Issue link: https://hi.iaq.net/i/692160
DEVELOPING A LEGIONELLA WATER MANAGEMENT PROGRAM 9 2 4. Hot water is distributed to plumbing fixtures in the basement through floor 5 from the joined water heaters in the basement on a direct (non-recirculating) line. Hot water is distributed to floors 6 through 11 from the storage tank with a recirculating line designed to return to the joined water heaters in the basement. Note that hot water is tempered (mixed with cold water) at the fixtures by thermostatic mixing valves. Note: Water in direct hot and cold water pipes can pose multiple hazardous conditions. First, the process of heating the water can reduce disinfectant levels. Second, if hot water is allowed to sit in the pipes (stagnation), it might reach a temperature where Legionella can grow and could encourage sediment to accumulate or biofilm to form. With recirculating hot water pipes, the greatest risk is that returning water with reduced or no disinfectant cools to a temperature where Legionella can grow. If this happens, Legionella in the return line can travel to central distribution points and contaminate the entire plumbing system of the building. 5. Hot, cold, and tempered waste water is discarded through the sanitary sewer line. Note: It is not known at this time if Legionella can grow and spread in sources such as harvested rainwater or reclaimed graywater (i.e., bath, laundry). Reference: ASHRAE 188: Legionellosis: Risk Management for Building Water Systems June 26, 2015. ASHRAE: Atlanta. www.ashrae.org Disclaimer: Example content is provided for illustrative purposes only and is not intended to be relevant to all buildings.