AC Unit Dripping Water? Here’s What You Should Do

Is that puddle under your air conditioner just normal condensation, or is it an early warning sign of a bigger problem? Many business owners and homeowners panic when they see water around their air conditioning unit, but not all moisture indicates a serious fault.

When your air conditioner starts dripping water where it should not, it can be both puzzling and worrying. Water in the wrong place can damage walls, ceilings, floors, and even the air conditioning equipment itself. The good news is that most AC water leaks are caused by a small number of common issues that can often be resolved quickly once you know what to look for.

Quick summary: what to do if your AC unit is dripping water

• Turn the system off at the thermostat and at the electrical isolator or consumer unit.
• Check for obvious blockages or kinks at the condensate drain outlet pipe.
• Replace or clean the air filter to restore airflow and reduce the risk of coil freezing.
• Do not attempt to work on refrigerant circuits or internal electrics yourself – this must be done by an F-gas certified engineer or company in the UK.
• If you are in Bristol or the South West, arrange a visit from a local specialist such as Controlled Climate Ltd to diagnose and repair the problem.

In this practical guide, you will learn how to tell normal condensation from problematic leaks, understand the most common causes of dripping AC units, and follow clear steps to deal with them safely. We will also cover when it is time to call in a professional and how regular maintenance helps prevent future water issues.

Why Water Leaks Occur

Your air conditioner naturally produces condensation as part of the cooling process. As warm, humid air passes over the cold evaporator coil, moisture in the air condenses into water droplets. In a correctly installed and maintained system, this water collects in a drain pan and then flows away through a condensate drain line to a suitable discharge point.

A small amount of water around the outdoor unit is usually normal, especially in warm, humid conditions. However, water pooling inside your property, running down walls, or dripping from the indoor unit signals a problem. The difference between normal condensation and a leak often comes down to where the water appears, how much you can see, and how long it has been present.

Most internal leaks occur because something has interfered with the normal drainage path. Blocked condensate lines, frozen evaporator coils, damaged drain pans, or poorly secured pipework can all turn normal condensation into a problematic leak that needs attention.

Spotting the Warning Signs

Early detection of AC water leaks can prevent costly damage. Watch for these warning signs around your system:

What starts as a small drip can quickly escalate. Even minor leaks can damage plasterboard, flooring, and insulation over time. Persistent moisture also creates ideal conditions for mould and mildew, which can affect indoor air quality and require specialist remediation if left unchecked.

Common Causes of a Dripping AC

Clogged Condensate Drain Line

The most frequent cause of AC water leaks is a blocked condensate drain line. This pipe carries condensation from the indoor unit to a safe drainage point outside or to a suitable internal drain.

Over time, dust, dirt, and microbial growth, such as algae, can build up inside this line. The warm, moist environment of the condensate pipe makes it an ideal place for sludge and biofilm to form. As this builds up, water flow slows and can eventually stop altogether.

When the drain line blocks, water backs up and overflows from the drain pan. You may see water around the indoor unit, damp patches below an attic or ceiling cassette, or staining around a cupboard where the air handler is located.

To reduce the risk of this issue, many manufacturers and engineers recommend periodically flushing the drain line with a small amount of white vinegar. This mild acid helps to break down organic build-up and keep the line flowing. Only carry this out where you can access the correct cleaning point safely and without removing sealed covers.

Frozen Evaporator Coil

When your AC’s evaporator coil freezes, it creates a secondary water problem. Ice forms on the coil when:

• Airflow is restricted (often due to a dirty or blocked air filter)
• Refrigerant levels are low because of a leak or fault (engineer’s job only)
• The blower fan is not running correctly

As ice builds up on the coil, airflow is restricted even more, making the issue worse. When the system is switched off or the ice melts for any reason, a large volume of water can suddenly be released into the drain pan. If the pan or drain line cannot cope, it will overflow.

Typical signs include the indoor unit blowing warm air or reduced airflow, followed later by water appearing around the unit. You may see frost on the refrigerant lines or hear water running into the drain pan when the unit shuts down. Any suspected refrigerant issue must be checked and repaired by an appropriately qualified, F-gas certified engineer.

Damaged Drain Pan

The drain pan sits beneath the evaporator coil and collects condensation before it flows away. In older systems, metal pans can corrode. In newer or compact systems, plastic pans can crack due to age, impact, or stress.

Look for these signs of drain pan damage:

• Visible rust spots, pinholes, or corrosion
• Cracks or splits in the plastic sections of the pan
• Water dripping from under the unit rather than through the drain outlet

A damaged drain pan allows water to escape before it reaches the drain line, leading to drips in places you would not normally expect. A careful visual inspection with a torch is often enough to confirm whether the pan is intact or has started to fail.

Loose or Disconnected Drain Pipe

The constant vibration of an air conditioning system can gradually loosen mechanical joints. This is particularly common where the condensate drain pipe connects to the drain pan or where push-fit fittings have been used.

If these connections become loose, water can leak from the joint rather than being carried away. You might see water around the connection point or notice that the drain pipe has slipped or sagged.

Check that all visible fittings are secure and properly supported. Condensate drain pipes should be correctly graded, firmly connected, and sealed to prevent future disconnections. Any changes to the routing or termination of a condensate drain should follow the manufacturer’s instructions and local building practice.

Quick Troubleshooting Steps

Switch Off the AC

Before attempting any checks, turn off your AC at the thermostat and isolate the power at the consumer unit or local isolator. This protects you from electrical hazards and prevents further water build-up while you investigate.

If your AC is leaking a noticeable amount of water, do not continue to run it. Operating a leaking unit can lead to electrical short circuits, damage to electronic controls, and more extensive water damage to your property.

Replace or Clean Your Filter

A dirty or blocked air filter is a very common contributor to AC leaks. When airflow is restricted, the evaporator coil can become too cold and freeze, leading to water overflow when the ice melts.

Locate your system’s air filter and check its condition. If it looks dirty or clogged, replace it with a suitable new filter or clean it if it is the washable type, following the manufacturer’s guidance. Restoring correct airflow often prevents coil freeze-ups and can resolve minor leaks.

As a general rule, filters should be checked regularly and replaced every 1-3 months during heavy use. Properties with pets, higher dust levels, or commercial usage may require more frequent changes. A planned air conditioning service and maintenance visit is a good opportunity to confirm that the correct filter type is being used.

Clear the Condensate Drain

Clearing a clogged condensate drain line is often an effective fix for a leaking indoor unit, provided it can be done safely and without dismantling sealed components:

To test whether the drain is clear, slowly pour clean water into the access point and ask someone to check that it flows out of the external drain line without backing up. If the line remains blocked or you cannot safely access it, stop and arrange a visit from a qualified engineer.

Inspect for Visible Damage

With the power safely isolated, you can carry out some basic visual checks:

• Use a torch to inspect the drain pan for cracks, corrosion, or standing water.
• Check that the condensate drain pipe is firmly connected to the drain pan spigot.
• Look for obvious gaps, sagging pipe runs, or joints that appear loose.
• Confirm that the indoor unit is level and securely mounted, as a badly pitched unit can cause the pan to overflow at one side.

Minor cracks in an accessible drain pan can sometimes be temporarily sealed with an appropriate silicone or epoxy product, but this should be treated as a short-term measure only. In most cases, a damaged pan should be replaced by a professional as part of a longer-term repair.

IMPORTANT DISCLAIMER: The troubleshooting steps above are general guidance only. Always refer to your specific AC manufacturer’s instructions before attempting any maintenance, and never remove covers that protect electrical components or refrigerant pipework. Work on refrigerant systems in the UK must be carried out by an appropriately qualified, F-gas certified engineer or company. If you are unsure about any step, we recommend contacting a qualified professional rather than attempting further DIY.

When to Call a Professional

While straightforward issues such as a blocked condensate outlet may be resolved with simple checks, many AC water leak problems require professional attention, especially in commercial or multi-unit systems.

If your AC continues to leak after you have cleaned the drain outlet and replaced the filter, there may be a deeper fault that cannot be safely diagnosed without specialist tools. A professional engineer should check for the following:

• Low refrigerant charge or refrigerant leaks (requires specialist equipment and F-gas certification)
• Faulty condensate pump on systems where water is pumped to a higher-level drain
• Internal component damage, such as cracked pans within cassette units
• Electrical or control faults that prevent correct operation or a safety shutdown

You should also contact a professional promptly if you notice:

• Repeated leaks after you have carried out basic cleaning and checks
• Water-soaked insulation, swollen skirting boards, or significant ceiling staining
• The AC turns on but does not cool properly, or trips on fault codes

Experienced HVAC engineers use specialist equipment such as nitrogen and dedicated cleaning tools to clear long condensate runs, accurately measure refrigerant pressures and temperatures, and confirm that the system is operating within manufacturer and UK regulatory limits.

For larger or commercial systems, regular inspections and leak checks are also a legal requirement where F-gases are present. You can find more details in the UK government’s guide to air conditioning inspections in buildings.

Preventive Measures to Avoid Recurring Drips

Regular Maintenance Checks

Preventing leaks is almost always easier and cheaper than repairing water damage. A simple maintenance routine can significantly reduce the risk of future condensate problems:

These simple tasks, combined with periodic professional servicing, are usually enough to prevent the most common causes of AC water leaks. For further practical tips, you can also review our air conditioning maintenance guide and our article on why you should service your air conditioner regularly.

Professional Tune-Ups

An annual professional service, carried out by an F-gas certified engineer or company, goes far beyond basic DIY checks and is strongly recommended for both home and commercial systems.

• Technicians clean indoor and outdoor coils correctly to maintain efficiency.
• They verify refrigerant levels and look for signs of possible leaks.
• They test electrical components, safety devices, and control settings.
• They flush or vacuum condensate drain lines and confirm that water is discharging properly.

A planned air conditioning service and maintenance visit helps to reduce running costs, extend equipment life, and keep you compliant with UK F-gas regulations where applicable. For businesses, regular servicing and leak checks are an important part of environmental, health and safety responsibilities.

If your system does not already have a float switch or similar safety device, ask your engineer whether one is suitable. These devices automatically shut down the system if water starts to back up in the drain pan, preventing overflow and limiting damage.

Monitor and Document

It is good practice to keep a simple record of how your system behaves and when maintenance is carried out:

• Listen for unusual sounds such as gurgling, dripping, or buzzing.
• Watch for changes in cooling performance, short cycling, or unexpected shutdowns.
• Note any signs of water, damp patches, or musty odours near units or ductwork.

Keep a log of filter changes, drain line cleaning, and professional service visits. This helps you stay on top of routine tasks and provides valuable information to engineers if you ever need fault-finding or a quotation for replacement equipment. If you are considering a system upgrade, you may also find our guide to choosing a home air conditioning system or our commercial air conditioning buying guide useful.

AC Leaking in Bristol or the South West?

If your AC unit is dripping water in Bristol, Bath, Weston-super-Mare, or elsewhere in the South West, it is important to address the issue quickly before it causes lasting damage. Local climate conditions, with periods of high humidity and mixed summer temperatures, can place extra demand on systems and increase condensate production.

Controlled Climate Ltd provides air conditioning services in Bristol and across the wider region, including fault-finding, leak repairs, and preventive maintenance for homes, offices, and commercial sites. Whether your problem is a blocked drain on a single split system or recurring leaks on a larger commercial installation, an experienced local team can diagnose the cause and advise on the safest, most cost-effective remedy.

We work across multiple sectors throughout the South West. From home air conditioning installations in bedrooms and loft conversions, through to office air conditioning systems and server room cooling, correctly designed drainage and regular servicing are always built into our approach. You can see more about our regional coverage on our South West air conditioning locations page.

Conclusion: Wrap-Up

A dripping AC unit usually indicates a problem within the condensate drainage system, but many causes are straightforward once identified. By understanding the typical reasons and acting promptly, you can often limit damage and keep your system operating safely.

• First, turn off your AC and isolate the power for safety.
• Check and replace or clean air filters to maintain good airflow.
• Inspect and, where safe, clear the condensate drain line.
• Look for visible signs of damage to the drain pan or pipework.
• Contact a qualified, F-gas certified engineer if the leak persists or you suspect a refrigerant or electrical fault.

Regular maintenance remains your best defence against AC water leaks. With sensible care and professional support, your air conditioning system can keep your space comfortable without causing unwanted indoor puddles or hidden damp patches.

Prompt action when you first notice a leak will almost always reduce the overall cost and disruption. Do not ignore even small drips – they are often your system’s way of telling you that something needs attention.

Need expert help with your AC issues?

At Controlled Climate Ltd, we have been providing trusted air conditioning services across Bristol, Bath, Weston-super-Mare, and surrounding South West areas for over 30 years. As REFCOM-accredited specialists, we ensure your system is inspected, repaired, and maintained to high technical and regulatory standards.

BOOK A FREE SURVEY or call us on 01174 528511 for emergency repairs, planned maintenance, or advice on upgrading older equipment.

FAQs (Frequently Asked Questions)

• What causes the water to drip from my AC unit?
  Your AC creates condensation as part of the cooling process. When the condensate drain line, drain pan, or pump becomes blocked, damaged, or incorrectly installed, this water can leak out instead of draining away safely.
• How can I tell if my AC condensate drain is clogged?
  Water pooling around your indoor unit, damp marks below a ceiling cassette, or gurgling noises from the unit can all indicate a partially or fully blocked drain. If your AC has a safety float switch, you might also notice it shutting off unexpectedly, even though the thermostat is calling for cooling.
• Should I run my AC if it’s leaking water?
  No. You should turn off your AC and isolate the power if it is leaking water. Continuing to run the system can cause electrical hazards, damage to internal components, and further damage to your property.
• How often should I clean my AC drain line?
  During the main cooling season, aim to clean or flush the condensate drain line every three months, or more often in very humid environments or where blockages have occurred before. This is often completed as part of a routine service visit.
• Why does my AC freeze up and then leak water?
  Freezing usually occurs when airflow is restricted (commonly due to a dirty filter or blocked return grille) or when there is a refrigerant problem. Once the ice on the coil melts, it can overwhelm the drain system and cause leaks. Any suspected refrigerant issue should only be checked by an F-gas certified engineer.
• Can I fix a cracked AC drain pan myself?
  You may be able to apply a temporary seal to a small, accessible crack using a suitable sealant, but this is not a long-term solution. In most cases, a damaged drain pan should be replaced by a professional to ensure safe and reliable operation.
• How can I prevent my AC from leaking in the future?
  Prevention focuses on good airflow and clean drainage: change filters regularly, keep return and supply grilles clear, have the condensate system checked and cleaned as part of annual servicing, and make sure any safety devices, such as float switches, are tested and working.
• Should I worry about a small amount of water under my outdoor AC unit?
  A small amount of water near the outdoor unit can be normal, particularly on humid days or after defrost cycles on heat pumps. However, water pooling inside your building, or dripping from indoor units, grilles, or pipework, always requires investigation.
• How long does it take to fix an AC water leak?
  Simple issues, such as a minor blockage at the drain outlet, can often be resolved in a relatively short visit. More complex problems, such as replacing a drain pan or dealing with restricted access to ceiling units, will take longer and may require additional parts and follow-up visits.
• Who is allowed to work on refrigerant leaks in the UK?
  In the UK, only appropriately qualified, F-gas certified engineers and companies are permitted to carry out work such as leak checking, refrigerant recovery, recharging systems, or altering pipework that contains F-gases. Property owners should always confirm certification before authorising this type of work.
• Can a leaking AC unit cause mould or health problems?
  Yes. Persistent damp around indoor units, ceilings, or ductwork can encourage mould growth and dust mite activity, which may aggravate allergies or respiratory conditions. Dealing with leaks quickly and keeping the system clean helps protect indoor air quality.
• Do I need planning permission to replace a leaking AC unit?
  In many domestic and light commercial situations, like-for-like replacement of external AC units will not require planning permission, but there are important exceptions, especially in conservation areas or listed buildings. Always check local rules or see our guidance on air conditioning planning permission in the UK if you are unsure.