Increasing the duct size of my bathroom fan outlet?


  #1  
Old 09-12-17, 08:35 AM
B
Member
Thread Starter
Join Date: Feb 2017
Location: USA
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Increasing the duct size of my bathroom fan outlet?

I have a new bathroom fan that I'm installing that is 70 CFM. It will only be in the water closet part of the bathroom as the bathroom already has a larger 150 CFM fan in it.

The 70 CFM fan has a 3 in. duct outlet. I was wanting to use insulated ducting to run to the outside of my house but can't find any locally and am not finding many options online either.

Am I ok in using a 3 inch to 4 inch duct increaser to attach a 4 inch duct to my fan or would I be causing some issues with the air movement?

The duct will be about 12 feet in length and will have a pretty strait shot venting out through an exterior wall.
 
  #2  
Old 09-12-17, 09:42 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,939
Received 3,951 Upvotes on 3,544 Posts
Increasing the size of the duct from 3" to 4" is ok.
Just check and make sure your fan has enough strength to open a 4" vent.
 
  #3  
Old 09-13-17, 12:25 PM
B
Member
Thread Starter
Join Date: Feb 2017
Location: USA
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Increasing exhaust fan duct size

I have a bathroom exhaust fan that has a 3 inch duct outlet. However, I would like to use a 4 inch insulated flexible duct.

Is there an adapter I can use to accomplish this or do I have to first use a short run of 3 inch duct and then use a 3-inch to 4-inch increaser?
 
  #4  
Old 09-13-17, 12:55 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,939
Received 3,951 Upvotes on 3,544 Posts
Threads combined...........

Not sure if there is an off the shelf adapter but you could use a short piece of 3" and 4" PVC with a reducer/coupler.

I see the depot sells a pre-made tin adapter. You could wrap it in insulation after connection.
4 in. To 3 in. Round Reducer-R4X3 - The Home Depot
 

Last edited by PJmax; 09-13-17 at 01:13 PM.
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: