A puddle on the utility room slab is one of those problems that looks small on Saturday and costs real money by Tuesday. Water finds subfloor, drywall, and insulation faster than most homeowners expect, and in a Puget Sound crawl space or attic it does that damage where nobody can see it.
So here is the honest version: your heat pump is supposed to make water. The question is only whether that water is leaving the way the manufacturer designed, or leaving through your ceiling.
Where the water comes from in the first place
When a heat pump runs in cooling mode, the indoor coil gets cold. Warm, humid house air blows across it and moisture condenses out — exactly like a cold glass of water on an August afternoon. In our climate, with typical summer relative humidity in the 60 to 85 percent range, a working system can pull several gallons a day out of the air on a hot week.
That water lands in a drain pan under the coil, runs out a PVC drain line by gravity, and exits somewhere harmless: a floor drain, a condensate pump, a laundry standpipe, or outside through a wall. Nothing about that process is exotic. It's a slope, a pipe, and a trap. Which is exactly why it fails — it's the least glamorous part of the system and the part nobody looks at.
In heating mode, the roles reverse. The outdoor coil gets cold and frosts up, and the defrost cycle melts that frost onto the ground. Steam and dripping outside in winter is normal, not a leak. If you want the full explanation of that, our post on a heat pump not heating covers what defrost should and shouldn't look like.
Normal: what water should be doing
- A steady trickle from the condensate line outside or into a floor drain during cooling season.
- A slightly damp coil and clean, empty drain pan.
- Water dripping off the outdoor unit in winter during and after a defrost cycle.
- A condensate pump clicking on every so often and quietly emptying itself.
Not normal: the seven causes we actually find
1. A clogged condensate drain line
This is the number one cause, and it's not close. Dust from the air stream mixes with condensate and forms sludge, then algae and biofilm grow in the standing water. The line plugs, the pan fills, and water goes over the edge onto whatever is below. Some systems have a float switch that shuts the unit down before that happens — if your heat pump keeps stopping in hot weather and there's water in the pan, that switch is doing its job.
2. A rusted or cracked drain pan
Older air handlers used metal pans. Twenty years of sitting wet in a damp Western Washington crawl space or garage does what you'd expect. Secondary plastic pans crack, especially if someone stepped on one during an attic job. A pan can't be patched reliably — it gets replaced.
3. A failed condensate pump
If your air handler sits below the nearest drain — common in Puget Sound basements and daylight-basement homes — a small pump moves the water uphill. Pumps have impellers, floats, and check valves, and they all eventually quit. When one dies, the pan overflows within a day or two of steady cooling.
4. A frozen indoor coil
A coil encased in ice doesn't drip — it dumps, all at once, when the system shuts off and the ice melts faster than the pan can drain. Freezing usually traces back to restricted airflow or low refrigerant. Either way, the water is a symptom, not the disease.
5. A filthy air filter or blocked return
Starve the coil of airflow and it runs colder than designed, ices, and then floods. This is the cheapest possible cause and the one homeowners can genuinely rule out in five minutes. Pull the filter. If light doesn't pass through it, that's your first suspect.
6. A disconnected, sagging, or badly sloped drain line
Condensate drains work on gravity alone. A line that got bumped during a water heater replacement, a sagging flex section holding water, or a missing trap that lets the blower push air backward through the pipe will all put water where it doesn't belong. We see this most often on systems installed in a hurry.
7. A refrigerant leak
Low refrigerant drops coil temperature and pressure, ice forms, ice melts, floor gets wet. Refrigerant leaks are the one item on this list that also quietly wrecks your compressor, so "it only leaks a little water" isn't a reason to postpone it.
What to do in the next ten minutes
- Turn the thermostat off. A running blower keeps making condensate.
- Kill the breaker to the air handler if water is anywhere near electrical connections.
- Get the water up. Towels, shop vac, whatever's handy. Standing water on a slab wicks into baseboard and framing.
- Check the filter. Replace it if it's dirty.
- Look at the drain pan and line. Standing water in the pan means the drain is plugged.
- Call it in. Reach us at (253) 785-4622 — Monday through Friday, 8 to 6, with same-week scheduling in most of our service area.
What not to do: don't shove a coat hanger or pressurized water down the drain line. Coil fins and plastic pans are soft, and a $200 clog turns into a $900 pan replacement fast.
What these repairs cost around Puget Sound
Heat pump repair runs $150 to $1,500 typical in standard markets, $175 to $1,800 in affluent markets like Seattle, Maple Valley, Normandy Park, Black Diamond, Steilacoom and Fircrest, and $200 to $2,000 in luxury markets like Bellevue, Gig Harbor and Fox Island. Where a specific job lands depends on the fix:
| The problem | Where it usually falls in the range |
|---|---|
| The problemClogged drain line, dirty filter, cleared trap | Where it usually falls in the rangeBottom of the range |
| The problemFloat switch replacement, new condensate pump | Where it usually falls in the rangeLower middle |
| The problemDrain pan replacement (access-dependent) | Where it usually falls in the rangeMiddle to upper |
| The problemCoil cleaning after repeated freeze-ups | Where it usually falls in the rangeMiddle |
| The problemRefrigerant leak diagnosis and repair | Where it usually falls in the rangeUpper end |
You get a price before any work starts. That's the whole point of a diagnostic visit.
Why Puget Sound homes see this more than you'd think
Our crawl spaces and garages are damp for most of the year. Damp air plus a metal pan equals corrosion, and corrosion equals pinholes. Add attic air handlers in 1980s and 1990s split-levels where the secondary pan is out of sight, and you get leaks that show up first as a ceiling stain in a bedroom, not a puddle you can see.
Also worth naming: the mild marine climate means many systems here run long, gentle cooling cycles rather than short brutal ones. Long cycles produce a lot of condensate. That's good for comfort and dehumidification — but it means the drain has a job every single day of summer, and a neglected drain will eventually fail.
How to keep it from happening again
- Change filters on schedule. Every one to three months depending on type, pets, and construction dust.
- Get maintenance twice a year if you're near salt water — Des Moines, Burien, Steilacoom, Gig Harbor, Dash Point. Once a year everywhere else.
- Have the drain line flushed as part of that maintenance. It takes minutes and prevents the most common failure on this list.
- Keep the pan clear. No stored boxes, no paint cans on top of the air handler.
- Ask about a float switch if your system doesn't have one. A shutdown is annoying. A flooded ceiling is expensive.
When a leak is really a replacement conversation
Sometimes the water is the messenger. If the system is 15-plus years old, the pan is rusted through, the coil is dirty enough to freeze, and it's on R-22 refrigerant, you're not looking at one repair — you're looking at a sequence of them. Our rule of thumb: under 10 years old, repair almost always wins. At 12 to 15 years with a four-figure repair in front of you, run the numbers on replacement, which is $10,000 to $16,000 in standard markets and comes with a 10-year parts and labor warranty. The full breakdown lives in our Washington heat pump cost guide.
Rebate programs can also change that math on a conversion. Programs change — we confirm your current eligibility and handle the paperwork, and from April 2, 2026 PSE rebates require a PSE-certified installer, which Varsity is.
Get a real number
Want a ballpark before anyone comes out? The instant estimate tool gives you Good, Better and Best starting prices in about 60 seconds. For a leak that's happening right now, request service or call (253) 785-4622. We're owner-operated out of Federal Way, we pull the permit on every install, and we'll tell you plainly whether you need a $200 drain clearing or a new system — including when the honest answer is the cheap one.