Staining on the ceiling of a room directly beneath an attic HVAC unit, with the roof sound above, most likely traces to:

When an air handler sits in an attic, it manufactures water. The cooling coil condenses moisture out of the air continuously during the cooling season, and that water has to be captured in a primary pan, carried away by a drain line, and caught by a secondary pan if the primary fails. Each of those is a common failure point: the drain line clogs with biological growth, the pan corrodes through, the trap dries or is missing so the line will not flow, or the secondary pan's own drain is blocked. When any of them fails, the water lands on the ceiling directly below the unit — which is exactly where the staining in this scenario is. The roof being sound is what completes the diagnosis by eliminating the other overhead water source, so the report points at the condensate system and recommends HVAC evaluation rather than roofing.

An attic air handler produces condensate continuously in cooling season, and the pan, drain line, trap and secondary pan are all common failure points. Staining directly beneath the unit with a sound roof above points at that system.

Air handlers in attics require a primary condensate drain with a properly configured trap and a secondary pan with its own drain or a safety switch. Clogged lines, corroded pans and improper traps are frequent causes of ceiling damage below.

The Unit Makes Its Own Water. When the ceiling under an attic air handler stains and the roof is sound, look at the pan and the drain, not the shingles.

Check for a secondary pan and a float safety switch. Their absence is a separate reportable deficiency and explains why a failure reached the ceiling at all.

• •Assuming any ceiling stain means a roof leak
• •Missing an absent or non-functioning secondary pan and float switch
• •Overlooking a dry or improperly configured condensate trap