How to Properly Pipe and Control a Glycol Makeup Unit

July 21, 2021

This article will help the reader better understand the proper installation of a glycol makeup unit, such as the Wessels Glycol Feeder. It will also address how the controls work to provide the proper system pressure.

What is a Glycol Makeup Unit or Glycol Filling Station?

Wessels Glycol Makeup Unit

The glycol makeup unit is a pre-packaged system that allows for pre-mixed glycol solutions to be introduced into a system with the purpose of maintaining the proper system pressure. These packages include a glycol fill pump, a glycol holding tank, a pressure regulating valve, interconnecting piping and a simple control system.

Why should I install the Glycol Makeup Unit in my system?

When a system is filled with a glycol mixture such as 40% DOWFROST HD, it is important to maintain the proper concentration of the glycol. As air is removed from the closed system, the pressure in the system drops. At that time, the makeup system adds fluid to the system to bring the pressure back up to the desired setting. Adding water to your glycol system will reduce the concentration over time and could result in lost protection in the system. Having a glycol makeup unit with a 40% pre-mixed solution of 40% DOWFROST HD in the glycol holding tank ensures that the concentration is kept at the desired levels.

Where should I install the Glycol Makeup Unit in my system?

The glycol makeup unit should be installed in the same location as the typical pressure regulating valve would be in a water system as it is serving the same purpose. As shown in the diagram, the unit should be piped at the air separator and expansion tank. It is often piped with the air separator vent line to help vent any air that might be introduced by the glycol makeup unit.

Glycol Makeup Unit


What type of piping should I use when piping my Glycol Makeup Unit?

Piping is typically steel or copper. Be sure to check the connection fittings to ensure any opportunity for galvanic reaction is eliminated. This article can help you choose the best piping material based upon the glycol you use in your system. To learn more about which glycol is best for your application, click here.

How is the Glycol Makeup Unit controlled?

There are four main components to the glycol makeup unit control system. All of these items are pre-piped in the glycol piping or in the makeup tank. The first component is the control panel which is nothing more than a basic starter with a pilot light, a low-level horn and a couple sensors. One of the sensors is a low-level sensor located in the makeup tank that will stop the pump if low levels of fluid are detected. This protects the pump from running dry as well as signals the horn to make the maintenance team aware that the fluid is low. The second sensor acts as a high pressure sensor and is located on the pump discharge. This sensor stops the pump once the pressure limit is hit. The last component is the pressure regulating valve. This valve is a mechanical means of setting the desired pressure at the discharge of the glycol makeup unit, which is the same as the system cold fill pressure. The valve is open when the pressure downstream of the valve is below the setting and is closed when the pressure downstream of the valve reaches the set pressure.

These four components work together to provide the proper fill pressure, to start and stop the pump as pressure drops and is recovered, and to stop the pump if the glycol tank requires more premixed glycol solution.

The glycol makeup unit, or glycol filling station, is a critical part of your systems operation. It helps maintain the proper glycol solution which helps keep your system protected at all times. It’s a low-cost solution to keep your system in tiptop shape!



Josh earned his BS degree in Mechanical Engineering from Case Western Reserve University. He also holds a PE license. Josh has been an integral part of the team for 16 years. In his spare time, Josh spends time with his wife and four daughters, plays golf, volunteers with local charities and plays an active role in his church.

Go Glycol Pros LogoGo Glycol Pros is a distributor of DOW® heat transfer fluid for over 20 years. We sell glycol online with no accounts or order minimums required. Available in 275 gallon tote, 55 gallon drum or 5 gallon pail, high purity DOW antifreeze is premixed with deionized water (DI water) at our in-house facility and ships out within just one business day. Our inhibited glycols include: DOWFROST HD propylene glycol, DOWFROST food grade propylene glycol and DOWTHERM SR-1 ethylene glycol.

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Disclaimer: Go Glycol Pros and it’s affiliates can not be held liable for issues caused by use of the information on this page. While the- information comes from many years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions that result from this information. Please feel free to contact us if you do have any questions.