Closed Loop Water Treatment

Closed Loop Water Treatment Services

Typical heating or cooling systems include three types of loops: a chilled water loop, a refrigerant gas loop and a cooling tower water loop. These types of closed loop systems are susceptible to leaks that can lead to contamination-forming corrosion and bacteria in the cooling water that may ultimately cause a total system failure.

Chardon Laboratories can provide effective chemical treatment for closed loop systems that can prevent leakage and other troublesome issues from occurring. Our ISO-certified technicians can perform a wide range of services that will keep your closed loop water cooling system operating at peak efficiency, while also minimizing the risk of extensive damage.

Our Closed Loop System Treatment Services Include:

  • A Free Survey to determine the current system status and needs
  • Prevention of corrosion, scale and other microbiological growth
  • Cleaning & Flushing
  • Corrosion Coupons
  • Regularly scheduled testing a treatment through a customized chemical treatment plan
  • Continued maintenance at a steady and consistent annual price
  • All treatments administered by ISO-certified technicians to ensure system longevity

Read on to find out all we can do for you!

technicians can perform services to keep your closed loop system operating at peak efficiency

This includes minor preventive maintenance steps such as changing filters, pH and conductivity testing as well as complete cleaning and flushing, replacement equipment and much more.

Closed Loop System Cleaning & Flushing Procedure

Our proven technique for cleaning and flushing closed loop systems is a highly effective solution for preventing microbiologically influenced corrosion (MIC), a leading cause of closed loop leakage. MIC occurs when bacteria colonizes and begins to feed on the system’s iron surfaces.

We implement a three-step cleaning and flushing process consisting of a non-acid chemical cleaning, a thorough flushing to remove iron deposits and the application of a biocide to sterilize the system and kill any remaining bacteria. This provides an extremely effective defense against the formation of MIC.

Other Methods for Preventing Corrosion in Closed Loop Water Systems

Chardon Labs implements a number of effective techniques for preventing corrosion. We work with the dissolved solids within the system,to render the water less aggressive, and thus, less corrosive. We accomplish this by utilizing the various proprietary chemicals to treat the water.

We also eliminate corrosion by maintaining the optimal pH level in the loop water within the noncorrosive range. This can be achieved by adjusting the pH with various chemicals. Controlling the pH will also help with problems associated with iron.

In closed looped systems that have no exposure to air, the best way to minimize the risk of corrosion is removing oxygen from the water. This will slow the spread of corrosion on metal surfaces. The implementation of the proper water treatment chemicals removes oxygen, thereby reducing the risk of corrosion.

Another method we employ for preventing corrosion is the use of compounds that form protective films on closed loop system surfaces. These chemicals will protect and passivate metallic surfaces.

Loop Treatment Professionals

large closed-loop tank and tube systems

Your closed loop system is just as susceptible to malfunction as any open system. Undiagnosed leaks permit air to enter the system, allowing for corrosion and bacteria to begin contaminating the cooling water.

diagram of the pump, filter chemicals, and heat exchanger in a closed-loop system


How Chardon Helps

Filters must be changed regularly, and pH and conductivity must be tested to prevent corrosion and deterioration of components to allow for adequate heat transfer efficiency. Your closed loop may be corroding from the inside out and you might not even know it. A proper flush and regular testing of the loop water is required to ensure the longevity of the entire system.

Contact Us today to request a free evaluation of your closed loop system and find out the potential savings you could missing out on.

“We don’t sell chemicals, we sell clean systems.”




Chardon Labs is a NSF Certified Water Treatment

Cleaning and Flushing Procedure for Closed Loops

If It’s A Closed Loop, Why Does It Need To Be Flushed?

In theory, water should never leak out of a closed loop.  While there are closed loop systems that rarely lose water, most closed systems lose a small amount of water during the course of normal operation.  This typically happens when pump seals leak or molds are changed.  Unfortunately, most closed loop system designs do not account for this lost water by automatically adding closed loop treatment as make-up water is added to the loop. The make-up water not only dilutes the corrosion inhibitor and reduces its effectiveness, but also adds oxygen which can promote corrosion on many surfaces.

What Happens To Corrosion By-Products In A Closed Loop?

The corrosion inhibitor treatment level decreases in the loop as make-up water is added to replace leakage. Corrosion by-products tend to accumulate in closed loops since the water recirculates without blow down. Iron is the most common corrosion by-product in closed loops. Even though some iron is lost through leakage, the reduced treatment level rapidly exceeds the ability of the leak to control the amount of iron dissolved in the water. As the concentration of iron increases, the solubility is exceeded, and precipitation occurs. This results in iron deposits.

iron is the most common corrosion by-product in closed loops


What is Microbiologically Influenced Corrosion?

Often referred to as MIC, Microbiologically Influenced Corrosion occurs when one or more species of bacteria colonize and begin feeding on the iron surfaces in a system. Colonies can attack all types of ferrous metals including iron, mild steel, galvanized and stainless steel. The metabolic process of Sulfate-Reducing Bacteria (SRB) uses the conversion of iron to iron oxide to create energy.

Galionella also converts iron to iron oxide. Clostridium excretes hydrogen ions which react with water to form strong organic acids. The common result in pits in the surface of the metal that are hidden under tubercles of iron oxide.

How Can I Clean Microbiologically Influenced Corrosion Up?

Removing the iron deposits involves a non-acid chemical cleaning, a thorough flushing of the system to remove the iron, and a biocide to sterilize the system.  Here are the steps:

  • If the water in the loop is already heavily fouled or dark in color, begin by flushing at a rate of 1-2 gallons per minute from a valve at a low point in the system. It is important to monitor the pressure on the circulating pump during this stage. If the flushing rate exceeds the make-up rate, the system volume will drop and the pump will cavitate. This can cause expensive damage to the pump bearings and impellor. By making sure the pressure is maintained in the system, you ensure that the pump will not run dry. Continue flushing until the water consistently runs clear. Depending on the volume in the loop, this may take as long as 5-7 days. Count on approximately 12 hours of flushing for every 1,000 gallon in the loop.
  • Once the water is clear, add the chemical loop treatment as recommended by your Chardon Service Technician
  • Circulate this cleaning solution for at least 48 hours. Circulate for 96 hours in heavily fouled systems.
  • After the cleaning period, flush the loop using the guidelines in the first step. Continue flushing until the conductivity of the water in the loop equals that of the make-up water.
  • Retreat with the recommended closed loop treatment.


tips on flushing a closed loop by opening a drain valve near the lowest point in the system

How Can Scale From In A Closed Loop?

Closed loops rarely have scale problems, but mineral scale can form in systems with high hardness and alkalinity make-up sources. Mold surfaces are generally the hottest point in the system and high skin surface temperatures are prone to scale precipitation. Scale the thickness of a human hair can result in a 20% loss of heat exchange efficiency and that translates directly to an increased Cycle Time.

scale the thickness of a human hair can result in a 20% loss of heat exchange efficiency

But My Plastic Injection Mold Loops System Has A Closed Loop; Why does It Lose Water?

ASHRAE defines a “closed loop” as a system that loses less than 10% of its volume annually. Most plastic injection mold loops lose significantly more than 10% of their volume when mold tools are changed.

Figure out how much water your mold tools hold, then multiply that volume by the number of mold changes you make each year.

Add in cleaning and flushing of the water attachment manifold (you do flush the water manifold before connecting the new, clean mold, right?) and any other cleaning and maintenance practices that include water replacement.

Multiply that number by ten and compare it to your system volume.

How Does Ammonia Get Into A Closed Loop?

Ammonia is a metabolic by-product of aerobic respiration and evidence of bacterial and other forms of life.  More importantly to us, it is also a by-product of anaerobic respiration by nitrite reducing bacteria common to some closed loop systems.  The conversion of nitrite to ammonia is facilitated by bacteria and does not occur spontaneously.

The equation is: NO2 > NH4 + H2O

What Do I Do If I Find Ammonia In A Closed Loop?

Ammonia is extremely corrosive to copper and other yellow metals, especially in the presence of oxygen. Since most of our closed loop treatments are designed to scavenge the oxygen from the water, small amounts of ammonia (<5.0 ppm) can be tolerated. If your test results indicate that there is more than 5.0 ppm of ammonia in the water, or if the oxygen scavenger level is low, or if the treatment does not scavenge oxygen, then it will be necessary to flush the loop.

What Is The Best Way To Flush A Closed Loop?

While simply draining and refilling the loop seems easy and less time consuming, the consequences will far outweigh the time savings.  When a closed loop is completely drained, iron deposits are disturbed and oxygen is introduced into the system.

When the loop is refilled, the iron deposits break free and flow throughout the system, ready to form deposits where they may cause more problems than before. The oxygen that came in from the air promotes surface flash corrosion and makes the iron problems even worse.

A much better way to flush a closed loop is to open a drain valve near the lowest point in the system and flush water at 1 to 2 gallons per minute. Be careful not to flush too fast; pressure make-up valves are designed to maintain pressure in the loop and may not pass more than 1 or 2 gallons per minute.

Closely monitor the pressure on the loop for the first 20 minutes to ensure that the pressure will be maintained. Flush the loop at this rate until the conductivity of the draining water is equal to the conductivity of the make-up water.  Discontinue the flushing and treat as usual.

Chardon’s service department cannot be responsible to perform the flush. It is very time consuming and the pressure in the loop must be monitored very consistently. It is possible that the loop pressure will get too low and start to starve the circulation pumps. The flushing process could take days, weeks or months depending on the rate of water being drained/added to a loop. That is the reason that on-site personnel will need to do the flushing and monitoring.

Chardon will return when the on-site personnel inform us that the system water is very clear and clean. Chardon will then add closed loop treatment to the system.

Why Won’t The Iron Filter Out?

You may have colloidal iron. This will look like red-water iron but cannot be easily filtered. The iron has precipitated (turned to ferric iron) but the molecules formed do not stick together to form large enough pieces to settle to the bottom of a container or be trapped with normal filtration. This water/solid combination is called a colloidal mixture.

To test if you have this type of water, collect a sample in a clear glass container. Shine a flashlight beam through the water and see if you can see the light in the water. Then, let the water set overnight. If after setting overnight you can still see the beam of light as it passes through the water and there was no settling of material on the bottom of the container, the chances are very good that you have colloidal iron.

Using Glycol in Closed Loops

How does the glycol protect the loop from freezing?

Pure water freezes at 32° F, but a 60% solution of ethylene glycol pushes the freeze point down to -60° F. While the freeze point of pure glycol is only -39° F, the synergy between glycol and water results in a much lower freezing point. This is very important for closed loop systems that may be exposed to freezing conditions.


how ethylene glycol protects the loop from freezing by pushing the freeze point to -60 degrees F

What Is The Difference Between Freeze Protection & Burst Protection?

As the temperature of the water-glycol solution falls, the water will begin to freeze and “precipitate” out of solution causing the fluid to become slushy. Most systems can handle short periods of slush if the viscosity remains low. The “slush” period is termed burst protection. As the temperature continues to decrease, the glycol begins to freeze.

Unlike water which expands when it freezes, glycol contracts when it freezes. Therefore, when the glycol freezes, the volume in the system actually decreases. With freeze protection, there will not be any freezing of water or glycol in the mixture.

What Is The Difference Between Ethylene & Propylene Glycol?

Both types of glycol will provide adequate freeze protection in most systems. Ethylene glycol is the industry standard for closed loop freeze protection and is the product we use in most applications. Where food or potable water contact may be a concern, specify propylene glycol.

Propylene glycol is less toxic, breaks down more rapidly and is more environmentally friendly. Unfortunately, the freeze point of propylene glycol is not as low and its volume remains stable as it freezes and therefore does not offer the burst protection of ethylene glycol.

The visual differences may be as follows:

Type of Glycol  Color of glycol
Dowtherm SR-1 (ethylene glycol)  Fluorescent Pink
Dowtherm 4000 (ethylene glycol)  Fluorescent Orange
DowFrost (propylene glycol)  Water White (not much color at all)
DowFrost HD (propylene glycol for food applications low toxicity  Bright Yellow
Generic Inhibited Glycol (typically automotive antifreeze)  Light Green

Can I Use Automotive Antifreeze Instead of Glycol?

While automotive antifreeze does contain glycol, most brands are formulated to protect the aluminum components found in modern cars. The primary corrosion inhibitor in most automotive antifreeze blends is silicate. Silicates tend to form thick, visible passivation films that can adversely affect heat transfer. Silicates also tend to be gritty and can shorten the life of pump seals. Any type of corrosion inhibitor will require periodic replacement or supplementation.

Is There A Problem With Using Too Much Glycol?

Since glycol has a lower specific heat than water, higher concentrations of glycol in your closed loop water will reduce the heat carrying capacity of the system. Too much glycol will therefore increase energy costs as the system works harder to accomplish the desired heating or cooling.

Does The Glycol Protect The Metal In My Systems?

The glycol in a system does not protect any metal from corrosion. It is only the corrosion inhibitors that are added to the glycol that protect the metal. Glycol will not affect plastic but will affect aluminum (above about 150°F) and galvanized steel. The zinc in the galvanizing will react with most inhibitors and cause loss of the zinc coating leading to localized corrosion.

How Often Do I Need To Replace My Glycol?

The replacement cycle for glycol depends on the environment in which it is used. If the glycol is exposed to high temperatures (>250°F) or has significant amount of contamination, the cycle will be far more frequent.  It’s likely that a truly closed loop with no makeup can go for years without changing glycol. However, glycol will break down to glycolic acid over time and will require changing.

Even the glycol in your automobile requires periodic changing. Testing for iron, copper and ammonia levels will determine when to change the glycol. Additionally, the pH of the mixture may become acidic which is another strong indication of glycol breakdown.

Can I Add Specific Chardon Treatment To Loops Already Containing Inhibited Glycol?

Yes, however if the loop contains one of the special Dow brand glycols, additional inhibitors are not required. Many times the “green” colored glycol will benefit from addition of inhibitors.

How Can I Test For Glycol?

Using an instrument called a refractometer. It will display the freeze point of the glycol solution and then you can refer to the chart below to determine the percentage of glycol in the sample. Glycol makes closed loop water feel very slippery and it becomes sticky as the water dries. We recommend using ethylene or propylene glycol at 50% by volume. This will afford a freeze protection to -25° F (below zero).The table below will help you calculate how much glycol your system will require.

Installing & Using Corrosion Coupons in Closed Loops

What Do Corrosion Coupons In Closed Loops?

Corrosion coupons are pre-weighed and measured metal strips which are mounted in a special pipe system called a coupon rack. They are used to estimate the rate of metal corrosion by comparing the initial weight with the weight following 60, 90 or 120 days of exposure to the water in the system. Corrosion coupons are available in a wide variety of materials to assess corrosion in all types of systems.

corrosion coupons are used to estimate the rate of metal corrosion by comparing weight

What Do Corrosion Coupons NOT Do In Closed Loops?

Corrosion coupons are installed in a system with the intention of predicting the corrosion rate for the entire system. The obvious flaw with this reasoning is that the flow and temperature through a corrosion coupon rack will never duplicate the corrosion forces elsewhere in most systems. There is little effect on the coupon by temperature which would typically be a severe corrosive effect in actuality.

The most reliable indication of corrosion in the concentration of the total iron in the recirculating water. Even so, many facilities require coupon studies and below is the detailed procedure for installing and monitoring coupons.

Is There Anything Special I Need To Know About Corrosion Coupons In Closed Loops?

Corrosion coupon analysis involves a number of variables which may significantly affect the results of the analysis. Make sure the design of the system and the installation of the coupon rack will produce accurate test results.

  • Be careful not to touch the coupons. Oil from your hands will promote corrosion and bias the test results.
  • Maintain constant flow at 3-5 feet per second during the test period. Flow rates below 3 fps will allow particulates to settle on the coupon and will bias the results.  Flow rates in excess of 5 fps will erode soft metals such as copper and brass. In 3/4″ PVC pipe, 3-5 fps is equivalent to 5-8 gpm.
  • Avoid corrosion coupon tests in comfort cooling systems during the spring and fall. Constant, consistent flow provides more realistic results. Inconsistent flow will cause higher corrosion results.
  • Since the temperature of the water effects corrosion rate, installing the coupon rack after the heat source will result in higher corrosion rates. Conversely, installing the coupon rack after the tower will result in lower corrosion rates.
  • The order of coupons in the rack is important. Less noble metals such as carbon steel should be mounted upstream of more noble metals such as copper. This prevents copper ions from plating onto the iron coupons and causing artificially high corrosion rates.
  • Corrosion coupons installed in systems with oil or other hydrocarbon contamination will show artificially high corrosion rates due to sulfide attack. Corrosion coupon projects should be delayed until process leaks are under control or avoided altogether in contaminated systems.
  • The direction of water flow is important. Water should flow from the unattached end of the coupon toward the attachment end of the coupon.
  • Do not remove the coupons to look at them except at the end of the test period. Exposure to air, once the coupons are installed, can increase corrosion.

Before installing the coupons, complete the information on the coupon package. Turn off the system and carefully mount the coupons on the holder arms.  Use a paper or cloth towel to prevent the oils on your skin from impacting the results. Once installed, turn the flow to the rack back on and adjust the flow rate to 3-5 fps. Maintain constant flow throughout the study. Store the coupon envelopes in the controller or in a dry place near the coupon rack.

Remove the coupons after 60, 90 or 120 days as specified by the study. Carefully remove and dry each coupon on a paper towel. Take care not to remove material deposited on the coupon because deposits are an important part of the evaluation. Place the coupon into the original envelope without the plastic bag. Record the date of removal and send the coupon back to the Chardon Technical Support Laboratory as soon as possible.

The results of the corrosion coupon analysis will be presented on a Laboratory Report for and include a written analysis, a photograph of the coupon, and a corrosion rate in mills per year, or mpy. Use the table below to evaluate the results from your study.

Contact Our Closed Loop Water Treatment Company to Learn More

Contact Chardon Laboratories to learn more about chemical treatment for closed loop systems and our other effective treatment solutions today.