How to Clean a Heat Pump

How to Clean a Heat Pump (how I clean my Vaillant Arotherm)

A heat pump sits outside in all weathers and takes the full hit from the elements. Wind, rain, snow, dirt. If you’re near the coast, you’ve also got salt in the air.

Over time, that shows, especially on the outside casing.

In the same way you’d wash your car to protect the paint and stop it looking tired, I think it makes sense to do the same for your heat pump. It’s sitting in your garden after all, so you want it looking half decent.

This article is part of my wider series of Vaillant Arotherm guides, aiming to demystify the settings that matter most for efficiency and comfort.

Why I bother cleaning it

The casing on my Vaillant aroTHERM plus is white, and it doesn’t stay that way for long.

If I don’t clean it regularly I get:

• Dark water streaks down the front
• General grime buildup
• Dirt collecting in the circular front vents

None of this affects performance directly, but it makes the unit look older than it is. And if you’re like me, that starts to annoy you.

What I use (simple and cheap)

After a bit of trial and error over the last 4 winters, I’ve settled on something very simple:

• Car wash shampoo
• Sponge
• Microfibre cloth
• Bucket of warm water

Nothing specialist. Just the same stuff I use on the car.

My cleaning process

It’s basically a car wash, just smaller.

1. Initial rinse
   Get the loose dirt off with cold water and a cloth.
2. Wash
   Warm water + car shampoo + sponge.
   Same approach as washing a car panel.
3. Rinse
   Cold water again to clear everything off.
4. Dry
   Microfibre cloth to avoid streaks and water marks.

Optional: a bit of protection

If I’ve got some to hand, I’ll apply a neutral car wax.

It adds a light protective layer so water beads off rather than sticking. That helps slow down those dark streaks coming back.

Not essential, but it does make a difference over winter.

Alternative people recommend

Some people in the Vaillant Arotherm Facebook Group recommend ACF-50 as a cleaner and protectant.

I’ve not used it myself, so I’ll leave that as a “worth looking into” rather than a recommendation.

While you’re there… check airflow

Every time I clean the front, I also have a quick look around the back.

• Clear out any leaves or debris
• Make sure airflow isn’t blocked
• Check the coil isn’t clogged

This part actually does matter for performance.

Cleaning around the heat pump

It’s not just the unit itself. The area around it matters as well.

I find all sorts builds up underneath and around mine over time:

• Leaves
• Bits of litter
• Weeds growing through the gravel

So whenever I’m cleaning the unit, I give the surrounding area a quick tidy as well.

It only takes a couple of minutes, but it keeps airflow clear and stops debris getting pulled back into the unit.

I also check:

• The base isn’t clogged up
• Water is draining properly
• The soakaway or drain area looks clear

If water can’t drain away, you’re more likely to get pooling or ice in winter, which is something you want to avoid.

What I don’t do

• No pressure washer
• No harsh chemicals
• No dismantling panels

This is just a light clean and tidy, not a service.

I leave the full strip down and clean to the professionals at the heat pumps annual service.

My take after 4 years

This is one of those low-effort jobs that keeps things looking good and avoids buildup getting out of hand.

It won’t transform your COP overnight, but:

• It keeps airflow clear
• It could avoid unnecessary noise
• And it stops the unit looking like it’s been neglected

I think you should treat it like you would your car.

A quick clean a few times a year keeps your Vaillant aroTHERM plus heat pump looking decent and running as it should.