Why Is Cooling Tower Conductivity Too High? Troubleshooting Guide Malaysia
# Why Is Cooling Tower Conductivity Too High? Troubleshooting Guide Malaysia
High cooling tower conductivity is a common water-treatment and maintenance concern.
A conductivity reading that is higher than normal does not automatically mean the conductivity meter is faulty, nor does it immediately identify a specific chemical problem.
Instead, high conductivity generally indicates that the concentration of dissolved ionic substances in the water has increased.
For cooling tower maintenance teams, the key question is:
Why has the conductivity increased?
Possible causes include evaporation, insufficient blowdown, changes in make-up water, chemical treatment, operating load or measurement problems.
A systematic troubleshooting approach can help identify the cause.
## What Does Cooling Tower Conductivity Mean?
Electrical conductivity (EC) measures the ability of water to conduct electrical current.
Dissolved ions contribute to conductivity.
These can come from:
- Minerals
- Salts
- Acids
- Alkalis
- Water-treatment chemicals
- Other dissolved ionic substances
Conductivity is commonly expressed as:
**µS/cm**
or:
**mS/cm**
depending on the measurement range.
For cooling towers, conductivity is particularly useful because evaporation concentrates dissolved substances.
## Why Does Conductivity Normally Increase in a Cooling Tower?
Cooling towers reject heat partly through evaporation.
When water evaporates:
**Water leaves the system**
but:
**Most dissolved minerals remain**
The remaining circulating water therefore becomes progressively more concentrated.
A simplified sequence is:
**Make-Up Water → Circulation → Evaporation → Concentration**
As ionic concentration increases, conductivity generally increases.
Therefore, cooling tower water will commonly have higher conductivity than the make-up water.
The question is whether the increase is consistent with the water-treatment program.
## Cause 1: Insufficient Blowdown
Blowdown removes a portion of concentrated cooling tower water.
Fresh make-up water replaces it.
If blowdown is insufficient, dissolved substances may continue accumulating.
The result can be:
**Increasing concentration → Increasing conductivity**
Check:
- Blowdown valve operation
- Automatic blowdown controller
- Conductivity set point
- Water flow
- Solenoid valve operation
- Manual valve position
If the system uses automatic conductivity control, verify the online reading using a portable conductivity meter.
## Cause 2: Blowdown Valve Is Not Opening
An automatic controller may request blowdown while the valve itself fails to operate correctly.
Possible issues include:
- Solenoid failure
- Blockage
- Wiring problem
- Mechanical valve problem
- Closed isolation valve
Do not assume the control system is functioning simply because the display appears normal.
Compare actual system operation with the controller status.
## Cause 3: Online Conductivity Sensor Is Dirty
Cooling tower sensors can accumulate:
- Scale
- Slime
- Biological growth
- Chemical deposits
- Dirt
A fouled sensor may provide incorrect or unstable readings.
Use a calibrated portable EC meter to compare:
**Online EC reading**
versus:
**Portable EC reading**
A large difference should trigger investigation of the sensor, sampling method and calibration.
## Cause 4: Portable Conductivity Meter Is Not Calibrated
The portable instrument itself can also be wrong.
Before changing the cooling tower operation, check:
1. Probe cleanliness
2. Calibration
3. Conductivity standard
4. Temperature compensation
5. Measurement range
Never adjust blowdown based on one questionable measurement.
## Cause 5: Make-Up Water Conductivity Has Increased
Cooling tower conductivity is affected by the quality of incoming make-up water.
If the make-up water EC changes from:
**300 µS/cm**
to:
**500 µS/cm**
the circulating-water conductivity may also increase even if the cooling tower operation has not changed significantly.
This is why maintenance teams should measure both:
**Make-Up Water EC**
and:
**Cooling Tower EC**
rather than looking only at the tower.
## Cause 6: Higher Evaporation Rate
Hot weather or increased cooling load can increase evaporation.
More evaporation can concentrate dissolved substances more quickly.
Possible situations include:
- Hot weather
- Higher production load
- Increased chiller load
- Higher building cooling demand
- Changes in cooling tower operation
This makes trend monitoring important.
A conductivity number should always be interpreted in operational context.
## Cause 7: Chemical Dosing Changes
Cooling-water treatment chemicals can contribute dissolved ionic substances.
A change in chemical dosing may therefore affect conductivity.
If conductivity rises unexpectedly, review:
- Recent chemical dosing
- Chemical pump operation
- Treatment concentration
- Maintenance work
- Changes made by the water-treatment contractor
Conductivity cannot identify the exact chemical involved, but it can indicate that the overall ionic condition has changed.
## Cause 8: Water Loss or Make-Up Problem
If normal make-up water flow is reduced while evaporation continues, circulating water may become more concentrated.
Check:
- Make-up valve
- Float valve
- Water level control
- Water supply
- Make-up meter
- Basin level
The problem may therefore be mechanical rather than chemical.
## Cause 9: Conductivity Controller Set Point
Automatic blowdown systems may use conductivity as the control parameter.
If the set point has been changed, the system may intentionally operate at a different conductivity.
When troubleshooting, verify:
**Current set point**
against:
**Approved water-treatment set point**
Do not assume the controller setting has remained unchanged.
## Cause 10: Sampling Error
Sometimes the cooling tower is
20 Aug 2026
