How To Reduce Cooling Tower Blowdown

Efficient water management is a critical aspect of cooling tower operation — especially for water cooled tower, blowdown water cooling tower, cold water basin cooling tower, and systems connected to a cooling tower chilled water system. Blowdown is the portion of water intentionally discharged from a cooling tower to control the concentration of dissolved solids and prevent scaling, corrosion, or biological growth in the circulating water loop. However, excessive cooling tower blowdown water increases costs, consumes resources, and can present environmental challenges.

In this article, we explain why blowdown happens, how to reduce it, and best practices you can implement — all while highlighting how Mach Cooling (https://www.machcooling.com/), a trusted cooling tower manufacturer, can support your optimized system design. 

 What Is Cooling Tower Blowdown and Why It Matters

Blowdown — sometimes called bleed-off — is water discharged from a cooling tower to control the level of dissolved minerals. When water evaporates (the primary cooling mechanism), the minerals remain and increase in concentration. Without blowdown, dissolved solids can reach damaging levels, leading to scale formation, corrosion, and system inefficiencies. 

 Typical Water Losses in Cooling Towers

Cooling towers lose water in four main ways:

Strong water management helps reduce unnecessary blowdown while keeping the system healthy. 

Strategies to Reduce Cooling Tower Blowdown

Reducing blowdown involves maintaining water quality so that the system can safely operate at higher concentrations of dissolved solids before needing to discharge water.

1. Increase Cycles of Concentration

Cycles of concentration (COC) measures how many times water circulates before being discharged relative to makeup water. Higher COC means lower blowdown volume. 

How to increase COC:

• Improve water treatment to control scaling and corrosion

• Use softening or pretreatment systems for makeup water

• Monitor conductivity and solids levels continuously

Example Target COC Table

By increasing cycles of concentration, water can be retained longer in the system, reducing cooling tower blowdown water discharged. 

2. Optimize Water Treatment Programs

A balanced chemical program protects surfaces and keeps dissolved solids under control. Excessive or insufficient chemicals can cause early blowdown due to scaling or corrosion concerns. 

Treatment tips:

• Use corrosion and scale inhibitors

• Maintain biological control to prevent algae and slime buildup

• Apply automated chemical feed systems to respond to real-time conditions

Proper treatment ensures your cold water basin cooling tower water remains in good condition at higher COC.

3. Conductivity-Based Blowdown Control

Installing sensors and automatic control valves that base blowdown on conductivity or total dissolved solids (TDS) prevents unnecessary water discharge. 

Benefit:
Instead of time-based blowdown, water is only discharged when needed to maintain your desired COC threshold — reducing wasted cooling tower blowdown water.

4. Side-Stream Filtration and Pretreatment

Filtering water removes suspended solids and reduces the rate at which dissolved solids accumulate, allowing longer intervals between blowdowns.

Common filtration methods:

• Side-stream filters

• Ultrafiltration

• Reverse osmosis (RO) pretreatment

Pretreated makeup water — especially via RO — has lower dissolved solids and increases system efficiency, meaning blowdown water cooling tower rates are significantly lowered. 

5. Reuse and Recover Blowdown Water

Instead of discharging blowdown directly to sewer systems:

Reuse options include:

• Irrigation and landscaping

• Dust control or cleaning water

• Makeup water after proper treatment

Treat and reuse blowdown to conserve water and lower operational costs. 

6. Improve System Efficiency

Improving airflow, heat transfer, and general operation of your water cooled tower reduces the amount of makeup water needed in the first place. Efficient systems produce less blowdown by minimizing unnecessary evaporation and heat load. 

Tools and Technologies That Support Blowdown Reduction

The right technologies can help your cooling tower chilled water system manage water more intelligently.

 Automated Sensors and Controls

Modern automation systems monitor:

• Conductivity

• Temperature

• Water level

…and automatically adjust blowdown rates to the minimal needed levels. 

Advanced Water Treatment Technologies

Tools such as:

• Reverse Osmosis systems

• Side-stream filtration

• Ion exchange softeners

improve makeup water quality and reduce total dissolved solids, enhancing overall efficiency. 

 Best Practices for Sustainable Blowdown Management

Managing blowdown sustainably requires attention to both operational practices and environmental considerations.

 Establish Clear Operating Targets

Define acceptable levels for dissolved solids, cycles of concentration, and blowdown frequency. Regular logging of these metrics helps you see trends and make adjustments before issues escalate.

Schedule Regular Maintenance

Routine inspection and maintenance help catch issues — such as failed float valves or sensor drift — that can cause unnecessary blowdown. 

 Track and Optimize Makeup Water Sources

Using alternative water sources for makeup reduces fresh water demand and total blowdown volume. This includes:

• Rainwater harvesting

• Greywater reuse

• Air handler condensate capture 

Why Partner with Mach Cooling

Mach Cooling (https://www.machcooling.com/) is a premier cooling tower manufacturer offering tailored solutions for water management in HVAC and industrial systems. Their expertise includes:

• Custom design of blowdown water cooling towers

• Integration with water treatment systems

• **Support for water cooled tower, cold water basin cooling tower, and cooling tower chilled water system applications

Working with experienced experts ensures that your system is optimized from design through operation — maximizing efficiency while minimizing water loss.

Summary: Practical Tips to Reduce Blowdown

Key Takeaways

• Maximize cycles of concentration to reduce blowdown water volumes. 

• Use smart blowdown control systems and sensors to discharge water only when needed. 

• Improve water quality and filtration to lower solids buildup. 

• Treat and reuse blowdown where feasible for sustainability.

• Partner with manufacturers like Mach Cooling for customized, efficient designs.

Reducing cooling tower blowdown not only conserves water but also cuts costs, improves equipment life, and supports sustainability goals.