Water Chemistry Parameters; Control Of Biological Contamination - EVAPCO ESW Series Operation And Maintenance Instruction

Water Chemistry Parameters

The water treatment program designed for evaporative cooling equipment must be compatible with the unit's materials of construction.
Control of corrosion and scale will be very difficult if the recirculating water chemistry is not consistently maintained within the ranges
noted in Table 4. In mixed metallurgy systems, the water treatment program should be designed to ensure protection of all the
components used in the cooling water loop.
Property
pH
pH During Passivation
Total Suspended Solids (ppm)*
Conductivity (Micro-mhos/cm) **
Alkalinity as CaCO3 (ppm)
Calcium Hardness CaCO3 (ppm)
Chlorides as Cl (ppm) ***
Silica (ppm)
Total Bacteria (cfu/ml)
* Based on standard EVAPAK
** Based on clean metal surfaces. Accumulations of dirt, deposits, or sludge will increase corrosion potential
*** Based on maximum coil fluid temperatures below 120°F (49°C)
If a chemical water treatment program is used, all chemicals selected must be compatible with the unit's materials of construction as well
as other equipment and piping used in the system. Chemicals should be fed through automatic feed equipment to a point which ensures
proper control and mixing prior to reaching the evaporative cooling equipment. Chemicals should never be batch fed directly into the
basin of the evaporative cooling equipment.
Evapco does not recommend the routine use of acid due to the destructive consequences of improper feeding; however, if acid is used
as part of the site specific treatment protocol, it should be pre-diluted prior to introduction into the cooling water and fed by automated
equipment to an area of the system which ensures adequate mixing. The location of the pH probe and acid feed line should be designed
in conjunction with the automated feedback control to ensure that proper pH levels are consistently maintained throughout the cooling
system. The automated system should be capable of storing and reporting operational data including pH reading and chemical feed
pump activity. Automated pH control systems require frequent calibration to ensure proper operation and to protect the unit from
increased corrosion potential.
The use of acids for cleaning should also be avoided. If acid cleaning is required, extreme caution must be exercised and only inhibited
acids recommended for use with the unit's materials of construction should be used. Any cleaning protocol, which includes the use of an
acid, shall include a written procedure for neutralizing and flushing the evaporative cooling system at the completion of the cleaning.
Flume/equalizer DO NOT ensure proper controlled mixing of water in multiple cells. Operate multiple cells individually.

Control of Biological Contamination

Building water systems receive potable and non-potable water from either a public or private entity for their water supply. This water
supply for the building water system can contain various waterborne pathogens, including Legionella bacteria, which can cause or
contribute to various illnesses if aspirated, ingested or inhaled. Since evaporative cooling equipment uses the same building water, there is
some potential that these pathogens, including Legionella, might propagate in the equipment. As such, evaporative cooling equipment
should be located at such a distance and wind direction to minimize the possibility of tower discharge air and associated drift being drawn
into building fresh air intakes or near areas frequented by at-risk individuals. Purchasers should obtain the services of a licensed
professional engineer or a registered architect to certify that the location of evaporative cooling equipment is in compliance with
applicable building, fire and clean air codes. (See EVAPCO's Equipment Layout Manual for more information.)
In addition, it is recommended that the building employ a site-specific water management program that is designed to minimize the risk
of Legionellosis associated with building water systems. (see ANSI/ASHRAE Standard 188-2018 for further details.) And effective water
management program also can help promote heat transfer efficiency and limit corrosion potential. Various water treatment professionals
are available to provide assistance with such measures.
G-235
Galvanized Steel
7.0 – 8.8
7.0 – 8.0
< 25
< 2,400
75 - 400
50 - 500
< 300
< 150
< 10,000
® fill
Table 4 – Recommended Water Chemistry Guidelines
Type 304
Stainless Steel
6.0 – 9.5
N/A
< 25
< 4,000
< 600
< 600
< 500
< 150
< 10,000
22
Type 316
Stainless Steel
6.0 – 9.5
N/A
< 25
< 5,000
< 600
< 600
< 2,000
< 150
< 10,000