In facilities that rely on steam boilers – whether in manufacturing, power generation, or commercial operations – the quality of water feeding the system isn’t just a technical concern. It’s a foundational element of operational success. Untreated or poorly treated boiler feed water is one of the leading causes of steam boiler inefficiency, corrosion, early system failure, and unnecessary downtime.

Proper boiler water treatment is no longer optional. It’s essential. And today, there’s a clearer standard guiding how it should be done.

What Are the ST-108 Guidelines?

Developed to standardize water treatment practices across industrial steam systems, the ST-108 guidelines establish clear performance expectations, chemical treatment benchmarks, and documentation protocols. These recommendations are helping facility managers shift from reactive maintenance to proactive system optimization.

Key ST-108 provisions include:

• Target ranges for dissolved oxygen, pH, and conductivity
• Guidelines for boiler blowdown control and frequency
• Clear expectations for oxygen scavenger application and internal treatment strategies
• Emphasis on documented monitoring and data logging to promote efficient operations
• Segmentation between feed water and condensate return zones

Together, they provide a framework for increasing boiler reliability, producing high quality steam, and lowering total cost of ownership.

For more on how EAI applies these principles, visit our Boiler Water Treatment Services.

What Is Boiler Water Treatment?

Water treatment of boiler systems is a multi-stage process that includes both external treatment (of the boiler feed water before the water enters the system) and internal treatment (within the boiler and steam cycle). The purpose is to remove or neutralize harmful impurities in feed water, makeup water, and condensate return before they cause scale, corrosion, or operational instability.

Typical treatment includes:

• Pre-treatment using softening, reverse osmosis, or filtration
• Chemical treatment such as oxygen scavengers, alkalinity builders, and scale inhibitors
• Continuous monitoring of parameters like conductivity, pH, and total dissolved solids (TDS)

Benefit #1: Preventing Scale Buildup and Heat Loss

Just 1/16 inch of scale buildup can reduce heat transfer efficiency by up to 15%. Over time, dissolved solids such as calcium carbonate, magnesium hydroxide, and sodium ions form deposits on boiler tubes, increasing thermal resistance and fuel consumption.

Proper boiler water treatment:

• Removes scaling minerals during pre-treatment
• Conditions residual hardness with synthetic polymers or soda ash
• Keeps dissolved solids within ST-108 conductivity targets

The result: consistent heat transfer, reduced fuel waste, and a lower risk of tube failure.

Benefit #2: Corrosion Prevention and Extended Equipment Life

Corrosion is primarily driven by dissolved oxygen and carbon dioxide in untreated water. These gases create acidic conditions that degrade metal surfaces, weaken welds, and trigger internal leaks – especially under high temperature and high pressure conditions.

Modern programs aligned with ST-108:

• Use oxygen scavengers like sodium sulfite or DEHA
• Maintain alkalinity with sodium hydroxide
• Stabilize condensate pH to prevent carbonic acid damage

With these controls in place, your boiler system not only runs longer – it runs safer.

Benefit #3: Lower Operating and Fuel Costs

Boiler water quality has a direct impact on fuel usage, maintenance budgets, and chemical efficiency. Even small deviations from optimal water chemistry can lead to outsized energy losses and mechanical wear in steam boilers and low pressure boilers.

Here’s how poor water treatment inflates operating costs:

• Scale buildup reduces heat transfer efficiency, requiring more energy to produce steam
• Corrosion shortens the life of tubes, valves, and pumps – leading to costly repairs or replacements
• Carryover introduces water and impurities into downstream equipment, reducing performance
• Inefficient blowdown wastes water, energy, and treatment chemicals

With proper treatment aligned to ST-108 recommendations, you can:

• Minimize boiler blowdown through tighter conductivity and TDS control
• Reduce excess chemical usage by maintaining target ranges
• Lower fuel consumption by keeping boiler tubes clean and conductive
• Prevent steam contamination that degrades equipment and forces unplanned downtime

Together, these improvements lead to smoother operation and a significant reduction in total cost of ownership. Over time, treatment programs that follow ST-108 not only protect systems – they pay for themselves.

Benefit #4: Compatibility with High-Pressure and High-Temperature Systems

High-pressure boilers – such as those used in chemical processing, power generation, or large-scale manufacturing – are more sensitive to fluctuations in water quality. With temperatures often exceeding 1,000°F and pressures above 600 psi, there’s little margin for error.

In these systems, even trace levels of dissolved gases, suspended solids, or volatile chemicals can result in:

• Catastrophic tube failure
• Excessive carryover into critical equipment
• Rapid degradation of downstream turbines, heat exchangers, and sterilization systems

ST-108 offers specific water quality targets for high-pressure applications, including:

• Dissolved oxygen limits under 0.007 mg/L
• Narrower alkalinity and conductivity ranges
• Enhanced data logging and automated monitoring

Proper external water treatment programs for these systems often include:

• Reverse osmosis or deionization for feed water purification
• Continuous chemical feed with precise pH and oxygen control
• Isolation of makeup water and condensate return to prevent cross-contamination

The right water chemistry doesn’t just protect high-pressure systems – it enables them to operate at peak efficiency for years.

Learn more in our guide to Water Treatment Strategies For Industrial Steam Boilers.

Benefit #5: Reduction in Boiler Carryover and Steam Contamination

Boiler carryover occurs when water droplets or dissolved impurities are carried into the steam system. This contamination can wreak havoc downstream, resulting in:

• Deposits inside steam lines, valves, and heat exchangers
• Reduced steam quality, impacting sensitive processes
• Damage to equipment like turbines, sterilizers, and reboilers
• Steam system fouling that leads to shutdowns or safety risks

ST-108 directly addresses this issue with:

• Recommendations for external treatment such as mechanical separators, drum level control, and baffles
• Tight TDS limits in high-pressure boilers
• Guidelines for antifoam agents, internal treatment adjustments, and blowdown control

A well-designed boiler water treatment program will:

• Maintain consistent steam purity across load conditions
• Limit the potential for foaming, priming, or water hammer
• Extend the life of expensive downstream assets

For more, visit our article on Boiler Carryover: What It Is and How to Prevent It.

Benefit #6: Improved Reliability of the Entire Steam System

A boiler doesn’t function in isolation – it powers an integrated network that includes feed water systems, steam traps, heat exchangers, and condensate return loops. When boiler water is improperly treated, the effects ripple across the entire system.

Common downstream consequences of poor water treatment include:

• Scaling and fouling in heat exchangers
• Sticky valves and failed steam traps
• Blocked or degraded condensate return lines
• Contaminant buildup in process equipment or sterilization units

By contrast, proper boiler water treatment:

• Maintains stable pH and conductivity, preventing mineral deposition
• Reduces corrosion products that can enter the condensate system
• Supports clean steam and pure vapor delivery to critical processes
• Ensures longevity and predictable performance from all system components

Following ST-108 guidelines helps facilities implement segmentation strategies – external treatment of feed water and condensate return systems independently when needed. This approach prevents cross-contamination and allows more precise chemical control in complex systems.

Ultimately, consistent boiler water quality translates into fewer service interruptions, lower repair costs, and smoother operations across the board.

Benefit #7: Support for Regulatory Compliance and Internal Standards

Boiler systems – especially in regulated industries like pharmaceuticals, food processing, and power generation – are subject to increasingly strict oversight. Agencies, auditors, and customers often require documentation proving that water quality is being actively managed.

ST-108 provides a foundation for achieving and demonstrating compliance, offering detailed guidance on:

• Documented operating limits for key parameters
• Required frequency of raw water and treated water testing (e.g., pH, dissolved oxygen, conductivity)
• Standardized practices for chemical feed adjustment
• Use of automated monitoring tools and data logging platforms

These practices don’t just make systems safer – they create defensible records that satisfy:

• Internal QA/QC protocols
• ISO, FDA, or HACCP audits
• Environmental reporting requirements
• Client contracts with performance clauses

Facilities that embrace ST-108-aligned water treatment programs can:

• Instantly provide treatment records and historical data
• Respond confidently to third-party assessments
• Identify and correct issues before they become violations

For facilities with lean operations or limited in-house expertise, partnering with a water treatment provider like EAI ensures compliance is not only achieved – but maintained with minimal friction.

For more detail, see our guide to Best Practices for Monitoring and Testing Boiler Water Quality.

Broader Impacts: Safety, Sustainability, and Long-Term Resilience

While water treatment delivers clear technical and financial benefits, its true value extends even further. From protecting your personnel to supporting sustainability goals and ensuring long-term system resilience, a well-executed treatment program strengthens every part of your operation.

In the final section, we’ll look at the last three benefits that tie it all together: how water treatment safeguards people, supports sustainability, and delivers long-term peace of mind.

Benefit #8: Enhanced Safety for Equipment and Personnel

Poor water quality isn’t just a maintenance issue – it’s a safety risk. Corrosion, scale buildup, and pressure instability can all contribute to dangerous operating conditions within the boiler and steam system.

Left unchecked, these risks may lead to:

• Boiler tube rupture due to thinning metal
• Over-pressurization from scaling-induced heat transfer loss
• Steam leaks and hazardous conditions for maintenance teams
• Unexpected shutdowns under full load

Proper boiler water treatment reduces these risks through:

• Use of oxygen scavengers and alkalinity builders to maintain safe chemistry
• Routine monitoring of pH, conductivity, and dissolved gases
• Stabilization of boiler feed water and condensate return chemistry to prevent corrosive conditions

ST-108 explicitly links water treatment to safety through recommendations on oxygen limits, blowdown practices, and system documentation. It reinforces the idea that safe operations are a function of both mechanical design and water chemistry control.

When treatment programs are properly implemented and monitored, systems operate more predictably – helping protect both equipment and the people who maintain it.

Benefit #9: Support for Sustainability and Reduced Environmental Impact

As industries place greater emphasis on sustainability, water treatment of boiler systems plays a key role in minimizing environmental impact. A well-managed boiler system consumes fewer resources and generates less waste.

Here’s how proper treatment supports sustainability:

• Reduced fuel consumption by maintaining clean heat transfer surfaces
• Lower chemical discharge due to optimized dosing and reduced blowdown
• Minimized water usage through efficient condensate recovery and tighter TDS control
• Less frequent replacement of corroded components, reducing manufacturing and shipping impact

ST-108 supports these outcomes by promoting data-driven treatment programs, which reduce overtreatment, unnecessary chemical use, and water loss. Facilities that follow these guidelines can achieve more than operational efficiency – they can align with corporate ESG goals and regulatory sustainability initiatives.

Benefit #10: Long-Term Operational Resilience and Peace of Mind

Finally, proper boiler water treatment provides something that’s often overlooked: stability. With volatile energy prices, supply chain delays, and tightening regulations, many facilities are searching for ways to insulate operations from uncertainty.

A properly treated boiler system is:

• More resilient to boiler feedwater quality fluctuations
• Less likely to suffer unexpected shutdowns
• Easier to manage with automated controls and predictive maintenance
• Aligned with ST-108, making it audit-ready and future-proof

In short, treatment isn’t just a technical fix – it’s a strategic advantage. It gives operators the peace of mind that their systems are running clean, safe, and stable, no matter what external pressures arise.

Turn Water Into a Strategic Asset

Whether you’re battling steam leaks, premature equipment failure, or rising energy costs, the underlying issue is often the same: untreated or poorly treated boiler water.

At EAI, we help facilities turn water from a liability into a long-term performance advantage – using programs that align with ST-108 guidelines, manage make up water quality, reduce operating risk, and improve ROI across the steam system.

If your boiler isn’t running clean, efficient, and compliant – it’s time to change that.

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