Welcome to Plbg.com
Thank you to all the plumbing professionals who offer their advice and expertise

Over 600,000 posts related to plumbing

Welcome to Plbg.com (aka: PlumbingForum.com) we are the most popular plumbing information sharing, advice, DIY and educational forum on the Web. Ask any toilet, sink, faucet, pump, water quality, and plumbing related questions. Please refrain from asking where to purchase a product, business, pricing, or legal questions, for contractor referrals, or any questions not related to plumbing. Keep all posts positive and no advertising. This site is free and made possible by:  

Post New
Log In
How to Show Images
Newest Subjects
 pex vs copper flow rate
Author: Anonymous User

I am considering replacement of my copper water supply lines (circa 1960's) with a PEX system before I close in my basement ceilings. My question has to do with flow rate and volume of pex vs copper. I note that the ID of the 3/4" copper fittings for connecting pex is not much greater than the ID of 1/2" copper tubing and significantly less than 3/4" copper. I am not a hydraulic engineer, but wouldn't this restrict the maximum flow rate and capacity of my water supply?

Post Reply

 Re: pex vs copper flow rate
Author: Dunbar (KY)

Sure would.

You need to upsize the piping to match the id of copper to be code acceptable for your plumbing system.

Post Reply

 Re: pex vs copper flow rate
Author: Scott D. Plumber (VA)

If your plumbing fixtures are the good old high flow type typical of the '60s, you will notice the flow differance!

Like Dunbar said, you will need to upsize your piping for PEX to avoid flow issues.

Also, limit your joints with the PEX. That is one of it's advantages. You can get it installed with very few joints, eliminating many leak opportunities and keeping your flow to a maximum.

You should have joints at the tees and at the wall penatrations, but other than that try to make your runs in one piece.

Also use good components that secure your stub outs and keep them straight. one of the things that gives PEX a bad name is shoddy instaltion that does not make the piping secure and attractive where visible. (It should not flop all around like a garden hose!)

Post Reply

 Re: pex vs copper flow rate
Author: hj (AZ)

Yes, except at low flow rates.

Post Reply

 Re: pex vs copper flow rate
Author: Uni R

The fittings are restrictive but not as much as you might be thinking. You have to remember that a 3/4" ID pipe with fittings that are only 1/4" ID will have significantly more flow than a straight 1/4" ID pipe. The fittings do restrict the flow but only while the water is having to go through the fitting. The key with PEX is to minimize the fittings. To properly calculate the flow restrictions you have to measure the flow restrictions per foot of the pipe by its length and add the flow restrictions for each fitting. Different layouts will give different results so it is tough to compare PEX to Cu that way.

Post Reply

Please note:
  • Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
  • Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
  • Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
  • Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.

Search for plumbing parts on our sponsor's site:

Special thanks to our sponsor:

Copyright© 2017 Plbg.com. All Rights Reserved.