Why Is Boiler Water Conductivity or TDS Too High? Malaysia
# Why Is Boiler Water Conductivity or TDS Too High? Malaysia
High boiler water conductivity or TDS is a common issue encountered by boiler operators, facility maintenance teams and industrial water-treatment personnel.
In many boiler systems, conductivity increases because dissolved ionic substances remain behind as water is converted into steam.
However, if conductivity or TDS rises significantly above the normal operating trend, technicians should investigate the cause rather than immediately assuming that the meter—or the boiler—is faulty.
Possible causes include:
**Insufficient Blowdown → Higher Feed-Water Conductivity → Chemical Dosing Changes → Increased Boiler Load → Water-Treatment Problems → Sampling or Instrument Error**
A systematic approach can help determine what has changed.
## What Does High Boiler Conductivity Mean?
Electrical conductivity measures how easily water conducts electrical current.
Dissolved ions increase conductivity.
These ions can originate from:
- Minerals
- Salts
- Water-treatment chemicals
- Acids
- Alkalis
- Process contamination
- Incoming make-up water
Conductivity is normally displayed as:
**µS/cm**
or:
**mS/cm**
A higher reading generally indicates a higher concentration of dissolved ionic substances.
However, conductivity does not identify exactly which substances are present.
## Why Does Boiler Water Become Concentrated?
A boiler converts water into steam.
A simplified process is:
**Feed Water → Boiler → Steam**
Many dissolved substances do not leave with the steam.
They remain behind in the boiler water.
As more steam is generated:
**Water leaves → Dissolved substances remain → Concentration increases**
This is one reason boiler water normally requires controlled blowdown.
## What Is Boiler Water TDS?
TDS means:
**Total Dissolved Solids**
Many portable TDS meters do not directly measure the mass of dissolved solids.
Instead, they measure conductivity and calculate an estimated TDS value using a conversion factor.
Therefore:
**Higher EC → Usually Higher Displayed TDS**
but:
**EC ≠ TDS**
The TDS conversion factor should be considered when comparing instruments.
## Cause 1: Insufficient Boiler Blowdown
One of the first areas to investigate is blowdown.
Blowdown removes concentrated boiler water.
If insufficient water is removed while steam generation continues, dissolved substances may become increasingly concentrated.
This can produce:
**Rising Conductivity + Rising TDS**
Check:
- Blowdown frequency
- Blowdown duration
- Automatic blowdown operation
- Valve condition
- Controller setting
- Approved boiler-water treatment procedure
Do not randomly increase blowdown without considering the treatment program.
## Cause 2: Automatic Blowdown Controller Problem
Some boiler systems use conductivity to control blowdown automatically.
If the controller or associated equipment is not operating correctly, boiler-water conductivity may rise.
Possible problems include:
- Conductivity sensor fouling
- Incorrect controller set point
- Calibration error
- Solenoid valve failure
- Wiring problem
- Blocked blowdown line
- Isolation valve position
A portable conductivity meter can provide an independent verification reading.
## Cause 3: Conductivity Sensor Is Dirty
Online conductivity sensors operate continuously in industrial environments.
Deposits can affect measurement.
Possible contamination includes:
- Scale
- Treatment chemical residue
- Dirt
- Process contamination
If the online meter suddenly reports unusual conductivity, compare it with a properly calibrated portable instrument.
Check:
**Online Conductivity**
versus:
**Portable Conductivity**
A significant difference should be investigated.
## Cause 4: Feed-Water Conductivity Has Increased
Do not troubleshoot boiler water without checking feed water.
If feed-water conductivity increases, boiler-water conductivity may also increase.
Compare:
**Make-Up Water EC**
↓
**Treated Water EC**
↓
**Feed Water EC**
↓
**Boiler Water EC**
This can help identify where the change begins.
## Cause 5: Water-Treatment System Problem
A change in feed-water treatment can affect boiler-water chemistry.
Depending on the plant, investigate equipment such as:
- Water softener
- RO system
- Demineralization system
- Chemical dosing system
- Feed-water treatment equipment
If treated-water conductivity has changed significantly, the problem may originate before the boiler.
## Cause 6: RO Performance Has Changed
Some boiler plants use reverse osmosis as part of feed-water preparation.
Conductivity is particularly useful for checking RO performance.
Compare:
**RO Feed EC**
with:
**RO Product EC**
If product-water conductivity rises unexpectedly, the RO system may require investigation.
The issue could then appear later as increased boiler feed-water conductivity.
## Cause 7: Chemical Dosing Has Changed
Boiler-treatment chemicals can contribute ionic substances.
Changes in chemical dosing can therefore affect conductivity.
Check:
- Dosing pump operation
- Chemical concentration
- Recent treatment adjustments
- Chemical tank changes
- Water-treatment contractor records
Conductivity alone cannot tell you which chemical caused the increase.
It tells you that ionic conditions have changed.
## Cause 8: Boiler Load Has Increased
Higher steam demand can change operating conditions.
If steam production increases significantly, water concentration behaviour and blowdown requirements may also change.
Compare the high conductivity reading with:
- Steam load
- Production level
- Feed-water consumption
- Blowdown operation
Water-quality data is more useful when interpreted together with operating data.
## Cause 9: Feed-Water Flow Changes
Changes in feed-water supply can influence boiler-water concentration.
Check:
- Feed-water pump
- Water level
- Control valve
- Feed-water flow
- Make-up water conditions
A mechanical issue can sometimes appear first as a water-quality trend.
## Cause 10: Sampling
20 Aug 2026
