How to Replace Antifreeze in a Boiler

Boilers in harsh winter conditions need antifreeze to avoid pipe ruptures.

Boilers in buildings that reside in harsh winter climates need antifreeze to protect them from possible pipe ruptures. The antifreeze used in boilers is not the same as that used for cars and other motor vehicles. In fact, these types of antifreeze can cause corrosion to the system. The exact steps to replace antifreeze and recommended antifreeze solution depend on the make and model of your system. However, all boilers require the same basic preparation steps.

Things You'll Need

• Boiler antifreeze
• 10-gallon bucket
• Water
• Garden hose
• Submersible pump and hose

Instructions

1. Turn off the boiler and all water lines that flow into the unit. This differs depending on the type of unit. In general, gas boilers have a gas shut-off valve located somewhere near the bottom. The water lines may need to be shut off at the water main depending on your system. Allow the system to cool for several hours before attempting to add antifreeze.

2. Mix the antifreeze and water solution in the bucket. The exact proportions of water to antifreeze depend on the type of antifreeze used and the size of your boiler. Consult the boiler documentation and the instructions on the antifreeze for proper mixing proportions.

3. Drain the water from the boiler. Attach a garden hose or similar to the boiler drain valve. Many modern boilers have threaded faucets that readily accept screw on hoses. Run the other end of the hose to a drain or outside. Open the drain valve completely to drain the system. This may take several hours depending on the size of the boiler.

4. Locate the intake valve or port on the boiler. For most boilers, this is somewhere on top. Consult the boiler documentation if you have trouble locating the valve or port.

5. Insert one end of the submersible pump hose into the pump. Insert the other end into the intake valve or port on the boiler. Submerge the pump in the bucket that contains the water and antifreeze solution. Plug in the pump. Allow the pump to pass the solution into the boiler.

Tips & Warnings

• Some boiler have intake ports large enough to pour in the solution directly with the aid of a funnel.

References

• Aurora Power: Boiler Antifreeze
• Heating Piping Air Conditioning (HPAC) Engineering: Boiler Inspection, Maintenance, Safety