Is Your Bathroom Exhaust Fan Leaking When It Rains? (What To Do)

Why Is The Bathroom Exhaust Fan Leaking When It Rains?

The most common reason a bathroom exhaust fan leaks when it rains is because the bath vent hose is in a vertical slope and exhausts on top of the roof. 

It's a good thing (and required by code) that it's venting to the outside, but the downside is that if it isn't installed properly with flashing or if the roof cover is cracked or defective, rain can leak through the bathroom vent.

Also, when cleaning a bathroom vent, a roof exit is the most difficult to deal with.

The phrase "out of sight, out of mind" comes into the picture. Since the ceiling bathroom exhaust fan terminates on top of the roof, it can be very difficult to keep a close eye on it.

You may be tempted to just vent your bathroom vent into the interior, but this is an even worse idea.

The moisture spewed into your attic of wall cavity may lead to mold growth, wood damage, and may attract termites. 

A Defective Roof Vent Cover

If the bathroom fan is dripping water when it rains, it means that the flashing or some part of the vent cover is allowing in water. It also may be that the damper (flap) is loose or missing --- and is allowing in water. 

In short, you will have to get someone onto the roof to fix it. I invite you to read my guide on how to install a bath vent through roof here.

When it rains, water is getting through the cover, and the water is traveling down the vent hose, and then it is exiting from your bathroom fan onto the floor.

Besides the roof, it is also possible (though unlikely) that your bathroom fan vent goes to the exterior vertical wall, and it may have just enough slope that water is still dripping through vent hose and into your bathroom.

How Do You Fix A Bathroom Vent Cover If It Is Leaking Water?

When you are inspecting the exterior bathroom vent cover, you want to look for any hairline cracks where water is getting through. Closely look along the edges of the vent cover.

It's also important to make sure that the asphalt shingles aren't damaged around the vent hood. The roofing shingles should be on top of the upper portion of the bathroom vent flange. I encourage you to also check out ALL our guides on bath fan installation and repair right here.

It's also a good idea to check the nails or screws where the bath vent cover was installed into the roof sheathing. Water may getting in through the nail heads and onto your bathroom vent.

When you are up on the roof, it is also important to check that the flap is working properly. If the vent flapper is stuck open or is missing, when there is heavy rain, water can easily enter into your vent cover, travel down the hose, and drip all the way down into your bathroom.

Should I Inspect For Water Damage From A Dripping Bathroom Exhaust Fan?

It's also a good idea to go into the attic, ceiling, or wall (depending on where you bathroom fan is venting) and look for any possible water damage.

If your bathroom vent goes to the roof --- according to the U.S. Department of Energy --- there are a number of signs of water intrusion through your roof and into your attic such as warped sheathing, mold, and wet insulation.

You may even have to replace some of the roof sheathing if the water leak has been going on for some time. It's also important to insulate bath fan vents going into the attic to stop condensation forming. You can read our full guide on bathroom fan condensation here.

When you are inspecting an area for water damage, you will want to look closely for any indications of mold or mildew.

An attic or ceiling cavity is a dark place where mold loves to grow, so when you add in a water source from heavy rain, you may have mold growing on the underside of the roof sheathing or the back of drywall. When released into the air, mold spores can travel all throughout the home.

I highly recommend going into the attic and to inspect the vent hose termination carefully with a high powered flashlight.

Should I Install A New Roof Vent Cover?

If your roof vent cover has some cracks, the flapper is not working, or is otherwise defective, it may be smarter just to replace the whole cover with a new unit.

Bathroom vent covers aren't meant to last forever, and they are pretty cheap to replace.

Of course, if you hire a qualified contractor to replace the vent cover, you will have to pay for labor --- probably in the $100 to $250 range just for labor depending on your market, and the details of the job.

Just replacing the cover will be cheaper than having to change the entire hose.

Should I Check My Ceiling For Damage?

If your leaking bathroom exhaust fan has been going on for some time, it may be a very good idea to remove the actual bathroom exhaust fan and check for damage in the ceiling cavity.

There may be damaged insulation, damaged drywall, damaged wood framing, and there may be mold growing. If you want to check for moisture damage, read our guide on how to use a moisture meter for more details.

To remove the bathroom exhaust fan, you will first have to remove the plastic cover by pulling it down, and squeezing the metal clips.

Before you unscrew and pull out the bathroom exhaust fan, you will want to unplug the unit (sometimes there is an actual plug behind the cover) or you should turn off the electricity at the breaker box.

Please do not get electrocuted!

Read Also: How To Vent A Bathroom Fan Into An Attic?

Once you have the power off, just remove any screws holding the bathroom fan in place in the ceiling. When the bathroom fan is removed, you can inspect the ceiling cavity with a flashlight to look for any damage or mold issues.

It is also important to oil your bathroom exhaust fan once a year and now is a great time to do it since it is removed. Check out our guide on oiling a bathroom fan here.

Of course, if the bathroom fan is on the upper level of your home, it may be easier just to go into the attic to do the inspection. Just be careful not compress (ruin) any of the insulation, and make sure that you step carefully and don't go through the drywall ceiling. Be cautious!

Read Also: How To Replace A Bathroom Exhaust Fan Without Attic Access?

What's The Bottom Line On A Leaking Bathroom Exhaust Fan During Rainstorms?

It's a pretty bad situation when you have water dripping from your bathroom fan during storms. The bathroom exhaust fan is supposed to remove moisture from your bathroom, not be source of actual water!

Luckily, there is usually a very simple reason for this which is that the vent exterior cover is simply broken or not sealed correctly. Or, heaven forbid, there is a leak somewhere else in your attic and it is leaking onto the bathroom vent hose (but it's unlikely).

Anyways, when your roof is dry, it's important for you or a contractor to get out there as quickly as possible and to carefully inspect the bathroom exhaust fan cover. It may need to be replaced.