Aircon Cassette Leak, Drain Sludge

Case Details

What We Checked

• Drain line was completely blocked — thick sludge had accumulated inside and no water was flowing out.
• Condensate was filling the pan and overflowing at the lowest corner, dripping down along the ceiling mount.
• After flushing the drain line clear with pressurised water, drainage resumed and the overflow stopped immediately.
• Pan surface was inspected after draining — no cracks, holes, or visible corrosion found on the pan body.

The Diagnosis

Fifteen years of use had allowed sludge to block the drain line. With no outlet, condensate filled the pan and overflowed at the lowest corner. The pan was intact — water was going over the edge, not through it.

What Fixed It

The drain line flush resolved the leak completely. No pan replacement or ceiling work was needed. The client was advised to include drain flushing in their regular servicing schedule to prevent future blockages in this older unit.

The dripping stopped immediately after the drain was flushed. The original pan and cassette unit remained in place. No ceiling access or dismounting was required.

Why This Happens

Cassette drips — blocked drain vs cracked pan in older units.

• A cracked pan lets water seep through the pan body even when the drain flows. A blocked drain forces water over the pan edges. Both cause dripping, but the overflow pattern and drip point differ.
• In older commercial cassette units, sludge builds up in the drain line over years of use. The warm, damp interior is ideal for growth. Regular drain flushing prevents this.
• Flush the drain before recommending any pan work. If the dripping stops and the pan shows no cracks, the drain was the cause, not the pan.