With many of the seasonal cooling towers offline for much of the winter, it is very important that they are cleaned before startup. Towers that have sat unused for months will inevitably house unwanted bacteriological growth. This happens because during the downtime, there is no biocide activity in the system. Even with the drains open, water can pool in a tower after a rain event and encourage the growth of bacteria.

The laws passed by New York State and New York City dictate that any tower that has been out of use for 5 or more days must be cleaned and disinfected before being placed back into service.