Does one 6" flex = two 4" flex?

[ShannonRawls]

My bedroom is sized for a 6" run to a single 12"x6" register but I'd rather have two register vents for aesthetic/looks purposes. Will wye'g the single 6" to two 4" registers do the trick? What size will give me equal airflow?

[rimek]

"Does one 6" flex = two 4" flex?"

No

the sizing questions you have are all dependent upon system and duct design, duct length, room size, etc.
If you are building new, why not go with galvanized round instead of flex and use the 2 that you wish, with dampers properly installed by the trunk and balanced with the return? You are going to have return in this bedroom, no?

With all respect, this site is not for DIY.
In this case, you will lose money by NOT consulting with a professional.

Hint: 4" doesn't belong in a standard forced air system, except as flue pipe.

[Irishmist]

rimek, you shouldn't have even given the 'hint.' Now some idiot will try to vent their unit with 4" flex.

[propmanage]

Typical residential pressure drops 25’ flex .05"-.03"
90 degree elbows .02"-.06"
Start with identifying the volume of air you will be passing.
6” flex is designed for 75
5” flex is designed for 50
4” f?

[ShannonRawls]

Thanks friends,
I just left the HVAC company and they said don't bother splitting it using 4" flex. Instead the recommendation is split to two 5" flex with 10"x4" registers.

The ducting is already in place, I just rather have two good looking vents spead evenly on that wall instead of one big ugly one in the middle of it. I will use a 6x5x5 bullhead wye.

The return is a whole house return in the middle of the house.

I promise not to tell anyone the 4" secret. *smile*

[seatonheating]

This whole thread is a bunch of bologna. 4" can be used dependant on needs...that's all I'm going to say in this forum...sheesh.