Where Does the Water from a Caravan Air Conditioner Go?

Jul 12, 2025

Ever wonder if your caravan’s air con secretly cries from overwork? Short answer: it sweats! Caravan and Motorhome Air Conditioning pulls moisture from the air and drains it outside. But how it drains—and what could go wrong—is worth knowing. Stay dry, stay comfy, and let’s spill the (condensation) tea.

Understanding Condensation and Normal Operation

How Caravan Air Conditioners Create Water

Switching on your caravan’s air conditioner does more than cool the space—it kicks off a process that naturally creates water through condensation.

Warm, humid air from inside the van gets pulled into the unit. It then passes over a cold coil, which has been chilled by refrigerant. As the air cools, it hits its dew point. At this point, moisture in the air turns into liquid water.

The Role of the Evaporator Coil in Removing Humidity

The evaporator coil plays a key role in this process. As warm air moves over the coil, water vapour condenses on the surface and becomes liquid.

This helps lower the humidity inside your caravan, making the living space more comfortable. It’s especially effective in the UK’s damp climate. The cooler and more humid the air, the more water the system will extract.

Dometic roof-mounted caravan air conditioner on a white background.

How a Drain Pan and Weep Holes Work

The water formed by condensation drips into a drain pan located beneath the evaporator coil. From there, it’s directed towards small drainage holes, sometimes called weep holes.

These help guide the water out of the air conditioning unit. They prevent water pooling inside and keep the system running efficiently.

If these holes become blocked, however, water may back up and cause issues.

The Normal Drainage Process: Water on the Roof

In roof-mounted units, this drained water is typically released onto the roof. It can then drip down the sides of the caravan.

This is completely normal and not a sign of malfunction. In fact, spotting a bit of dripping during use can be reassuring—it means the system’s working as it should.

Different Types of Air Conditioners, Different Drainage

Rooftop Air Conditioners: The Most Common Drainage System

Rooftop air conditioning units are the standard in most UK caravans and motorhomes. These systems often come with internal piping to guide water outside.

They’re designed to let water drain directly down from the roof. This keeps the process simple and maintenance relatively low.

Still, occasional checks are wise to prevent buildup or clogging.

Under-Bunk/Ducted Systems: Internal vs. External Drains

Some caravans feature under-bunk or ducted units instead. These setups might use either internal holding tanks or external hoses.

With internal drains, you may need to empty the tank manually or use a pump system. External drains send water directly outside through hoses.

Knowing your setup is key to avoiding messes or blockages.

Portable Units: The Need for Manual Emptying

Portable air conditioners don’t have built-in drainage to the outside. Instead, they gather water in a removable reservoir or bucket.

This needs emptying regularly, especially in humid weather. Some models include an auto shut-off when full to prevent spills.

If you’re using a portable unit, build emptying it into your routine checks.

EcoFlow portable air conditioner with digital display and air vents, on a white background.

Troubleshooting Common Water-Related Issues

Why is My Air Conditioner Leaking Water Inside the Caravan?

Clogged Drain Holes: The Most Common Culprit

When drain holes are blocked by dust, debris, or algae, water can’t escape the way it should. It backs up into the system, often leading to internal leaks.

This is one of the most frequent causes of air con leakage inside caravans. Thankfully, it’s also one of the easiest to fix with regular cleaning.

A Damaged or Overflowing Drain Pan

If the drain pan is cracked, misaligned, or overwhelmed by too much moisture, water may leak out. Overflowing usually means there’s a downstream blockage or the water isn’t draining quickly enough.

Inspect the pan and drainage points if you notice dampness or puddles near your unit.

Incorrect Installation or a Worn Gasket

An air conditioner that’s not been installed properly can cause leaks. If the gasket (the seal between the unit and the roof) has worn down, water might sneak inside.

This is especially a concern during heavy rain or when the unit’s working overtime in humid conditions.

How to Prevent and Fix Water Leaks

Routine Maintenance: Cleaning Filters and Checking Drains

Preventing leaks is often as simple as keeping your air con clean. Regularly clean the filters to stop dust from clogging internal parts.

Also inspect hoses, drainage holes, and the pan. Look for signs of damage, algae, or blockages.

Clean and clear drains mean fewer leaks and longer-lasting equipment.

How to Safely Unclog Your Air Conditioner’s Drain

If you suspect a clog, disconnect the hose or find the access to your drainage line. Use a flexible brush, pipe cleaner, or even compressed air to gently remove debris.

Be cautious not to damage the line while doing so. Once cleared, flush with water to test flow.

When to Call a Professional for a Repair

Sometimes, problems go beyond what’s visible. If water keeps leaking despite your efforts, or if there’s structural damage, call a qualified technician.

They’ll check for internal faults, gasket issues, or poorly installed systems. A professional assessment can save you time and costly repairs later.

Woman using a Truma remote to control the ceiling-mounted caravan air conditioner in a wood-panelled interior.

Related Issues: Is It Condensation or a Roof Leak?

How to Differentiate Between AC Condensation and Rainwater

Condensation leaks usually happen while the air conditioner is running—or shortly after. If you only notice dripping during or after rain, you may have a roof leak.

Condensation tends to leave smaller, cleaner water trails. Roof leaks, on the other hand, may bring in dirt or leave water stains.

Inspecting Your Roof Seals for Potential Leaks

To rule out a roof issue, check the seals around your air conditioner. Look for cracks, gaps, or degraded rubber.

Even a small breach can allow rainwater in. Resealing or replacing the gasket may solve the problem if condensation isn’t the cause.

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