Drip Pan Under the Attic Installed Air Conditioning Coil

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House attic heating / cooling system installations should include a protective drip pan underneath (plastic or metal tray positioned underneath the evaporator coil cabinet / compartment), to collect condensate water.

Evaporator coil will not be visible to you, because it’s hidden inside the metal duct or its own compartment, but it has a drip pan underneath. This is the main drip pan that catches condensate water, and discharges it through the attached pipe (min 3/4″ in diameter, and 1/8″/ft slope).

You should be able to see this condensate discharge pipe (or part of it), because pipe comes out of the air duct or coil compartment wall, and continues through or beyond the attic to some conspicuous location so you can occasionally inspect it. If you notice some dripping from under the coil compartment, it means that that the main drip pan needs attention.

Air conditioning coil drip pan condensate discharge pipe should not be connected directly to the waste or vent pipe.

Because this drain pipe might become clogged, secondary drip pan is required, with its own drain pipe, and safety / water detection sensor with cut-out switch – highly recommended (required in some jurisdictions). Water accumulating in the drip pan would activate safety switch, and turn off air conditioning system.

For some reason, installers forget that drip pan under the attic installed air conditioning coil, and you might end-up with damaged ceiling and costly repairs.