PREVENTIVE MEASURES IN PLUMBING DESIGN FOR MICROORGANISMS
PREVENTIVE MEASURES IN PLUMBING DESIGN
Proper plumbing design is the first line of defense against the growth of microorganisms in a plumbing system. In general, in water with low or no disinfection, whenever an excessive quantity of water is stored and excessive surface area is available in the plumbing system, microorganisms can get the upper hand and form biofilms.
Plumbing designers should carefully plan the capacity of the water system. In modern plumbing systems, the high hot waterflow demands of large bathtubs and Jacuzzis control the plumbing system design. This leads to installation of large water softeners and hot water storage tanks which are oversized for typical water usage in the building when the tubs are not in use. This creates a long residence time for water inside the plumbing system.
Another area where biofilm development is typically found is in hot water recirculation systems. In larger residences and buildings, hot water is re-circulated between the faucets throughout the building and the storage tank in order to provide water at the desired elevated temperature immediately when a faucet is opened. The recirculation piping adds extra storage of water and residence time in the plumbing system and helps spread microorganisms from a location of biofilm development to other parts of the hot water system.
Water conservation devices also increase the time that water spends in the plumbing system.
Water treatment devices cause issues in that many remove disinfection from the water, provide a large volume of water storage, and provide greatly increased surface area on the treatment media, such as on physical filters, granular activated carbon, and softener resin.
Everyone involved in the design and construction of buildings should be aware that microorganisms can and do significantly affect water quality in plumbing systems and can even weaken the pipe itself. Modern plumbing systems with large bathtubs, increased use of water treatment devices, materials of construction that cannot come in contact with high disinfection concentrations, and water conservation devices contribute to the likelihood that microorganisms will grow in the plumbing system and form biofilms on pipe and tank surfaces.
Plumbing designers can do their part in preventing the growth of microorganisms and the development of biofilms by minimizing the residence time of water in the plumbing system and the surface area that the water contacts. Building con- tractors can do their part by routinely flushing the pipelines, disinfecting the water, and documenting disinfection concentration and microbiological activity.