Turning on the furnace as temperatures drop should mean cozy warmth—not unexpected puddles. If you notice water around your furnace early in the heating season, several issues could be at play. Here are five common reasons why furnaces may start leaking water as they get back to work.

1. Condensation Leak in High-Efficiency Furnaces

  • Why It Happens: If you have a high-efficiency furnace (typically 90% AFUE or higher), it produces condensation as a byproduct. This condensation should drain properly, but clogs or leaks in the drainage tubing or collector box can cause water to pool around the furnace.
  • How to Check: Look at the exhaust pipe—if it’s plastic (PVC), it’s likely a high-efficiency model. Check for any blockages or damage in the drain lines.
  • Solution: Clear any clogs or call a professional if you’re unsure about handling furnace components.

2. Clogged Condensate Drain

  • Why It Happens: Condensate drains are a part of your HVAC system designed to handle the moisture produced during cooling and heating. Over time, these drains can get clogged with dirt, mold, or debris, leading to water backing up and leaking around the furnace.
  • How to Check: Inspect the drain line to see if there’s any visible clogging, or check for slow drainage.
  • Solution: Flush the drain line with a mild bleach solution or distilled vinegar, or call an HVAC professional to clean it.

3. Humidifier Leak

  • Why It Happens: Many homes in Philadelphia use humidifiers attached to their HVAC systems to maintain comfortable indoor humidity during winter. When humidifiers aren’t serviced regularly, issues like loose connections or clogged water lines can lead to leaks.
  • How to Check: Look for signs of leaking around the humidifier. If there’s water buildup near it, the humidifier may be the culprit.
  • Solution: Check the water line connections, or have your humidifier inspected and serviced to prevent further leaks.

4. Ventilation or Exhaust Problems

  • Why It Happens: Poor ventilation can lead to excess condensation that doesn’t have a clear way to escape. In older furnaces or improperly installed systems, this moisture can pool and eventually leak around the furnace.
  • How to Check: Inspect the exhaust vent pipe for any blockages or misalignment, particularly if your furnace is in an enclosed space.
  • Solution: Clear any blockages in the exhaust vent or have a professional evaluate the ventilation setup to ensure safe and efficient airflow.

5. Leaky Secondary Heat Exchanger

  • Why It Happens: High-efficiency furnaces have a secondary heat exchanger to improve heating efficiency. However, if this component is cracked or leaking, it can cause water to pool around the furnace. This is often a more complex issue found in older high-efficiency units.
  • How to Check: A leaking secondary heat exchanger usually isn’t visible from the outside, so this issue typically requires professional inspection.
  • Solution: Call a licensed technician to inspect the heat exchanger. Replacing or repairing this component may be needed if it’s damaged.

Final Thoughts

Water around your furnace early in the season can indicate anything from minor blockages to larger issues that require professional attention. Preventive maintenance is key, especially in regions like Philadelphia, where heating systems work hard throughout the winter. If you’re concerned about a furnace leak, contacting a reliable HVAC company like McCorry Comfort ensures a thorough diagnosis and helps keep your home safe and warm all season long.