Author Topic: Copper to Pex  (Read 526 times)

Roboturner

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Copper to Pex
« on: August 10, 2017, 04:16:30 PM »
I'm going to swap out some copper pipes in our basement with Pex (the copper pipes are in the way and some connections are corroding). It will be a few short runs, keeping the existing copper in the walls and to the fixtures.

I understand that the nominal ID of pex is smaller than copper, so I have seen some folks suggest up-sizing when moving from copper to pex to maintain flowrate. My question is for short (<50' 10' runs) will it be necessary to up-size? i havent seen a lot of 1/2" copper to 3/4" Pex adapters. Also are there any tips or tricks to keep in mind? I know part of the appeal of pex is to do home-runs to a central manifold, but this project will be more geared towards replacing short runs of copper to get them out of the way.
« Last Edit: August 11, 2017, 08:17:35 AM by Roboturner »
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ixtap

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Re: Copper to Pex
« Reply #1 on: August 10, 2017, 04:34:16 PM »
Have you looked online? For our boat projects, we order all of our connectors online because our preferred brand is not available locally.

I am not sure that 50' is actually considered a short run, but it is more important to be aware of how many connections are coming off of each run. ie Are you making a run to the upstairs bathroom wherein the shower, sink and toilet will all be fed by it?


Papa bear

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Re: Copper to Pex
« Reply #2 on: August 10, 2017, 04:45:31 PM »
I have never heard of sizing up for pex and I've done a few houses, some new, some copper to pex retrofit.  I have never noticed any reduction in water flow. 

If I have access to the coupling, I usually use a push fitting. But if you are burying it, you need to solder on one of the brass barbs that the pex will crimp on to.

Good luck!


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paddedhat

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Re: Copper to Pex
« Reply #3 on: August 11, 2017, 05:58:25 AM »
I plumbed a couple of dozen new homes with it. I ran 3/4" as trunk lines, then teed off with 1/2" to all fixtures. Never had an issue with pressure or volume. In reality, all modern fixtures are made to limit flow, so there really is no need provide excess volume to the fixture, since it won't be used anyway. If you haven't bought any tools or fittings yet, take a look at the stainless steel band clamps and pliers. Far superior to the compression band style and it needs one inexpensive tool to do all sizes of pipe.

Skills Barterer

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Re: Copper to Pex
« Reply #4 on: August 11, 2017, 06:12:20 AM »
I would also make sure to measure the outer diameters of the copper, and the inner diameters of your planned adapting fittings before splicing to make sure they will fit.  If it is really old copper you may have some fitment issues. 

Roboturner

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Re: Copper to Pex
« Reply #5 on: August 11, 2017, 08:14:24 AM »
I am not sure that 50' is actually considered a short run, but it is more important to be aware of how many connections are coming off of each run. ie Are you making a run to the upstairs bathroom wherein the shower, sink and toilet will all be fed by it?

to be honest their more like 10'

yes one upstairs bathroom split and one downstairs bathroom split
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Roboturner

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Re: Copper to Pex
« Reply #6 on: August 11, 2017, 08:16:46 AM »
I plumbed a couple of dozen new homes with it. I ran 3/4" as trunk lines, then teed off with 1/2" to all fixtures. Never had an issue with pressure or volume. In reality, all modern fixtures are made to limit flow, so there really is no need provide excess volume to the fixture, since it won't be used anyway. If you haven't bought any tools or fittings yet, take a look at the stainless steel band clamps and pliers. Far superior to the compression band style and it needs one inexpensive tool to do all sizes of pipe.

perfect, and yes i read similar suggestions on SS crimps vs copper compression rings, so that was my thought
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BudgetSlasher

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Re: Copper to Pex
« Reply #7 on: August 12, 2017, 08:25:26 AM »
I've used PEX to augment and relocate runs in a copper trunk and branch system (the flexibility of PEX is a real lifesaver when threading up an existing wall). I've always used 1/2 for the run to fixtures and I have never had a complaint on the water pressure.

PEX has a smaller ID than copper, but the explanation I have heard goes like this; due to the flexibility of PEX you can make 90 degree turns using an external guide with a larger radius than a copper 90 degree elbow, which in turn reduces resistance. So, basically minimize the fittings you use and you should be ok.