Usually safe to drive

Puddle of Water Under Your Car? Usually Nothing to Worry About

A clear, odorless puddle of water under your car - especially toward the front passenger side after running the air conditioning - is almost always harmless condensation from the A/C system. As the A/C cools humid cabin air, water collects on the cold evaporator and drains out under the car, exactly like droplets forming on a cold glass. The key is making sure it's actually clear water and not a colored or oily fluid, which would point to a real leak.

Common causes

1
A/C evaporator condensation (normal)
By far the most common cause. Running the A/C produces clear water that drains out under the passenger side near the firewall. A puddle the size of a dinner plate or smaller, especially on hot, humid days, is completely normal.
2
Exhaust condensation (normal)
Water is a byproduct of combustion. On cold starts or short trips you may see clear water dripping from the tailpipe or pooling at the rear - harmless and a sign the engine is running efficiently.
3
Heater/defroster condensation
Running the defroster or heater in cold, damp weather can also produce small amounts of condensation that drains outside the cabin.
4
Windshield cowl or sunroof drains
Rainwater and snowmelt drain from the windshield cowl, sunroof channels, and door drains; after rain or a car wash you may see clear water released under the car.
5
Washer fluid leak (looks like water)
A cracked windshield washer reservoir or hose leaks thin, often slightly blue or colored fluid that can be mistaken for water; check whether your washer fluid level is dropping.
6
Coolant or A/C leak inside the cabin (the rare concern)
If the 'water' is colored, sweet-smelling, or oily, or if you find dampness on the interior carpet, it may actually be coolant (heater core) rather than condensation and should be checked.

What to do

In most cases this needs nothing at all - if the fluid is clear, odorless, and appears only after running the A/C or in damp weather, it's just condensation. To be sure, dab the puddle with a paper towel: clear and watery is fine, while green/orange/pink (coolant), red (transmission), or brown/black and oily means it's not water and needs attention. Only worry if you smell a sweet odor, find wet carpet inside the car, or see colored fluid - in those cases have it inspected.

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Common causes

A/C evaporator condensation (normal)

By far the most common cause. Running the A/C produces clear water that drains out under the passenger side near the firewall. A puddle the size of a dinner plate or smaller, especially on hot, humid days, is completely normal.

Exhaust condensation (normal)

Water is a byproduct of combustion. On cold starts or short trips you may see clear water dripping from the tailpipe or pooling at the rear - harmless and a sign the engine is running efficiently.

Heater/defroster condensation

Running the defroster or heater in cold, damp weather can also produce small amounts of condensation that drains outside the cabin.

Windshield cowl or sunroof drains

Rainwater and snowmelt drain from the windshield cowl, sunroof channels, and door drains; after rain or a car wash you may see clear water released under the car.

Washer fluid leak (looks like water)

A cracked windshield washer reservoir or hose leaks thin, often slightly blue or colored fluid that can be mistaken for water; check whether your washer fluid level is dropping.

Coolant or A/C leak inside the cabin (the rare concern)

If the 'water' is colored, sweet-smelling, or oily, or if you find dampness on the interior carpet, it may actually be coolant (heater core) rather than condensation and should be checked.

What to do