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Air conditioning installation advice: when to use a drain pump

Air conditioning installation advice: when to use a drain pump


If you’ve never heard of a drain pump being fitted during an air conditioning installation, you’re not alone.

In the majority of Commercial Air Conditioning and Home Air Conditioning installations, a drain pump is not necessary; gravity does the trick and the excess water simply flows down the conduit and empties outside.

HOWEVER, where a gravity drain isn’t appropriate, they are a very important part of an air conditioning installation, and it is important that a good quality unit is selected for the job.

Let’s dig in and explain:

  • What they do
  • How they work and
  • When you need one

What does a drain pump do?

You might be wondering where the water that drains from your air conditioning comes from in the first place?

Well, it actually comes from the air.

In the cooling process, the air con draws all the hot, humid moisture out of the air via the evaporator coil, and the condensed water is a waste product of the process.

From there, the water has to be disposed of, and that means getting it to the nearest drain.

Gravity, where water simply runs down the pipe, is obviously the preferred method. It is totally simple and absolutely foolproof.

However, in some air conditioning installations, the water has to go UP before it can go DOWN and that’s when you’ll need a drain pump, also known as an air conditioning condensate pump.

How an Air Conditioner Drain Pump works.

  1. Moisture laden warm air flows across the air conditioner’s cooling coil. As the air cools, this moisture condenses.
  2. The moisture slowly drips into a collector tray inside the air conditioner.
  3. The collected condensate (water) flows from the collector tray into a drain opening and downwards in a pipe or tube to the air conditioning drain pump.
  4. The air conditioner drain pump incorporates a small water reservoir which collects the condensate. A float switch located there is lifted by the rising water.
  5. When the water level inside the drain pump is near capacity, the float switch triggers a small electric motor.
  6. The motor pumps the water up and out of the reservoir to a drainage pipe or flexible tube.
  7. The drain pump pushes the condensate to an external building drain, where it is disposed of as wastewater.

Which air conditioner installations require a drain pump?

Any air conditioning system which requires the drain piping to go to a higher point than the internal unit will require a drain pump.

After all, water can’t flow uphill.

For example, a condensate pump will be required if the air conditioning unit is housed in a building cavity, crawl space or basement where the water cannot be drained away by gravity.

The other situation where a drain pump is needed is when the piping runs along a flat surface such as inside a ceiling, before dropping down a wall.

This is the  cassette air conditioners – which are becoming more and more popular with schools, hotels, restaurants, clubs, offices and retail outlets throughout South East Queensland.

For this reason, the majority of cassette air conditioners come with a condensate pump built in, although some don’t — and it pays to check.

Sometimes, a pump is needed with ducted air conditioning systems, (MHIAA Ducted air conditioners have pumps built in as standard, this allows them to be hung lower in the ceiling if necessary ), and high wall split systems, because it’s physically impossible to run the piping straight to the drain due to adjoining internal walls and ceilings/ floors.

By the way, if you’d like to get a better understanding of the different types of air conditioner, and which would be best for you, we recommend you read our FREE guide…

Which type of drain pump for your air conditioning installation?

Like everything in life, not all condensate pumps are the same. Some of the cheaper models can be:

  • Noisy
  • Prone to failure
  • Difficult to maintain.

For this reason, we will only supply a high-quality unit that is designed to give years of trouble-free life.

This last point, (difficult to maintain) is something that is often overlooked, but can be very important.

Here’s why…

Drain pumps contain a filter screen — to keep bugs and debris out so the pipe doesn’t get blocked; if it does, then there may be ensuing water damage.

A service mechanic must be able to clean, wash the screen and other components to keep the pump pristine and in top working order. It only takes a few minutes. But regular servicing is very important, as you’ll read in a moment.

And by the way, another thing that is tied in with the issue of maintenance is the location of the pump.

Some pumps can be installed behind the air conditioner.

On one hand, they are neat and out of the way.

On the other hand, they can be “out of sight, out of mind”, and if your service technician isn’t on the ball, problems can occur.

To explain…

We’ve seen situations where an air conditioning service technician has just done a cheap ‘tick and flick’ maintenance call, (Please note: Acer Services do NOT do this type of maintenance!), didn’t properly disassemble the unit and didn’t see the pump was there.

They therefore haven’t cleaned the filter during the service call, with disastrous consequences down the track when it clogged up and water could no longer escape to the drain.

The rule of thumb is: external is better as they are easier to clean and maintain.

A word about bedroom air conditioner installations.

In our experience, it’s wise to avoid putting pumps on bedroom air conditioners if you can, as they can become quite noisy as they start up and shut down.

This is one of the things we will look at for you when we discuss your bedroom air conditioner installation. If possible, we’ll find a location for your high wall split air conditioner that:

  • Circulates the air really well.
  • Is easy to access for maintenance.
  • Looks good in the room.
  • Doesn’t require a drain pump.

This isn’t always possible in all situations. But we do our best to achieve it for you as we really want you to enjoy many happy hours of undisturbed sleep!

Like to know more about drain pumps, or air conditioner installations generally?

For more information about anything to do with Home Air Conditioning or Commercial Air Conditioning, speak to the friendly, ever-helpful team at Acer Services.

Simply click here to contact us.