Heat Pump Leaking Water? What's Normal and What Needs Repair
A heat pump leaking water outside in winter is usually defrost meltwater. Water inside points to a clogged drain, failed condensate pump or frozen coil. Here is how to tell the difference and what to do.
A heat pump leaking water can be completely normal or a sign of a problem, depending on where the water is and what season it is. Water dripping from the outdoor unit in winter is usually defrost meltwater. Water inside the house, near an air handler or under a mini-split head, almost always means a drain, pump or airflow problem that needs attention. Here is how to tell which is which.
Key Takeaways
- Outdoor water in winter is usually normal. Defrost cycles melt frost off the coil.
- Indoor water is not normal. It points to a clogged drain, failed pump or frozen coil.
- Act fast on indoor leaks. Water damages ceilings, walls and floors quickly.
- Ice is a different problem. Ice that never clears needs service.
Is It Normal for a Heat Pump to Leak Water Outside?
Usually, yes. In heating mode, the outdoor coil gets colder than the air and collects frost. During defrost, the unit melts that frost, and water drips out the bottom. You may also see steam. Read heat pump defrost mode explained for the full cycle.
In summer, the outdoor unit should stay mostly dry. You may see a little condensation on the larger refrigerant line, which is normal.
| Where | Season | Usually |
|---|---|---|
| Outdoor unit, dripping | Winter | Normal defrost meltwater |
| Outdoor unit, heavy ice buildup | Winter | Problem: drainage, defrost or refrigerant |
| Refrigerant line, light sweating | Summer | Normal condensation |
| Indoor air handler or head | Summer | Problem: drain, pump or frozen coil |
| Indoor, in winter | Winter | Problem: often a frozen drain line outside |
Why Is My Heat Pump Leaking Water Inside?
In cooling mode, the indoor coil pulls moisture from the air. That water drips into a pan and flows out a drain line or into a condensate pump. When any part of that path fails, water ends up where it should not.
- Clogged drain line: algae, dust and debris block the line. The most common cause.
- Failed condensate pump: the pump stops lifting water out.
- Cracked or rusted drain pan: common in older air handlers.
- Frozen indoor coil: low airflow or low refrigerant freezes the coil; it melts and overflows.
- Dirty filter: restricts airflow and leads to freezing.
- Poor drain slope: lines installed without enough pitch hold water.
- Frozen drain outlet: in winter, an exterior drain outlet can freeze and back up.
Water dripping from a mini-split head on the wall? See our dedicated guide to mini-split leaking water.
Seeing water on the floor or ceiling now? Request a heat pump leak repair, and turn the system off until it is checked to limit damage.
What Should You Do Right Away?
- Turn the system off at the thermostat.
- Catch the water with towels or a bucket.
- Check the filter. If it is clogged, replace or clean it.
- Look for ice on the indoor coil or refrigerant lines. If you see ice, leave the system off so it thaws.
- Check whether a condensate pump is humming but not pumping.
- Call for service if the leak continues or you see ice.
Do not try to add refrigerant or open sealed panels. Refrigerant work requires an EPA-certified technician. Keep water away from electrical parts and outlets.
What About Ice on the Outdoor Unit?
Some frost is normal. A solid block of ice that never clears is not. Causes include roof runoff, a unit sitting too low, a blocked drain path, a failed defrost sensor, a stuck reversing valve or low refrigerant. Clear snow gently, never chip ice, and call for service. Our pillar on heat pump maintenance covers how to keep the outdoor unit clear.
How to Prevent Heat Pump Leaks
- Check or clean filters monthly in heavy use.
- Have drain lines flushed during the spring tune-up.
- Test condensate pumps each cooling season.
- Keep the outdoor unit raised and its drain path clear of ice.
- Insulate exterior drain lines that can freeze.
Per DOE's air conditioner maintenance checklist, replacing a dirty filter can lower energy use by 5% to 15%, and clear drains and coils keep the system working as designed. Per DOE guidance on air-source heat pumps, a well-maintained heat pump can use 10% to 25% less energy than a severely neglected one. As of 2026, many newer systems also flag drain or sensor errors on their apps, so check yours if it has one.
Stop the Leak Before It Spreads
A heat pump leaking water outside in winter is usually fine. A heat pump leaking water inside is not, and it gets worse the longer it runs. Most leaks come down to a clogged drain, a failed pump or a frozen coil, all fixable.
Jose has worked in HVAC since 2015. HomePros gives a written flat price before any repair starts. Schedule heat pump leak repair, or call (781) 426-8428. More in our heat pumps in Massachusetts guide.
Looking for the complete guide?
Heat Pumps in Massachusetts: A North Shore Homeowner's Guide