What size PEX to use....

Users who are viewing this thread

Nick--L

New Member
Messages
9
Reaction score
1
Points
3
Location
New York
I am going to be replacing old copper lines in a home. I currently have a 1" line entering the home and within a few feet, it gets reduced to 1/2. I will be installing PEX manifolds and am wondering if there is an advantage to maintain the 1" line to the input to the manifold. All of the manifolds I can find, are 1" copper with 3/4 pex inputs. If you have a 3/4 " pex fitting on a manifod, is there an advantage to use 1" Pex to that fitting, or did any "volume" advantage disappear with the reduction to the 3/4" input. Thanks for your help
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
A short length pipe or fitting reduction doesn't equate to a long length of the smaller pipe because of the venture effect...the fluid (air/water/whatever) will speed up through a short reduction and then return to it's 'normal' speed while only inducing a slight pressure loss. The cross sectional area ratio of 1":0.75" is 1.96:0.44, or over 4x as much area, and that relates to its volume capacity. 3/4" pex is smaller than 3/4" copper. Now, whether you'd need that volume, I don't know, but if you went with 1" pex and converted to 3/4" at the manifold, you'd minimize any friction losses along the way, and maximize your working pressure (not the static pressure, which would always stay the same). ON the hot side, it would also increase the time it would take to get hot water since the pipe would hold more that could have cooled off since the last use. You might want to consider a hot water recycling system...it can save wasting water and increase your overall comfort. If you insulate the pipes or tubing well, it is not a significant energy user.
 

Nick--L

New Member
Messages
9
Reaction score
1
Points
3
Location
New York
A short length pipe or fitting reduction doesn't equate to a long length of the smaller pipe because of the venture effect...the fluid (air/water/whatever) will speed up through a short reduction and then return to it's 'normal' speed while only inducing a slight pressure loss. The cross sectional area ratio of 1":0.75" is 1.96:0.44, or over 4x as much area, and that relates to its volume capacity. 3/4" pex is smaller than 3/4" copper. Now, whether you'd need that volume, I don't know, but if you went with 1" pex and converted to 3/4" at the manifold, you'd minimize any friction losses along the way, and maximize your working pressure (not the static pressure, which would always stay the same). ON the hot side, it would also increase the time it would take to get hot water since the pipe would hold more that could have cooled off since the last use. You might want to consider a hot water recycling system...it can save wasting water and increase your overall comfort. If you insulate the pipes or tubing well, it is not a significant energy user.
great answer, just what I was looking for......
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks