DIY troubleshooter · causes ranked by how often each turns out to be the problem, in our judgment (no dataset ranks them)
Water pools around the indoor unit, drips from the ceiling near the air handler, or the drain pan overflows. An AC pulls water out of humid air and sends it down a drain line, so in muggy weather a blocked line shows up within hours.
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
Simplified drawing, not to scale. Real systems vary: the indoor unit can sit in an attic or closet, the ducts can run in the attic or under the floor. Original illustration, not a photo.
Stock photo, not our work. Photo by Yusuf Çelik via Pexels.
How to checkFind the PVC drain line that leaves the indoor unit, usually ending outside near the condenser. Slime, algae, or a dripping pan under the coil means the line is backing up.
Typical repair costFree to check. If you hire a pro instead: Condensate drain line or pump: Median $600 (most $440–$1,000), 15 homeowner reports
How to checkShine a light under the coil. A rust-stained pan with standing water, or water on the floor while the drain line is clear, points to a rusted or cracked pan.
Typical repair costFree to check.
How to checkWater shows up after the system has run for hours or after it was off. A clogged filter drops airflow, the coil ices, and the ice melts faster than the pan drains.
Typical repair costFree to check.
How to checkA float switch is a small safety device in the drain pan that shuts the system off when the pan fills. If the system stopped cooling and there is water in the pan, the switch may be doing its job or may have failed.
Typical repair costCondensate drain line or pump: Median $600 (most $440–$1,000), 15 homeowner reports
How to checkRepeated icing with a clean filter and clean coil is a low-charge sign. It cannot be confirmed without gauges.
Typical repair costRefrigerant leak repair: Median $1,320 (most $800–$3,000), 32 homeowner reports; Refrigerant recharge: Median $690 (most $460–$1,200), 48 homeowner reports
Ranks are editorial, not measured. A price is what homeowners reported for that one part or job, not a quote for the cause on that row, and a cause can involve more than one part. Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
$190
Median pro diagnostic visit, from 62 homeowner reports
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
These checks need no tools beyond a screwdriver, a hose, or a vacuum. Do them in this order.
5 Condensate drain line, pan and float switch
5 Condensate drain line, pan and float switch
2 Air filter
The causes below are not DIY, and we give no repair steps for them. Each carries a specific danger.
Source: Stationary Refrigeration and Air Conditioning (Clean Air Act Section 608), 2026-09-30; retrieved 2026-09-30.
Do not jump or bypass a float switch. It is the device that stops the system before the pan overflows into your ceiling; wiring around it can turn a small leak into ceiling collapse and mold.
Stock photo, not our work. Photo by Alex Domínguez via Pexels.
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Counts: businesses with an active license and a city address in the Tampa Bay outer ring, from FL DBPR construction licensee extract (CONSTRUCTIONLICENSE_1.csv), retrieved 2026-10-05. A license says the state permits the work, not that the work is good.
A pro visit starts with a diagnostic fee. Homeowners reported: Median $190 (most $100–$290), 62 homeowner reports. The repairs behind the causes on this page:
Reported price, U.S. dollars
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
| Repair | Median | Most (middle half) | Reports |
|---|---|---|---|
| Condensate drain line or pump | $600 | $440–$1,000 | 15 |
| Refrigerant leak repair | $1,320 | $800–$3,000 | 32 |
| Refrigerant recharge | $690 | $460–$1,200 | 48 |
These are national prices. We do not have enough Tampa Bay outer ring reports to publish a local one.
See the AC repair cost guide and the AC replacement cost guide for every repair and job we have enough reports to price.
Source: HVACPro analysis of 1,611 homeowner-reported quotes and invoices in public Reddit posts dated 2025-01-01 to 2026-09-29. Each price is the median of the reports for that job, and "most" is the middle half of them (25th to 75th percentile). Homeowners reported these prices and we did not verify them.
No utility rebate applies to this repair. The programs on file pay for replacement equipment or a tune-up, not for a repair like this one.
Stock photo, not our work. Photo by ready made via Pexels.
Trane lists four main causes of a central AC leaking water indoors: a corroded, cracked, or debris-filled drain pan, a clogged condensate drain line, a frozen evaporator coil, and a problem with the outdoor condenser unit. The cooling cycle generates condensation, and the drain line and pan carry that water away from the indoor unit.
Regular filter changes help you avoid a frozen coil. ENERGY STAR notes that a plugged drain can cause water damage in the house.
Checked against: ENERGY STAR (EPA/DOE): Maintenance Checklist (heating and cooling); Trane: AC Leaking Water. Pages opened 2026-09-30.
Turn the AC off first. Remove the cap from the drain line and look for debris. Loosen it with a wire brush or pull it out with a wet/dry vacuum.
Pour in diluted vinegar or a cleaner made for PVC, let it sit for 30 minutes or longer, then flush the line with water and clean the drain pan. If the clog stays, call a technician, who will have the proper tools.
Checked against: Lennox: AC Drain Line Clogged? Here's What to Do. Pages opened 2026-09-30.
Turn it off and call for repair. Trane says continuing to run a leaking AC could damage the system.
Where a condensate overflow switch is installed, it shuts down the outdoor compressor, the condenser fan, and the indoor supply fan when it detects a potential overflow. EPA says water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth, so dry any wet area right away and keep the drain line clear.
Checked against: Trane: AC Leaking Water; Trane: Troubleshooting the HVAC Air Handler Overflow Switch; U.S. EPA: A Brief Guide to Mold, Moisture and Your Home. Pages opened 2026-09-30.