Why Is My AC Leaking Water? (Treasure Valley Homeowner Guide)

Water Around Your AC Is Never Something to Ignore

Finding a puddle of water near your air conditioner — whether it’s the indoor air handler in your utility room or the outdoor condenser unit on the side of your house — is a clear sign something isn’t right. While some moisture around an AC system is normal, pooling water or active dripping is not.

Left unaddressed, a leaking AC can cause water damage to your walls, floors, and ceiling, and can create the conditions for mold growth inside your home. The faster you identify the cause, the better.

Here’s what’s most likely causing it — and what to do.

Is Some Water Around My AC Normal?

A small amount of condensation on the refrigerant lines or the area immediately around the outdoor unit during humid weather is normal — similar to a cold glass of water sweating on a warm day. What is not normal:

• Puddles or pooling water under the indoor air handler
• Water dripping from the ceiling or walls near the air handler
• Steady dripping from the outdoor unit (not just light condensation)
• Water stains appearing on drywall or flooring near the unit

If you’re seeing any of those, read on.

Common Causes of a Leaking AC in the Treasure Valley

1. Clogged Condensate Drain Line

This is by far the most common cause of AC water leaks — and it’s especially prevalent in the Treasure Valley. As your AC runs, it pulls moisture out of your home’s air. That moisture collects on the evaporator coil, drips into a drain pan, and flows out through the condensate drain line.

Over time, algae, dust, and debris build up inside the drain line and can cause a full blockage. When water can’t drain, the pan overflows — and you end up with water on your floor, in your walls, or dripping from the ceiling below.

In Boise’s dry, dusty climate, particulate buildup in the drain line tends to happen faster than in more humid regions. Homes that skip annual maintenance are especially prone to this issue.

Signs this is the issue: water pooling directly under the indoor unit, a musty smell near the air handler, or an automatic shutoff triggered by your overflow safety switch (your AC stops working entirely).

2. Frozen Evaporator Coil Thawing

When an evaporator coil freezes — due to restricted airflow, low refrigerant, or a dirty filter — it can appear dry while the system runs. But when the system cycles off, that ice melts all at once, producing more water than the drain pan and line can handle.

If you notice water appearing after your AC shuts off rather than while it’s running, a thawing frozen coil is likely the cause. The underlying problem (what caused the freeze in the first place) still needs to be diagnosed and repaired.

3. Damaged or Rusted Drain Pan

The drain pan sits beneath the evaporator coil and catches condensation as it drips off. In older systems, the pan can rust through or develop cracks — causing water to leak out before it ever reaches the drain line.

If your system is more than 10 years old and you’re seeing water leaks that don’t clear up after drain line maintenance, the pan itself may need to be inspected and replaced.

4. Disconnected or Improperly Installed Drain Line

Sometimes the drain line simply comes loose from the fitting — particularly in systems that have been recently serviced or in homes where vibration from the air handler has worked a connection loose over time. This results in water draining directly onto the floor or into the wall cavity rather than through the intended line.

5. Low Refrigerant Causing Coil to Freeze

As discussed above, a frozen coil is a common cause of water leaks when the ice melts. And one of the most common reasons a coil freezes is low refrigerant — which is almost always the result of a leak somewhere in the system.

If you’ve had repeat water leak issues and they keep coming back, refrigerant could be the root cause. A technician can check refrigerant levels and locate any leaks during a service call.

6. High Indoor Humidity (Less Common in Boise)

In extremely humid conditions, an AC system can produce more condensation than the drain system is designed to handle. This is rare in the Treasure Valley given the region’s generally dry climate, but it can occur during unusually humid stretches or in homes with high indoor moisture sources (cooking steam, indoor plants, poor ventilation).

What to Do Right Now If Your AC Is Leaking

If you find water around your AC unit, take these steps before calling for service:

• Turn off the AC system at the thermostat — running a leaking system can cause further water damage and may damage the equipment
• Place towels or a bucket to catch water if it’s actively dripping
• Check and replace your air filter — a severely restricted filter can cause coil freezing and contribute to overflow
• Check whether your system has a secondary drain pan (common in attic-mounted units) — if it’s full, water may be close to overflowing into your ceiling
• Do not attempt to clear the drain line yourself with a wet-vac unless you know where the access port is — improper attempts can push debris further into the line

Once you’ve taken those steps, call Drake Mechanical. A clogged condensate line is one of the faster repairs we handle, and catching it early prevents far more expensive water damage repairs down the road.

How to Prevent AC Water Leaks

Most condensate drain issues are entirely preventable with routine maintenance. Here’s what helps:

• Schedule annual AC maintenance — a technician will flush the drain line, clean the coil, and check the drain pan as part of a standard tune-up
• Change your air filter regularly — every 30–90 days depending on your home and usage
• Consider a condensate drain treatment tablet — placed in the drain pan, these slow algae growth and reduce blockage frequency
• Ask about a condensate overflow shutoff switch — if your system doesn’t have one, adding one can prevent water damage by shutting the system down before a full overflow occurs

Drake’s Duck Club maintenance plan includes annual HVAC inspections that cover condensate drain cleaning — a straightforward way to stay ahead of this issue.

Need AC Repair in the Treasure Valley?

A water leak is one of the clearer signs your AC needs professional attention. For a full overview of AC repair in Boise and the surrounding area — including costs, what to expect, and how Drake Mechanical approaches every job — visit our main AC repair page:

Frequently Asked Questions

Is a little water under my AC normal?

A very small amount of condensation immediately under the outdoor unit during hot weather can be normal. Puddles under the indoor air handler, water dripping from the ceiling, or any ongoing water accumulation inside the home is not normal and should be evaluated.

Can I still run my AC if it’s leaking water?

We recommend turning it off. Running a leaking system risks water damage to your home’s structure, flooring, and drywall — and if the leak is related to a frozen coil, running the system can cause compressor damage as well.

How do I know if my condensate drain line is clogged?

Common signs include water pooling under the indoor unit, a musty smell near the air handler, and in many systems, an automatic shutoff (the AC simply stops cooling). A technician can confirm with a quick inspection and clear the line in most cases during a single visit.

How much does it cost to fix a leaking AC?

Clearing a clogged condensate drain line is typically one of the more affordable AC repairs. More involved fixes — like replacing a drain pan or addressing a refrigerant leak causing coil freezing — will run higher.

Will homeowner’s insurance cover water damage from a leaking AC?

Policies vary, but many homeowner’s insurance plans cover sudden and accidental water damage. Damage from a slow leak that was left unaddressed over time is often excluded. This is another reason to act quickly when you spot a water leak — both to protect your home and to preserve any potential insurance claim.