What Causes Air in Hot Water Heating System?

Here are several causes of air in a hot water heating system. Some of the most common causes include:

1. Air bleeding: When the system is initially installed or when components are replaced or repaired, air may be trapped in the system. This air can be removed by bleeding the system, which involves purging air from the piping and radiators to ensure efficient and safe operation.
2. Pump issues: If the pump in the hot water heating system is not properly calibrated or is damaged, it may not circulate the hot water properly through the radiators or baseboard heaters. This can lead to air pockets forming in the system.
3. Boiler issues: If the boiler in the hot water heating system is not operating properly, it may not heat the water to the desired temperature. This can result in air being drawn into the system as the hot water cools down.
4. Pipes and fittings: If there are any leaks or improper connections in the hot water heating system's pipes or fittings, air can enter the system through these openings.
5. Thermal expansion: As the hot water expands and contracts during operation, air may be drawn into the system through the expansion tank or other components.
6. Improper maintenance: If the hot water heating system is not maintained regularly, deposits and scale can build up in the pipes and radiators, reducing the system's efficiency and leading to air being drawn into the system.

To address these issues, it's recommended to have a professional heating contractor or technician inspect and service the hot water heating system regularly. They can identify the cause of the air in the system and take appropriate measures to rectify the problem.