How to Clean and Treat a Closed Loop Hydronic System in Commercial Buildings
Posted by David Cannon on 5th Jun 2025
Why You Should Maintain Your Closed Loop Hydronic System
A closed loop hydronic system is the heart of many commercial HVAC systems, especially those designed for heating hot water circulation. While these systems are designed to be low-maintenance, they are not immune to internal corrosion, sludge buildup, and system inefficiency.
Over time, dissolved oxygen, leftover oils and flux, or existing corrosion by-products can circulate through the system, causing:
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Decreased energy efficiency
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Pump and valve failure
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Costly system repairs or replacement
To keep your system operating at peak performance, regular cleaning and chemical treatment are essential.
Step 1: Clean Your System with an Eco-Friendly HVAC Cleaner
Before adding any HVAC corrosion inhibitor, it’s critical to clean the system thoroughly. This step removes:
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Iron oxide (rust)
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Organic and biological buildup
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Pipe dope, solder flux, and installation oils
We recommend EcoGreen PreClean, a non-hazardous, biodegradable cleaning solution ideal for commercial closed loop HVAC systems.
Dosage: 12 oz to 1 gallon per 100 gallons of system water (for heavily fouled systems)
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To validate the cleaning process, use our Cleaner Test Kit to monitor the chemical levels during circulation.
Get the Cleaner Test Kit
Step 2: Apply a Corrosion Inhibitor for Long-Term Protection
After cleaning and flushing the system with clean water, the next step is corrosion protection.
CS400P is a nitrite-based closed loop system corrosion inhibitor specifically designed for commercial HVAC systems. It protects:
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Iron and steel
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Brass, bronze, and copper
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Aluminum components
Coverage: 1 gallon per 500 gallons of system fluid
P/N: CS400P-5 (5-Gallon Pail)
Price: $122.50
Order CS400P Corrosion Inhibitor
For ongoing water treatment monitoring, use a Nitrite Test Kit to verify the correct inhibitor concentration.
Shop the Nitrite Test Kit
Step 3 (Optional): Improve Water Quality with a Filter Feeder
If your closed loop HVAC system has been neglected or if particulates continue to circulate after cleaning, we highly recommend installing a side-stream filter feeder.
Benefits of a Filter Feeder:
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Captures suspended solids and iron oxides
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Reduces fouling in heat exchangers and coils
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Provides a safe and easy method to inject corrosion inhibitors
We recommend the Vector FA-900AL, a 7-gallon filter feeder with a 25-micron sock filter.
View the Vector FA-900AL Filter Feeder
Commercial HVAC Water Treatment You Can Trust
Routine water treatment is the key to a long-lasting, high-efficiency commercial closed loop HVAC system. By following this three-step approach:
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Clean with EcoGreen PreClean
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Treat with CS400P corrosion inhibitor
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Filter particulates with a Vector FA-900AL filter feeder
You’ll reduce costly downtime, improve energy efficiency, and extend equipment life.
If you’re responsible for building maintenance or HVAC water treatment, Cannon Water Technology has the products and expertise to help.
Need Help? Contact Us Today!
Whether you need a complete water treatment plan or help choosing the right chemicals, our expert team is just a call or email away.