Still on my quest for improving flow rate, I decided to visit my local Big-R today and to my suprise they carried WAY more stuff that Home Depot.
I even found these little 5/8" fitting gems. I wasn't sure if 1/2" tubing would fit over them, but I decide to buy them anyway. Once I got home I tried it out...not only does 1/2" go over them, my 7/16"ID5/8"OD tygon 3603 also fits and that with just normal pressure, no special heating or anything.
In addition I see that the 3/8"NPT (Threaded) to 1/2" fittings have a nasty step on the inside and these 5/8" fittings are smooth all the way through.
I also measure the ID of the fitting and found that
1/2" Barbs ID = 3/8"+ or maybe 13/32"
5/8" Barbs ID = 7/16"+ or mabye 15/32"
So 5/8" fittings should be quite a bit less restrictive, not only in size, but they don't have a step on the inside like the typical 1/2 barbs do.
Here are the pics:

7/16" ID Tygon fits no problem:

Check out the free flowing 5/8" left and step down 1/2" right:

5/8" barb ID measured:

1/2" barb ID measured:

Anyhow, probably not going to make some miraculous difference, but why use 1/2" ID tubing and 3/8" ID fittings?
Every little bit counts, and if you're already buying the fittings, might as well go big
I even found these little 5/8" fitting gems. I wasn't sure if 1/2" tubing would fit over them, but I decide to buy them anyway. Once I got home I tried it out...not only does 1/2" go over them, my 7/16"ID5/8"OD tygon 3603 also fits and that with just normal pressure, no special heating or anything.
In addition I see that the 3/8"NPT (Threaded) to 1/2" fittings have a nasty step on the inside and these 5/8" fittings are smooth all the way through.
I also measure the ID of the fitting and found that
1/2" Barbs ID = 3/8"+ or maybe 13/32"
5/8" Barbs ID = 7/16"+ or mabye 15/32"
So 5/8" fittings should be quite a bit less restrictive, not only in size, but they don't have a step on the inside like the typical 1/2 barbs do.
Here are the pics:

7/16" ID Tygon fits no problem:

Check out the free flowing 5/8" left and step down 1/2" right:

5/8" barb ID measured:

1/2" barb ID measured:

Anyhow, probably not going to make some miraculous difference, but why use 1/2" ID tubing and 3/8" ID fittings?
Every little bit counts, and if you're already buying the fittings, might as well go big












