Quick answer: A goodman furnace leaking water is almost always caused by a blocked condensate drain line, a failed condensate pump, or a cracked drain pan. Clear the clog or replace the faulty component to stop the leak in most cases.
Quick-Diagnosis Table
| Symptom | Most Likely Cause | DIY Difficulty |
|---|
| Puddle directly under furnace | Clogged condensate drain line | Easy |
| Water near small box/reservoir | Failed condensate pump | Moderate |
| Shallow tray overflowing | Cracked or full drain pan | Easy |
| Water dripping from flue pipe area | Improper flue/vent pipe slope | Moderate |
| Leak only during heating season | Humidifier malfunction | Moderate |
| Wet insulation on refrigerant lines | Frozen/thawing evaporator coil | Moderate–Hard |
Repair vs. Replace Cost Guide
| Part / Repair | DIY Part Cost | Pro Labor + Part |
|---|
| Condensate drain line flush | $0–$10 (vinegar/brush) | $75–$150 |
| Condensate pump replacement | $25–$60 | $150–$300 |
| Drain pan replacement | $15–$40 | $100–$200 |
| Flue pipe re-slope/repair | $10–$30 (fittings) | $150–$350 |
| Humidifier water panel/valve | $10–$40 | $120–$250 |
| Evaporator coil cleaning | $15–$30 (coil cleaner) | $200–$500 |