A leaking furnace is a common issue, especially early in the heating season, and it’s important to address it quickly to avoid damage or system inefficiency. Here’s a step-by-step troubleshooting guide to help you figure out why your furnace might be leaking water and how to resolve it.

1. Identify the Type of Furnace

Before diving into the cause of the leak, it’s helpful to know whether you have a high-efficiency furnace or a conventional one.

  • High-Efficiency Furnace: Typically uses PVC exhaust pipes and produces condensation during operation.
  • Conventional Furnace: Uses metal exhaust pipes and does not typically produce water under normal conditions.

The type of furnace will determine whether condensation or another issue is the likely culprit.

2. Check for Common Causes

A. Condensation Leak (High-Efficiency Furnaces)

  • Why It Happens: High-efficiency furnaces create condensation that should drain away. If the drain lines, collector box, or condensation pump are clogged or damaged, water can leak.
  • How to Fix It:
    • Inspect the condensation drain lines for clogs or kinks.
    • Flush the lines with warm water or vinegar to remove buildup.
    • Check the condensation pump (if present) for proper operation.

B. Clogged or Disconnected Drain Line

  • Why It Happens: Whether you have a high-efficiency furnace or a connected AC unit, drain lines can clog with debris or disconnect, causing leaks.
  • How to Fix It:
    • Look for visible clogs or disconnections in the PVC or flexible drain tubing.
    • Reconnect loose lines securely and clear any obstructions.

C. Leaking Humidifier

  • Why It Happens: If your furnace is paired with a whole-house humidifier, leaks can occur if the water line, valve, or pad malfunctions.
  • How to Fix It:
    • Inspect the humidifier’s water line and valves for leaks.
    • Replace the water pad if it’s clogged or damaged.

D. Ventilation Issues (Poor Exhaust Flow)

  • Why It Happens: Improper venting can cause condensation to accumulate and leak. Blocked or misaligned exhaust pipes can also lead to water buildup.
  • How to Fix It:
    • Check the exhaust vent for blockages or damage.
    • Clear obstructions and ensure proper alignment of the vent pipe.

E. Malfunctioning Heat Exchanger

  • Why It Happens: In rare cases, a cracked heat exchanger in a high-efficiency furnace can cause water or other fluids to leak. This is a serious issue that requires professional attention.
  • How to Fix It:
    • If you suspect a heat exchanger issue, turn off the furnace and call a licensed HVAC technician immediately.

3. Prevent Future Leaks

  • Schedule Regular Maintenance: Annual HVAC check-ups help catch issues like clogged drain lines or failing parts before they become major problems.
  • Replace Air Filters Regularly: A dirty filter can restrict airflow, causing the system to work harder and potentially leading to leaks.
  • Inspect Components Periodically: Check drain lines, the humidifier, and exhaust vents every few months for signs of wear or clogs.

When to Call a Professional

If troubleshooting doesn’t resolve the issue or if you suspect a serious problem (like a cracked heat exchanger), it’s time to contact a professional. A licensed HVAC technician can diagnose and fix the problem safely, ensuring your system is ready to handle the cold months ahead.

Addressing a leaking furnace early can prevent costly repairs and keep your system running efficiently all winter long. If you’re in the Philadelphia area and need assistance, McCorry Comfort is ready to help with reliable furnace repair and maintenance services!