Chairman Education Committee
One Member’s Opinion
Water piping for HVAC
Water piping serving HVAC projects (hot water and chilled water) is a “closed system”, where the water filled at the beginning, is continuously re-circulated. Make-up water, in small quantities, is added to compensate water lost due to leakage of the system. The water is maintained at temperatures of 180-200°F, for hot water which kills bacteria and 40-45°F for chilled water, which do not allow bacteria to multiply. Special chemicals (bactericides) can be added to the system to keep bacteria from multiplication or kill them.
Another system is the water from the cooling tower, (condensing water), is an exception. This water system is an “open system” because condensing water becomes in contact with outside air and will add more bacteria and viruses, when the cooling tower water runs thru the cooling tower.
A recent article published in Water Conditioning and Purification of September 2017 prepared by Timothy Keister CWT, FAIC, entitled “Using Softened Water for Cooling Towers” makes the argument for the benefits of using soft water for Cooling Towers.(Very interesting article with diagrams and calculations to justify his proposal)
Potable water piping.
Potable water piping serving Plumbing projects is an “open system”, where every time a faucet is open for flushing a Lavatory, WC, Sink, Urinal, etc., a fresh quantity of municipal water is admitted into the system. This fresh water admits in the Plumbing systems: Salts, impurities and bacteria allowable in the municipal potable water systems, based upon archaic EPA definition.
Therefore, the proposed procedures to prevent growth of bacteria for HVAC projects must be different than the procedures for Plumbing projects.
Some bacteria produce a “biofilm”, which will deposit inside the pipes, and will protect other bacteria covered by “biofilm” from being destroyed by biocides or temporary super hot water (160°F) circulated occasionally.
The way I see it, the water entering the building from municipal piping should be free of any bacteria, viruses or microbes and to have minimal residual salts, minerals or other chemical compounds. For instance: minerals, as calcium carbonate (CO3Ca) or magnesium carbonate (CO3Mg), will eventually deposits inside the pipes and equipment, will produce a scale, which will increase the friction loss (more energy to move the water), will corrode the pipe and will be an excellent place for bacterial development. Various USA zones contain water with high concentration of these compounds (hard water). Removing them from water entering the building will save a lot on energy and maintenance. This is beneficial for Plumbing and HVAC systems.
Attached Fig. 1, Fig.2 and Fig.3 show proposed equipment to be installed where municipal water piping enters the building. This equipment will improve the water quality distributed in the building.
Plumbing water piping disinfection.
Pipes and materials used for potable water piping systems shall be certified to comply with NSF (National Sanitation Foundation) Standard 61.
Piping shall be delivered at site with caps on all open ends and stored to prevent contamination with foreign particles as sand, dust, rust, etc.
At the end of each working day, all open pipe ends shall be capped to prevent contamination.
A thorough flushing and disinfection of plumbing piping system, in accordance with AWWA C 651 or as required by Code, with chlorine or other bactericides, and final flushing must be performed before plumbing piping is accepted to be used by the occupants.
After disinfection, samples of water shall be collected and submitted to a Certified Lab to determine the concentration of bacteria. If bacteria are detected, the procedure shall be repeated.
Also, water entering the building from municipal piping, should have a device, for instance a UV (Ultra Violet) generator, to destroy all bacteria and viruses for potable water, supplied to the building occupants.
Potable water systems designed and installed based upon traditional practices include uncounted number of “dead ends”, serving plumbing fixtures, water hammer arrestors, flushometer valves, equipment, etc. Bacteria once admitted in the Plumbing Systems will be very difficult, if not impossible, to destroy them.
A recent study performed in a hospital in Sherbrooke, Canada determined that heat exchangers, installed to conserve energy, promoted growth of Legionella in the hot water supply. The study appeared in the Journal of the Society for Healthcare Epidemiology of America. The conclusion was: Remove heat exchangers. Reason: “No energy or water savings are worth a human life”
Water Management Plan (WMP)
ANSI/ASHRAE Standard 188-2015 requires that all buildings, except single family, shall have a WMP.
We should differentiate WMP for existing buildings from WMP for new buildings.
Existing buildings plumbing systems were designed and installed with no special attention to WMP.
New buildings plumbing systems should be designed and installed to comply with new rules to restrict or limit exponential multiplication of bacteria or other pathogens in plumbing systems. Building Owners and Managers, as responsible parties, should have a plumbing system which can be monitored and disinfected, if necessary. This can be accomplished by proper design.
Smart loop hot water recirculation system.
Recently I read about a relatively new system for recirculation of hot water for large buildings, called “smart loop system”, offered by Viega, as part of pro press piping system. The system includes hot water recirculation pipe (HWR), inside hot water (HW), and a special “double drop elbow”, which eliminates “dead ends” for supplying water to fixtures.
Fundamental criteria to combat micro organisms in potable water piping.
Prevention is preferable to cure.
Micro organisms have an extraordinary fast way to multiply, and mutate to be resistant to antibiotics or other medications we invent.
Remove or destroy any micro organisms, before potable water enters building piping distribution systems.
Remove salts and minerals from water supplied from municipal pipes.
Some of these minerals will eventually precipitate and deposit inside pipes and equipment, and will be an excellent place for micro organisms to hide and multiply. This can be accomplished by using water softeners or other procedures.
Best Available Technology (BAT)
The fight against Legionella just started. Appears that bacteria are a step ahead of our technology to destroy them, and protect our population. Therefore, in the near future, we should expect more outbreaks of Legionella disease. In the mean time we should adjust and continue our fight, by using revised and improved BAT.
RULES AND REGULATIONS TO LIMIT LEGIONELLA DEVELOPMENT.
There are several documents we should be aware of, regarding monitoring, inspections, testing and recording the changes of water systems in the buildings. At this time I am aware of following documents:
ANSI/ASHRAE Standard 188-2015
Water Management Plan (WMP)
Center for the Disease Control (CDC) tool kit
Center for Medicare Services (CMS), June 02, 2017
Inspecting Hospitals and Nursing Homes for Legionella requirements. In the event that activity of Legionella is found, will be necessary some disinfection or other procedures applied to water systems. None of documents listed above, provide any specific procedures for remediation. This part of activity is left to each facility.
I can’t imagine the level of confusion, when each, facility will potentially use a different way solve the problem. I agree that for ”old” buildings, already in operation, the remediation will be specific for each building to accommodate piping and controls available.But for new buildings we have to design piping distribution systems, to facilitate the remediation. This is what I propose in this article. This is a proposal, based upon my limited knowledge of equipment and technologies available.
I am asking everyone interested, to send me, his/hers suggestions and comments.
Request for review and comments. I prepared this document, based upon my limited knowledge of all equipment and devices available to combat multiplication of micro organisms in potable water systems.
It is agreed by all authorities, that micro organisms and chemicals in potable water systems are detrimental to health and safety of population. As professionals, we should use all existing and new technologies, to prevent spreading diseases and allowing deposits of scale on pipes and equipment of potable water systems.
All these suggestions, really will require a new approach for designing these water systems . We should not expect that a Plumbing Engineer/Designer alone will come up with a proper design of improved systems.
This complex task, calls for collaborative effort of many engineers, contractors, and manufacturers. ASPE is the organization which should take the lead.
Please call or write to me with your comments and suggestions.