Frequently asked questions

Understanding design life is essential before adding propylene glycol. Less expensive propylene glycols often hold a shorter design life of three to five years, whereas premium propylene glycol heavy-duty (PGHD) holds a design life of up to 15 years.

As propylene glycol degrades it becomes acidic and begins to attack metal components. ig-loo glycol contains a higher-quality HD inhibitor that acts as a buffer, keeping the system water’s pH in the ideal 8.0–8.5 range. Once system pH drops below 6.5, inhibitors with buffering agents must be added to restore protection.

Boiler manufacturers often advise that glycol should make up no more than 50% of the system’s volume, with some high-efficiency (HE) boiler applications reduced to 35%.

The right concentration depends on the freeze or burst protection your lowest expected temperature requires, balanced against the fact that more glycol means higher viscosity and reduced heat transfer. Our calculator sizes the concentration for your target temperature, and our team can confirm it against your equipment’s requirements.

Burst protection is required in HVAC systems when the system will sit inactive while temperatures are below the freezing point of the solution. As the temperature drops below freezing, ice crystals begin to form and the glycol becomes more concentrated, creating a flowable slush that expands into the system’s available expansion volume rather than bursting pipes.

A 30% glycol solution typically provides adequate burst protection, with the slush remaining fluid down to about −60°F for ethylene glycol or −20°F for propylene glycol. Burst protection always requires a notably lower concentration than full freeze protection. Use the freeze & burst calculator to size it for your lowest expected temperature.

Yes. Glycol has a higher viscosity than water, so too much of it reduces the effectiveness of water flowing through the pipework and lowers heat-transfer capability. Excess glycol forces pumps and heat exchangers to work harder, which can lead to overheating and component failure.

The goal is the lowest concentration that still delivers the freeze or burst protection your system needs, not the highest. Size it deliberately rather than over-dosing “to be safe.”

Yes. Pre-mix glycol is not designed to lift and capture magnetite; it’s designed to keep system water from freezing during the coldest months. Comprehensive system protection requires more than antifreeze:

• A cleaner with surfactants to dislodge magnetite particles
• System flushing to remove the loosened debris
• A magnetic dirt filter for ongoing, continuous protection
• Inhibitors that form a protective layer and maintain pH neutrality
• Regular testing (annual for residential systems) of chloride, copper, iron, hardness, and pH

Sub-Frost can test your fluid and recommend the right inhibitor top-up or recover-and-replace schedule.