An important advantage that developed countries have is good infrastructure — a reliable electrical grid, decent transportation network and properly maintained water and sewer systems. Imagine your doctor having to wake up at 5 a.m. to look for firewood and water before going to his or her practice. How good could that doctor be?
Unfortunately, over the years investment in these crucial infrastructures has woefully declined to the detriment of many communities, particularly in rural and less affluent areas. Many communities no longer have the finances to maintain their dilapidated water and sewer systems, thereby exposing and subjecting residents to incessantly lower-quality water and service.
Building owners and operators must provide a safe and healthy environment for users and occupants. That duty surely extends to the quality and safety of water within a buildings domestic water system. Recently, the quality of potable water, the plights of poor communities and the declining state of infrastructure have been brought to the forefront by events such as the Flint, Mich., water crisis and numerous outbreaks of Legionellosis.
Such an unfortunate crisis can provide important lessons pertinent to water distribution systems in buildings: Water distribution systems are susceptible to chemical and microbial contaminants; Water distribution systems in buildings can act to amplify and disseminate waterborne microbes and chemical contaminants; The quality of potable water entering a building is not always as it should be and, therefore, should not be taken for granted; There is an urgent need for better plumbing design to at least ameliorate and at best prevent the occurrence of contaminants within potable water systems in buildings; and Some building occupants/users are more susceptible to contaminants than others; therefore, the water system should be designed to protect the most vulnerable.
Of late, plumbing design has mostly focused on reducing cost and increasing water efficiency, sometimes at the expense of safety associated with potable water. Many times, systems and equipment made to safeguard the quality of potable have been value-engineered out of a project to save money.
In some cases, implementation of low-flow equipment has increased the residence time of potable water or outright stagnation. These, in turn, has resulted in degradation of the quality of potable water. Some studies have linked low-flow faucets and rubber materials found within them with increased colonization of Legionella bacteria.
To ensure the health and safety of occupants and users, proper design, installation and operation of a potable water system are paramount. The following points can help safeguard domestic water distribution systems.
Prevent contaminants from entering
the potable water system
Contaminants can be introduced in the potable water system during construction — with incoming potable water or during equipment servicing. During construction, potable water pipe should be kept clean and stored in a segregated, secure location away from construction dirt and debris. Before installation, the pipe segments should be inspected for cleanliness and blasted with air to remove any loose dirt.
After installation, the piping system should be disinfected in accordance with protocols outlined by the authority having jurisdiction. Based on my experience, disinfecting potable water piping is best done by an independent, experienced water treatment professional as part of building commissioning, as opposed to the mechanical contractor.
The first line of defense for protecting the potable water system from possible contaminants in the incoming water is to install a filtration skid on the incoming water line.
Skid components should include an appropriately sized particulate filter (preferably 20 -50 microns) to remove suspended solids. The particulate filter should have a differential pressure gauge or other means to monitor and indicate when the filter media needs to be backwashed or replaced. Cartridge or bag filters with replaceable cartridges/bags are better-suited for potable water because mixing of clean and dirty water can be avoided entirely. Also, backwashing filters require the wastewater line to drain, thereby risking wastewater backflow and or reverse colonization due to backsplash.
Components should also include a chemical filter such as a carbon block/activated carbon media may be used to remove organic and heavy-metal contaminants from incoming water. In addition, a microbial disinfectant/sanitizer such as ultraviolet light or ozone to prevent waterborne germs should be included— including chlorine-resistant Giardia and Cryptosporidium — from entering the potable water.
Prevent proliferation of contaminants within building water systems The second line of defense is to provide systemic water treatment to prevent the proliferation of contaminants in the building water system. Systemic water treatment processes that can provide measurable residual treatment include, but are not limited to, chlorination, chloramination, chlorine dioxide or copper-silver ionization.
Water recirculation circuits such as hot water loops that are vulnerable to the occurrence of Legionella bacteria warrant extra attention. Protection can be improved when a systemic water treatment is coupled with a particulate filter installed on a recirculating loop. The filter will act to remove suspended solids continuously, thereby reducing demand for disinfectant.
Different treatment options offer unique advantages and disadvantages. The best protection is attained when two systemic water treatment options are used alternatively or concurrently. However, their compatibility must be considered.
Design with cleanliness in mind
Our views and designs of water distribution systems in buildings are antiquated. Piping systems are designed inaccessibly — out of sight, out of mind. If you keep using the same cup to drink clean water, at some point, you will be drinking dirty water.
Water is the primordial home of life and no matter how clean it is at the beginning, without periodic “shock treatment,” its conveyance system will be contaminated. Buildings and different sections of buildings should be designed with dedicated bypass/recirculation/disinfection loops. This will allow the piping system of a building section to be isolated and disinfected more easily and regularly, not just when there is an occurrence of an outbreak.
The right choice of piping material and components
Piping material and components have an important and direct impact on the quality of potable water. Some piping materials are more susceptible to microbial biofilm colonization than others. Piping material may also limit the kind and amount of residual disinfectant that can be used. Carbon steel pipe and components should be eschewed in potable water systems because they are highly prone to corrosion and oxidation by residual disinfectants.
By now it should be blindingly obvious that no components containing any amount of lead should be permitted in potable water. Extra precautions should be taken, especially when potable water is being supplied for nonpotable water uses such as cooling tower makeup, greywater tanks, water features and irrigation systems. Regular inspection of backflow preventers and anti-siphon apparatus ensures they are still functioning as required.
Seek advice from water treatment experts and qualified technicians Mechanical contractors and even current water treatment personnel may not be qualified to deal with potable water. Water in a nonresidential building is considered more or less public. If this water will be treated for use by the public, perhaps the building operator needs to be a certified public water operator.
At times, issues about potable water are serious and sometimes are a matter of life or death. A plumbing designer should not be hesitant to seek outside help, especially when working on projects involving health facilities such as hospitals and elderly-care homes where the primary population is more predisposed to potable water contaminants.
Implement hygienic operating protocols at the earliest opportunity Operating potable water systems to effectively maintain safety and hygiene require more than standard operating procedures and equipment manuals.
For instance, if filters will be used to filter municipal water at the point of entry, will the operator be required to disinfect filter media, vessel or other equipment/tools associated with potable water system before, during and after every servicing? How will this be carried out? Will replacement filter cartridges be required to meet NSF 61 standards or cheaper, noncompliant ones be allowed because of budget constraints?
Institute continuous water quality surveillance
Water distribution systems are important disseminators of waterborne contaminants — biological and chemical. Moreover, water infrastructure has been subject to hacking by nefarious states. Continuous surveillance of building water distribution systems can serve an early warning in detecting such activities and safeguarding the health and safety of users.
Continuous surveillance encompasses:
• Monitoring water quality and quantity from entry to exit of the building — pH, disinfectant level, hardness, TSS, pressure, temperature, flow rate and daily consumption, among others.
• Monitoring the quality of processed water for various uses within the building.
• Keeping in constant communication with water-source owners and operators in municipalities.
• Awareness of what is happening in and around the building that can adversely affect water quality — such as nearby construction activities, flooding and fires — and reacting to them in a timely and effective manner.
• Having a response plan in case of an event, such as a boil water notice, microbial contamination or cross-contamination among other incidences.
An incident with a client revealed other advantages of continuous surveillance. A water treatment system served by potable water was faulting out due to high-temperature alarms. The faults almost exclusively occurred when the building was unoccupied — at night and over the weekends. When the building operator reset the equipment, no faults occurred throughout the day.
A major source of the alarm was an incidental high temperature of influent potable water — above 80 F and occasionally above 96 F, whereas at the faucets, the water temperature was consistently around 56 F. Replacement of temperature sensors in the equipment did not solve the problem and the client was frustrated. Theories and speculations abound to explain the faults, including the existence of ghosts. A team member even jokingly suggested getting a priest for an exorcism.
Before embarking on removing the insulation and cutting into the influent water line to install a continuous temperature monitor, the operator decided to trace influent water supply all the way to the take-off point in the mechanical room. To his surprise, the potable water line to an electronic mixing valve was warm to the touch. Further investigation revealed a hot water check valve was malfunctioning and letting hot water backflow into the cold-water supply line.
But this malfunction only happened when potable water flow was very low, which coincided perfectly with low building occupancy. Were it not for the high-temperature alarms on the water treatment equipment, this malfunction would have never been detected, perhaps until the conditions would have been worse. Warm temperatures between 77 F and 108 F in the potable water system promotes the growth of Legionella bacteria; therefore, it is important to keep cold water cold and hot water hot.
The current state of our water infrastructure has revealed many vulnerabilities in potable water systems in buildings. To ensure the health and safety of occupants and users, proper design, installation and operation of a potable water system are paramount.
Plumbing designers can play an important role in ameliorating or preventing the occurrence of waterborne microbe and chemical contaminants in building water distribution systems.