Why Is My AC Leaking Water? Common Causes and Repair Costs in Rochester, NY

Water pooling around an indoor air handler or furnace cabinet is one of the more common cooling-season service calls we take across Greater Rochester. It is also one of the most misdiagnosed, because the water usually appears somewhere other than where the fault is.

In most cases the cause is straightforward. A blocked condensate drain accounts for the majority of these calls, and it is a routine repair rather than a failed system. The more expensive causes exist, but they are the minority, and there are clear signs that separate one from the other.

This guide covers what produces the water, how to identify the cause from what you are seeing, what you can safely resolve yourself, what the repairs cost in the Rochester area, and the point at which the system should be looked at professionally.

Shut the System Down First

Before investigating, switch the cooling off at the thermostat. Set it to OFF rather than raising the temperature, and leave the fan on AUTO.

There are two reasons for this. If the leak originates from a frozen evaporator coil, continued operation builds further ice and places the compressor under load it was not designed to carry. That is the single most common way an inexpensive repair becomes a costly one. Separately, water travelling near the electrical section of the air handler should be dealt with on a de-energised system.

Standing water against drywall or subfloor becomes a secondary problem quickly. The EPA notes that mould growth can begin within 24 to 48 hours of materials becoming wet, so drying the affected area matters as much as fixing the leak.

Why an Air Conditioner Produces Water at All

Understanding this narrows the diagnosis considerably, because it establishes that the water is normal and only its route has changed.

Air conditioning performs two functions simultaneously. It lowers air temperature, and it removes moisture. Warm humid air passes across a cold evaporator coil and the moisture in that air condenses on the coil surface. On a humid Rochester afternoon a typical residential system removes somewhere between five and twenty gallons of water from the air in a day.

That condensate collects in a drain pan beneath the coil and leaves through a condensate drain line, normally white PVC, terminating at a floor drain, a condensate pump, or outside through the foundation wall.

The system therefore produces water continuously throughout the cooling season. A leak rarely indicates a new source of water. It indicates that the established drainage path has been interrupted, which is why the investigation should begin at the drain rather than the equipment.

Identifying the Cause From the Symptom

The pattern of the leak identifies the cause more reliably than its volume. The table below covers the six causes that account for nearly all residential condensate leaks.

What you are seeing	Most likely cause	Homeowner or technician
Steady leak at the base of the indoor unit, worse on humid days	Clogged condensate drain line	Homeowner
Intermittent leak, sudden volume after the system cycles off	Frozen evaporator coil	Both, see below
Consistent leak regardless of humidity, drain line running clear	Cracked or rusted drain pan	Technician
Leak appeared after unrelated work near the equipment	Disconnected or sagging drain line	Homeowner
Leak alongside reduced airflow at the vents	Restricted air filter causing coil freeze	Homeowner
Leak alongside poor cooling and ice on the copper lines	Low refrigerant charge	Technician

The first row accounts for the largest share. The drain line is dark, permanently damp and carries a slow flow of water all summer, which makes it a favourable environment for algae and biological slime. Dust drawn through the return adds to the deposit. Over one or two seasons the internal diameter reduces until the line blocks entirely and the pan overflows.

A refrigerant shortfall belongs in a different category to the others. Refrigerant is not consumed in normal operation, so a low charge means the circuit has a leak. Recharging without locating that leak returns the same fault the following season, usually with additional compressor wear in between.

Confirming a Frozen Evaporator Coil

This cause can be confirmed without opening the cabinet. Inspect the copper refrigerant lines where they enter the indoor unit. Frost or ice on the larger insulated line, or visible ice on the coil itself, confirms a freeze. Where the system is also failing to hold temperature, the underlying causes overlap almost entirely with those covered in our guide to an air conditioner that runs without cooling, and the diagnostic sequence is the same.

Do not attempt to chip the ice away or apply heat directly. Evaporator fins damage easily, and a punctured coil converts a service call into a coil replacement.

Why a Furnace Appears to Leak During Cooling Season

A recurring summer call describes a furnace leaking water in July while the heating is switched off.

In the majority of homes in this region the air conditioning has no separate indoor cabinet. The evaporator coil sits in a sheet metal enclosure directly on top of the furnace, sharing the same blower and ductwork. When that coil or its pan overflows, the water runs down the exterior of the furnace cabinet and collects at its base. The presentation is a leaking furnace. The cause is the cooling system above it.

The consequence is worth taking seriously. Water tracking down a furnace cabinet reaches the control board and the inducer motor, which is the mechanism by which an unresolved drain restriction in August becomes a no-heat call in November. That sequence is most common in the older housing stock we work in around Pittsford, Brighton and the city line, where equipment is frequently installed in confined basement corners and a slow leak can run for weeks before anyone notices it.

Water at the base of a furnace during cooling season should therefore be treated as an air conditioning drainage fault and resolved before the heating season begins.

Clearing a Blocked Condensate Drain Line

This is within reach of most homeowners with a wet dry vacuum and takes around twenty minutes.

Bleach should not be used for this. It is widely recommended online, and it corrodes metal drain pans and any soldered joints it contacts. Vinegar achieves the same result without the damage.

Repeating the vinegar flush each spring prevents recurrence. Clearing and treating the condensate line is a standard item within an annual AC tune-up, which is why homes on a maintenance schedule rarely generate this call at all.

Water at a Vent, a Window Unit or a Ceiling

Water appearing away from the equipment has different causes, and the location identifies which applies.

Where the water appears	Cause	Resolution
Dripping from a ceiling or wall register	Condensation forming on uninsulated ductwork in a hot attic or crawlspace	Insulate and seal the duct run
Staining on a ceiling below an attic air handler	Overflowing secondary drain pan, or a blocked secondary drain	Technician, the primary drain has already failed
Inside the room at a window unit	Unit mounted level or tilted inward instead of draining outward	Adjust the tilt, clear the base pan drain hole
Outside at the condenser on a humid day	Normal condensate discharge	No action required

The second row deserves particular attention. Where an air handler is installed in an attic or crawlspace, as it is in many of the ranch and split-level properties we service around Henrietta, the secondary pan is the last line of defence. Water reaching a ceiling from that position means the primary drain has already blocked and the backup is now full.

Repair Costs in the Rochester Area

Exact pricing depends on the cause and the equipment, and the cost is confirmed before any work begins. The ranges below are typical for this area.

Repair	Typical Rochester cost	Frequency
Diagnostic visit, credited against the repair	$95 – $175	Every call
Clearing a clogged condensate drain line	$125 – $250	Most common
Condensate pump replacement	$150 – $400	Occasional
Drain pan replacement	$250 – $600	Older systems
Refrigerant leak location and repair	$300 – $1,500	Less common
Evaporator coil replacement	$900 – $2,800	Least common

The distribution is the point worth noting. The most frequent cause is also the least expensive to resolve. Where a system is leaking but otherwise cooling normally, a quotation for coil replacement or full system replacement warrants a second opinion before proceeding, and the diagnostic sequence behind our AC repair pricing in Rochester, NY follows the same order of elimination set out above.

When the System Needs a Technician

We cover Victor, Pittsford, Fairport, Penfield, Honeoye Falls, Canandaigua, Farmington, Mendon, Brighton, Chili and Churchville, and carry the common condensate and control parts on the vehicles, so the majority of these calls are completed on the first visit.