Maintenance and Water Quality

Effective maintenance and water quality management are essential for evaporative cooling system performance, efficiency, and longevity. Proper care prevents scale buildup, biological growth, and premature equipment failure while maintaining design cooling capacity.

Water Quality Fundamentals

Source Water Characteristics

Incoming water quality affects system operation:

Concentration Effects

Evaporation concentrates dissolved minerals:

$$TDS_{sump} = TDS_{makeup} \times Cycles$$

Where cycles of concentration typically range 3-5.

Example: 300 ppm makeup water at 4 cycles = 1,200 ppm sump concentration

Scale Prevention

Scale Formation

Calcium carbonate (CaCite) precipitation occurs when:

$$[Ca^{2+}][CO_3^{2-}] > K_{sp}$$

Factors promoting scale:

• High temperature
• High pH
• High hardness
• Low bleed rate

Bleed-Off Control

Continuous bleed maintains acceptable concentration:

$$Bleed\ Rate = \frac{Evaporation\ Rate}{Cycles - 1}$$

Example: 10 GPM evaporation, 4 cycles target $$Bleed = \frac{10}{4-1} = 3.3\ GPM$$

Chemical Treatment

Scale inhibitors prevent mineral precipitation:

Treatment Types:

• Polyphosphates: Sequester hardness
• Phosphonates: Crystal modification
• Polymers: Dispersant action

Consult water treatment specialist for specific recommendations.

Water Softening

Softening makeup water removes hardness:

• Ion exchange (sodium exchange)
• Reduces calcium and magnesium
• May increase sodium/TDS
• Extends media life significantly

Biological Control

Microbial Growth Concerns

Warm, wet conditions promote biological growth:

Common Organisms:

• Algae (green/brown discoloration)
• Bacteria (biofilm, slime)
• Fungi and mold

Health Concerns:

• Legionella pneumophila
• Other opportunistic pathogens

Legionella Prevention

ASHRAE Guideline 12 addresses Legionella risk:

Risk Factors:

• Water temperature 77-113°F (optimal 95-115°F)
• Stagnant water
• Scale and sediment accumulation
• Inadequate biocide treatment

Prevention Measures:

1. Maintain biocide program
2. Regular cleaning and disinfection
3. Eliminate stagnant water
4. Control scale and sediment
5. Monitor water quality

Biocide Treatment

Chemical biocides control microbial growth:

Consult water treatment specialist and follow manufacturer guidelines.

Media Maintenance

Rigid Media (Cellulose)

Inspection Schedule:

• Weekly: Visual inspection for damage, algae
• Monthly: Check distribution uniformity
• Seasonal: Deep inspection, pressure wash if needed

Cleaning Procedures:

1. Shut down system
2. Drain sump completely
3. Remove loose debris
4. Flush with clean water
5. Apply biocide treatment
6. Allow media to dry if storing

Replacement Indicators:

• Efficiency drop >10%
• Physical degradation
• Persistent odor
• Scale accumulation unremovable

Typical Life: 5-10 years with proper maintenance

Aspen Pads

More frequent replacement required:

• Inspect monthly
• Replace 1-3 seasons typical
• Check for compression, thinning
• Easy replacement (slide in/out)

System Components

Water Distribution

Maintenance Items:

• Clear clogged nozzles/orifices
• Check trough level and overflow
• Verify uniform distribution
• Clean strainers and filters

Sump and Pump

Routine Maintenance:

• Remove sediment accumulation
• Check float valve operation
• Verify pump flow rate
• Inspect pump strainer
• Check for leaks

Seasonal Tasks:

• Drain and clean sump
• Inspect pump impeller
• Check electrical connections
• Verify motor operation

Air-Side Components

Fan and Motor:

• Lubricate bearings (if applicable)
• Check belt tension and condition
• Clean fan blades
• Verify motor amperage

Air Intake:

• Clean intake screens
• Check damper operation
• Remove debris accumulation

Seasonal Procedures

Start-Up (Spring)

1. Inspect media for damage
2. Clean sump thoroughly
3. Check pump operation
4. Verify water distribution
5. Test controls and safeties
6. Establish water treatment program
7. Verify airflow and temperature drop

Shutdown (Fall)

1. Drain all water from system
2. Clean sump and media
3. Treat media with biocide
4. Cover or seal unit
5. Disconnect power
6. Document condition

Winter Freeze Protection

If operating in cold weather:

• Drain water when idle
• Heat trace critical components
• Insulate exposed piping
• Install freeze protection controls

Maintenance Schedule Summary

Documentation

Maintenance Records

Track:

• Water quality test results
• Treatment chemical usage
• Media condition and replacement
• Component repairs
• Operating hours

Water Management Plan

ASHRAE Standard 188 may require documented plan:

• System description
• Risk assessment
• Control measures
• Monitoring procedures
• Corrective actions

Diligent maintenance and water quality management maximize evaporative cooler performance, extend equipment life, and ensure safe, healthy operation throughout the cooling season.