A mini-split air handler in the corner of a room just below the ceiling with a vent installed

Mini-split heat pumps are permanently installed in the home to provide heating and cooling at the flick of a switch. Convenience is a significant selling point of these systems.

Their installation is more straightforward than central air because there is no need to install ductwork, which can be very disruptive.

Indoor head units (also known as air handlers) can be placed in the home where needed to provide comfort to a single room, a zone comprising multiple rooms, or even to heat and cool an entire house.

All mini-splits and air conditioners generate condensation during regular operation in the summer. The condensate is just water that precipitates from the air onto the evaporator coil in the air handler.

It drips off the coil and into the condensation pan at the bottom of the mini-split, but where does it go from there?

This article will discuss the key features of a mini-split condensate drain, how they should be installed, and problems to look out for.

How Does a Mini-Split Drain From The Wall or Ceiling?

Mini-splits have condensate drains that allow condensate water to drain from the unit, usually going down the wall. A gravity drain is preferred because there are no moving parts to wear out or go wrong, but sometimes a condensate pump is needed to pump the water up to a point from which it can drain freely.

The condensate drain is an essential part of any mini-split installation because, without it, you’ll have water leaking from the indoor unit and dripping down your walls or from your ceiling.

They are a simple piece of plumbing that is usually easy to install, but a few slip-ups can cause issues if you are not aware of them.

What Is a Mini-Split?

Let’s quickly consider the key components for a mini-split installation. They are:

  • An outdoor unit that contains the compressor and a condenser coil
  • One or more indoor units (air handlers or head units)
  • Linesets that carry refrigerant
  • Electrical cables that run between the outdoor and indoor units provide power to the indoor units and allow communication between the two
  • The condensate drain that carries the water away from the unit and out of the house

The linesets, electrical cables, and condensate drain are typically tied together and passed through a small (3-inch) hole in the wall before being routed down an external wall to where the outdoor unit is located.

A ductless mini-split compressor on the external wall of a home

These lines are often enclosed in conduits, such as “line hide,” which conceals them from view and protects them from weather and rodents with sharp teeth.

Are you interested in a heat pump hot water heater? These operate using the same principles as ductless mini-splits and can be an excellent option for providing hot water for your home. Read more about them here.

How to Drain a Mini-Split

When a mini-split operates in cooling mode during the summer, condensation forms on the evaporator coil on the indoor unit.

The condensate water then drips off the coil and into a drain pan, which catches the condensate and allows it to drain into the condensate drain. The pan is not designed to hold any water, just to catch it and convey it into the drain.

Mini-splits have the option to fit the drain on either side of the unit, which provides flexibility so you can attach it on the most accessible side.

In the most straightforward case, when the air handler inside the house is attached to an external wall, the condensate drain passes directly through the wall, is routed down the side of the house, and drips onto the ground where it seeps away.

A ductless mini-split condensate drain at the bottom of line near the compressor
Courtesy of Quality Heating and Sheet Metal Company, Inc.

We are not talking about large volumes of water here, so there is not necessarily a requirement to direct a condensate drain into your main drain, although this can be an option.

Always check the code requirements for your area to ensure you comply with any drainage requirements because these vary from place to place.

Avoiding Problems with a Mini-Split Condensate Drain

Make Sure Your Indoor Unit is Level

A mini-split is carefully designed to handle condensate that forms during operation.

 If it is not installed perfectly level, the water will not be able to drain in the way it should, so make sure your units are installed correctly.

Test the Condensate Drain

If your mini-split was installed during the winter and not adequately tested, you might not notice any problem during the heating season. However, when summer arrives, and you turn on cooling mode, you could find you have a leak.

This issue crops up surprisingly often, so make sure the drain is tested at installation to avoid problems later in the year.

Ensure the Drain Has the Correct Slope

Water flows downhill. We all learned this in elementary school, but it’s surprisingly easy to forget when handling drainage pipes in awkward spaces.

You must ensure at least a 1% slope all the way along the condensate drain. You could have condensate backing up into your unit with any less than this.

Sometimes condensate drains are held in place with clips and can sag between them where they are not supported. Sagging creates short sections where the water can sit instead of draining away, which can cause blockages and are best avoided.

A helpful installation tip is to drill the hole through the wall behind your air handler at a downward angle, which helps to ensure the pipes are angled down immediately behind the air handler and prevents problems right at the top of the drain. 

Insulate the Condensate Drain

The condensate drain can be cold enough to allow condensate to form on the outside of its wall, which can cause drips and damp patches on the ceiling below your drain.

A simple way to prevent this is to insulate your condensate drain and prevent warm, moist air from coming into contact with it.

Do I Need a Condensate Pump?

If it is possible to allow your mini-split to drain solely under gravity, you should go with that option. A gravity drain has no moving parts, consumes no energy, and makes no noise.

For simple installations, with an air handler mounted on an external wall, the condensate drain can usually be passed through the wall and run down the outside of the building with no problem whatsoever.

In certain circumstances, however, it’s just not possible to route the condensate drain to have the required slope along its entire length. In these situations, you can install a condensate pump.

A condensate pump is mounted inside the air handler unit and comprised of a small reservoir with a float switch inside connected to the pump. When the switch is activated, the pump kicks in and lifts the water to a height it can then drain, under gravity, outside the house.

Promo photo of a mini-split's condensate pump
Courtesy of Power Equipment Direct

It’s a simple device but should only be used when absolutely necessary. Sometimes condensate drains can fail, causing leaks, and some of them can be a little noisy, which can cause a nuisance.

It will add to the overall cost of your installation as well.

We recently heard of a customer who quoted two different companies to install a mini-split. One company said he needed a condensate pump fitted, which would cost an extra $450. 

He didn’t need it. Of course, that company was just trying to make more money from him, so watch out for that practice and constantly question whether a condensate pump is required for your installation.

For more information about the cost of ductless mini-splits, you can read our article about that subject here.

Summary

Mini-splits produce condensate during regular operation in the summer months.

The condensate is taken away by the condensate drain attached to the back of the air handler inside the house.

The drain ensures the condensate water is removed from the system and discharged safely outside the home. Code requirements for drainage vary across the country, so check what the requirements are for your area.

A gravity drain is always preferred, but sometimes this is not possible, and a condensate pump needs to be fitted to pump the water up to a higher level from which it can then drain under gravity.

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