Air-conditioning condensate drainage

In cooling and dehumidification modes, moisture in the room air condenses on the indoor heat exchanger. The indoor unit needs a route to a suitable discharge point.

The condensate drain is separate from the refrigerant pipework and electrical cable, even when they follow the same route through the wall.

Gravity drainage

A gravity drain carries condensate downwards from the indoor unit. It depends on a continuous fall and a suitable discharge point.

The manufacturer’s installation instructions set the drain-hose position, connection, insulation and test procedure for the exact indoor unit. There is no universal fall, hose diameter or trap detail that applies to every product and route.

Poorly arranged drainage can cause leaks, staining, damp or nuisance discharge.

Condensate pumps

A purpose-made condensate pump can lift water where a continuous gravity route is impractical.

Pump selection depends on the manufacturer’s head, application and installation limits.

Discharge position

The complete drainage arrangement includes the route, discharge point and whether water moves by gravity or through a condensate pump.

Outdoor-unit water

An outdoor unit can produce water during heating and defrost. This is separate from the condensate collected from indoor cooling and needs its own drainage assessment.

An indoor condensate pump does not deal with outdoor defrost water.

Related entries

• Air-conditioning indoor-unit types
• Air-conditioning maintenance and filters
• Air-conditioning planning and outdoor-unit siting
• Condensate drainage