Why Water Enters from Below: The Underside Problem

When an enclosure fails an IPX5 or IPX6 test, the water is usually found at the bottom. Gravity explains most of it, but the design reasons are more specific.

Cable entries

Glands are often fitted with the cable entering from below, so water runs down the cable and pools at the gland. A gland tightened on the jacket rather than on the inner sheath lets water track along the conductors. Fit a drip loop, and specify glands with a proper seal on the cable sheath.

Drain and vent holes

A drain hole that works in still air becomes an inlet under a jet. If the design relies on drainage, the hole needs a labyrinth or a membrane that passes air but not water.

Condensation

Sealed enclosures that pass the water test can still fill with condensate over a season. A breather membrane equalises pressure without admitting liquid water, and is usually better than a fully sealed design in outdoor equipment.

Test orientation

Test in the mounted orientation, including any tilt, and aim at the underside deliberately. A test that only sprays the top and sides is not an IPX5 test, whatever the report says.

Related technical notes

• Nozzle Calibration: The Number That Decides the Test
• The Spray Nozzle Alternative for IPX3 and IPX4
• IP54 or IP65: Reading Both Digits Together