.

These three steps will assist you in providing the ultimate goal:  delivering safe AND sanitary DHW.  

Step 1:  Digital Mixing

In a DHW system with no master mixing valve, it is common to set a storage tank temperature controller to 120ºF.   While this temperature is safe from the perspective of not causing scalding, it’s not hot enough to prevent the growth of Legionella bacteria.   Is there a suitable solution to control Legionella utilizing the existing system's infrastructure?


Step 2: Thermal Balancing

Thermal balancing valves excel at maintaining recirculation temperature at fixtures as demand conditions change by modulating flow in each riser circuit. The valves close tighter as riser temperatures increase and open as riser temperatures decrease.  Given the hot water delivered to the system during a thermal disinfection cycle which causes the valves to close to a minimum, how are the circuits flushed and disinfected sufficiently and automatically?  


Step 3: Scald Protection

The ultimate goal:  delivering safe tempered water at the point-of-use.   How are safe temperatures ensured at the fixtures during normal use and disinfection periods?



idronics™ is a complimentary educational journal series intended for plumbing and hydronic professionals to aid them in system design, component application and selection.   Enjoy these editions dedicated to the understanding of safe and sanitary DHW recirculation and delivery systems.

Please feel free to download technical content:


↓  GUIDE SPEC (rtf)

↓  idronics™ (Edition 21):  Recirulating Domestic Hot Water Systems

↓  idronics™ (Edition 22):  Safe and Sanitary Hot Water Delivery Systems

CALEFFI – Creating innovative, superior performance products that help customers live comfortably and economically,
while softening their impact on the environment.