These guidelines are available for download.
Fire Hydrant Flow Test Guidelines
In general, the waters that are discharged during fire hydrant flow testing have little potential to contain pollutants. The primary exception is chlorine, which is a common constituent of municipal waters. However, fire hydrant flow testing generates large quantities of water with high velocity flows. Uncontrolled, these flows can create erosions and contribute sediment to receiving water bodies. In addition, these flows pick up other pollutants from the surfaces over which they travel and wash them to the receiving waters.
When chlorinated municipal waters are the source of water for the discharge and the discharge will travel less than 1,000 feet before entering a river, stream or other receiving water, the discharge shall be aerated and/or treated in such a way that the chlorine level is reduced or dissipated prior to discharging to the receiving waters by using sodium thiosulfate or another de-chlorination method. If necessary, the water to be discharged can be directed through hay bales, over grassy areas or rip rap and/or otherwise sufficiently aerated, bypassing several storm sewer inlets as necessary to dissipate the chlorine prior to discharging to the receiving water body. A pool chlorination kit can be used to confirm that there are no detectable levels of chlorine in the water prior to discharge.