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Is It Normal for a Bathroom Fan to Drip Water?

It can be really annoying to constantly find small puddles of water in your bathroom or to see spots and stains on your walls and ceiling. Isn’t the fan supposed to be keeping moisture levels under control in the bathroom?

Well, yes, but it’s because they move moisture out of the house that they are prone to this issue. There are so many reasons why a bathroom fan would drip. Let’s look at them, how to remedy them, and, of course, answer your question about whether or not it’s normal for bathroom fans to drip.


While there are myriad reasons why bathroom fans drip water, it is not normal. It indicates a problem with the exhaust system. Each problem has a relatively simple solution.

Bathroom Fan Dripping: Common but Not Normal

As I mentioned, there are so many reasons why bathroom fans drip water, and this makes it a really common domestic problem. However, just because something is frequently happening does not necessarily mean that it is a normal occurrence and you should not worry about it.

Causes of Dripping Bathroom Fans

Bathroom fans drip water from the indoor vent as a result of condensation occurring in the ducts or water entering the ducts from outside.

Causes of Dripping Bathroom Fans Infographic: No or Poor Duct Insulation,  Overly Long or Twisty Duct Runs, Broken Ducts, Underpowered Fans, Broken Roof Vent Hoods or Flashing Problems, Broken Roof Vent Hoods or Flashing Problems and Broken/Missing Backdraft Damper

No or Poor Duct Insulation

If you do not have duct insulation or the insulation that you do have is insufficient, then you are more likely to struggle with a dripping bathroom fan, particularly if the duct runs through unconditioned spaces (although it must be insulated here).

The air that passes through the ducts from the bathroom is warmer than the air that surrounds the ducts. The heat is transferred out of the duct, down the temperature gradient.

As the air in the duct gets colder, its ability to carry moisture reduces and water condenses out to drip from your bathroom fan.

Overly Long or Twisty Duct Runs

Your fan may be dripping condensed water because of the composition and length of your ductwork.

Ducts that travel over a longer distance or are comprised of multiple joins and bends are less efficient at exhausting moisture-laden air to the outside of the house.

This is because the air will only be able to travel so far or be redirected at bends so many times before it loses too much energy and stagnates.

The air can then cool inside the duct and the condensation can drip and run through the ductwork, making a noise and causing issues at the fan’s interior vent.

Broken Ducts

Another reason that condensation is dripping from the bathroom fan may be that the ductwork itself is broken or contains imperfections that affect the rate and efficiency at which the air flows through them.

If there are holes or breaks within the ductwork, then the warm air can easily slip through the cracks, reducing velocity pressure inside the ducts.

As the air moves slower, it has more time to cool inside the ducts, causing the moisture in the air to condense and drip out of the fan vent.

Underpowered Fans

If your ductwork is perfect but your fan is underpowered, then it will not be able to get rid of all the moisture in the bathroom and the fan can drip.

While the fan itself may be functioning, the motor may simply not be strong enough to handle the amount of moisture that is being created in the bathroom, and so it is not expelling it as quickly or efficiently as needed to prevent condensation.

If this is the reason, you will also notice other signs, like steam hanging around in the bathroom for a good while after you shower, even if the fan is on.

Broken Roof Vent Hoods or Flashing Problems

You may notice that when it is raining outside, it appears to be raining inside your bathroom too!

Man repairing roof ventilation hood

Your bathroom fan can drip during wetter weather if a part of your roof vent cover of the associated flashing is letting water into the ducts from where it can drip from your bathroom fan.

Now, these two pieces are supposed to prevent just such an occurrence, so if they are letting the rain in, then they are faulty or damaged, and you will have to inspect and repair or replace them.

Broken/Missing Backdraft Damper

Bathroom fans should ideally be equipped with a backdraft damper. This is a device that ensures air can exit the duct to the outside but air on the outside cannot enter or re-enter the duct.

If there is no backdraft damper or if the damper is damaged, then you can experience certain problems like cold drafts and dripping from your bathroom fan.

The reason why your fan is dripping as a result of a missing or broken damper is that the exhausted air can re-enter the duct. The more time it spends in the duct, the more likely it is to cool inside the duct to the point at which the water condenses out of the air and water will drip out of your fan.

Another cause or contributor is the fact that colder outside air is allowed to mix with the hot exhaust in the ducts. This make the exhausted air drop in temperature and the moisture it carries will condense out because cold air cannot hold as much water as warm air.

Should You Worry About the Dripping?

The amount of water that drips out of your bathroom fan is not likely to resemble a large leak or small waterfall.

While the small amount of water that comes out is unlikely to be an imminent threat, over time it can cause issues.

If your bathroom fan is not functioning as it should—whether it is due to its inability to handle the amount of steam in the bathroom or issues relating to the ductwork—then you are likely to see the consequences of poor bathroom ventilation.

One of the more serious issues that could result from continuous dripping is the production of mold in the bathroom.

Since mold requires warm, moist air to breed and grow, the area surrounding the fan can quickly become infested, which can bring along a variety of health issues for your family if not treated immediately.

The mold can also cause structural damage to your home, making the beams and other components weaker and brittle, easier to break.

Mold in bathroom walls

The water that drips can cause less serious, but deeply frustrating cosmetic damage. The paint on your walls and ceilings can discolor or peel, which can make your bathroom appear to be old and unhygienic.

To try to reduce these effects, you can run your bathroom fan for longer to get rid of all the steam, but this does come with its own consequences. The fan will be subjected to more wear and tear and you also have to pay to run it longer.

Sources

https://homeinspectorsecrets.com/bathroom-exhaust-fans/bathroom-exhaust-fan-leaking-when-it-rains/

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