May 11, 2020

Safe and Sanitary Plumbing for Commercial Buildings

How to reopen after COVID-19.



The COVID-19 pandemic is causing commercial buildings such as day care facilities, hotels, schools and health clubs to remain closed for abnormally long periods. When the coast is clear to begin reopening, ensuring safe and sanitary plumbing water will be of utmost importance.  Plumbing systems left idle can be susceptible to harmful bacteria such as Legionella which can proliferate to dangerous concentrations.

Experienced water maintenance managers know susceptible systems should be flushed before reusing. Important considerations should not be overlooked such as ensuring all service lines are purged and dead legs drained.

Several factors determine if the system equipment requires treatment such as how long a system is left idle, the temperature of the stagnated water and condition of the internal surfaces. This is so bacteria that are resistant to simple purging/draining and have become resident in biofilm can be addressed. Common methods include thermal treatment or treating with chemicals such as chlorine, chlorinated gas and chlorine dioxide.

A significant benefit of thermal treatment is that it’s a proven, cost-effective method for bacteria management on an ongoing basis in the hot side of the plumbing system. The cold side doesn’t typically require ongoing treatment unless water remains stagnated for extended periods within the temperature range that Legionella grows which is 68°F to 122°F.    

Thermal treatment requires little additional maintenance compared to chemical treatment. Also, common plumbing equipment such as seals, gaskets and polymer components are not exposed to potentially incompatible life-shortening chemicals. Residual chemicals in the water can also be a human health concern if acceptable concentration values are exceeded. In contrast, most common plumbing materials can withstand, without effect, thermal shock temperatures such as 160°F.

Thermal treatment consists of periodically circulating elevated water temperature such as 160°F through the entire system for a specific and measured period of time, thereby killing harmful bacteria and restoring the water to a safe and usable condition. During this period it is important to ensure all point-of-use fixtures are either disabled for access or equipped with anti-scald devices.  An example is the Caleffi scald-protection valve SinkMixer™ - an innovative, easy to install valve for under-sink applications.

Often the most difficult portions of the hot water side to circulate sufficiently through is the recirculation return risers. This because they are sized and balanced to a relatively low flow rate such as 0.5 GPM. The Caleffi ThermoSetter™ thermal balancing valve automatically responds when it senses high temperature water by fully opening an internal by-pass, thereby allowing a sufficient return riser flushing during treatment. It then automatically returns to standard operation state when water temperature decreases to normal.  

If a building is equipped with a Caleffi LEGIOMIX® digital mixing valve, it will enjoy highly accurate mixed water temperature 24/7. The LEGIOMIX has industry-unique, calendar-based automatic thermal disinfection programs. For thermal monitoring, it has data logging capabilities and can connect to a building automation system for remote monitoring and access.

LEGIOMIX combined with SinkMixer anti-scald valves and ThermoSetter recirculation balancing valves offer an innovative total thermal solution for control of safe and sanitary domestic hot water.

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

while softening their impact on the environment.