25 May 2005
Week (for example, 1/W = once per week).
Day (for example, 1/D = once per day).
Slowly soluble polyphosphate chemicals used in treatment of small
and medium cooling towers should be checked at least weekly and
replaced as necessary.
Frequency of Cooling Water Sampling and Testing. Water samples of
the recirculating water in small towers (less than 88 kilowatts [25 tons]) be sampled and
tested at least once per week, those of medium-sized towers (88 to 352 kilowatts [25 to
100 tons]) at least 2 times per week, and those of large towers (more than 352 kilowatts
[100 tons]) daily. You can establish a routine schedule that is designed to meet these
goals for sampling and testing. For many cooling towers, the makeup water quality is
quite consistent over time. Collection and analysis of 1 sample per week of the makeup
source is usually an adequate frequency. If makeup water quality varies, increase the
frequency to allow for sampling of makeup water at the same time as cooling water
sampling. Always flush the water sample line prior to sampling.
Cooling Water Sampling. Cooling tower water samples are collected in
clean, 1-liter (1-quart) glass or plastic bottles. The bottle is capped (sealed) immediately
and tested without delay (i.e., within 1 hour since some water quality will gradually
change). The sample is not collected immediately after the addition of treatment
chemicals but is collected after the chemicals have been allowed to mix thoroughly with
the system water. Samples of the recirculating cooling water can be collected by dipping
from the cold well, or can be collected from the recirculating pump discharge after the
line has been flushed for 10 seconds or until no sediment remains. If these locations are
inaccessible, another location may be used. Typical sampling points for an open
recirculating system are shown in Figure 6-1. It is best to always collect the sample for
each system in the same manner and from the same location for consistent results.