Cassette water leak traced to blocked drain, not cracked pan

What we found

Before assuming the pan had cracked, we checked whether the drain line was clear and whether the water was overflowing the pan or leaking through it.

• Drain line was completely blocked with thick sludge — no water was flowing out of the drain at all
• Condensate was backing up inside the pan and overflowing at the lowest edge
• After flushing the drain line clear, water drained freely and the overflow stopped immediately
• Drain pan surface was inspected — no cracks, fractures, or corrosion found on the pan body

The drain line had gradually blocked with biological sludge over years of operation. With no path for water to drain, condensate filled the pan and overflowed. The pan itself was structurally sound — the water was going over the pan, not through it.

What we did

A thorough drain line flush cleared the blockage and restored normal drainage. The drain pan did not need replacing. The client was advised to schedule regular drain maintenance to prevent sludge from building up again.

The leak stopped immediately after the drain line was flushed. The cassette unit continued operating with its original drain pan. No ceiling work or unit removal was needed.

What we learned

Cassette leaks — cracked pan vs blocked drain.

• A cracked drain pan leaks through the pan surface even when the drain line is clear. A blocked drain causes water to back up and overflow the pan edges. Both drip from the unit — but the fix is very different.
• Before condemning the drain pan, the drain line should be flushed and the pan surface inspected for cracks. If flushing restores drainage and no cracks are found, the pan was never the problem.
• Cassette units in older commercial spaces often develop drain blockages from sludge buildup. Regular drain flushing prevents this from escalating to a leak.