Copper or PEX

I just received a price to upgrade the hot and cold supplies for my new shower.
We want to upgrade from 1/2" to 3/4".

The plumber says I can save about $600 by using PEX instead of copper.
He tells me there is no difference between using copper or using PEX.

Will 3/4" PEX give me the same amount of water flow as 3/4" copper will?
I concerned that upgrading from 1/2" copper to 3/4" PEX give me little or no benefit.

Just use the type of PEX that doesn't have a lawsuit that's leaking/bursting behind the walls. There's quite a few of them now and some have quit being manufactured.

First of all let me say that I am not a pro. Secondly, let me say that this is my opinion without a lot of scientific facts to back me up. Therefore, take it as personal opinion. I would never use PEX if copper was possible. PEX is not yet proven to be reliable in the the long term. There have been problems with the material and with the fittings. I know there have been improvements, but the track record isn't there yet. Copper is a proven product without the potential problems of PEX. That's my opinion and I'm sticking to it.

Dunbar Plumbing said:

Just use the type of PEX that doesn't have a lawsuit that's leaking/bursting behind the walls. There's quite a few of them now and some have quit being manufactured.

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I'm not asking about the quality. I'm asking about it's ability to carry the same amount of water. Will 3/4" PEX carry the same amount of water to my shower as 3/4" copper will?

3/4" pex will supply you with just as much water as 3/4" copper and is way more affordable not only on material cost but the labour takes way less time

Dom Z said:

I'm not asking about the quality. I'm asking about it's ability to carry the same amount of water. Will 3/4" PEX carry the same amount of water to my shower as 3/4" copper will?

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Well, since you don't care about quality...


3/4" PEX has a thicker wall than 3/4" copper.

Depending on the type of PEX used will determine the flow rates on copper against PEX. There will be a difference.


I've never seen a gain in upsizing the lines to a shower, it's all ported down to 3/8" on those valves "most the time" and the gains aren't achieved. But I do and charge the customer for what they ask of me.

copper was my choice

I agree with Gary. He has pretty much relayed my thoughts on PEX.
I am not a scientist, nor a plumber, either.

Recently finished a replumbing of the house we bought last summer. The entire house was replumbed from the meter on with type L copper. We also added a full bath upstairs - so now we have 2½ baths instead of 1½. The plumber we had did a really nice job. All that new shiny copper, soldered joints, ball valves, etc. is a sight to behold. Looking at it now I am extremely glad did not go with PEX - espcially given the problems that seem to be now appearing with NIBCO's Dura-Pex. Ironically, last summer we actually purchased two rolls of the Dura-Pex but, then decided to go with copper. Looks like maybe the only PEX that may be of decent quality may be the Wirsbo/Uponor Aquapex products.

Copper prices have fallen dramatically since last summer. Around here 10' 3/4" Type L was $19, now around $13.

No material is perfect, but I will stick with copper for the time being until all the issues with PEX are worked out.

Matt

No, 3/4" PEX will not carry as much water as 3/4" copper at equal pressure. PEX has thicker walls, therefore the inside diameter is smaller. The same is true for CPVC also.

A 1/2" supply pretty much taps out at around 6gpm, and as you get to the upper end, you'll probably notice a decrease in pressure. Ideally, you can supply more water than the valve can flow. This will keep the pressure up (think finger over the end of a hose). 3/4" copper can flow around twice that of 1/2". 3/4" pex is somewhere in-between, and in your situation, should probably work fine.

Wirsbo uses a fitting that is larger than those that use a crimp, so it can flow more with the same pipe than the other systems. When I had my bath redone, they used WIrsbo pex...so far (5-years) so good.

Like stated above, 3/4" Pex=1/2" copper in terms of Inside Diameter(ID).

1" Wirsbo fittings and Wirsbo Aquapex will do the trick just fine.

I disagree with alot of what has been said here.

I looked at my pipe flow tables developed from the university down the road from me.

Coldwater flowtable.

Copper should only be at 5'/second max.
at 1/2 Copper has 3.64 GPM
at 3/4 copper has 7.54 GPM

Pex-al-pex can be used at 8ft/second
at 1/2 Pex-al-Pex has 5.8 GPM
at 3/4 Pex-al-Pex has 12 GPM

The university also has a small piece of pex under pressure @ 500 psi for the last 8 years, it sure has ballooned out and expanded but it has yet to rupture.

Personally all I install is Pex-al-Pex, and am completely confident in the product, I like wirsbo even better and it has better flow rates, but is slower to install and a bit more expensive in my area. About 8 years ago, I did a multi million dollar house all in pex, it was in a ski resort and was in the wintertime. I pressure tested it at 200 psi hydrostatic, and for reasons beyond my control I left the test on for several days. It got really cold and the lines completely froze, when i was able to return, I expected to have to replace the whole system. I brought alot of propane heaters, set them up, plastic'd off the windows and warmed the house. I thawed the whole system and retested it back at 200psi, unbelievably there was no leaks and no damage to any fittings. I kept the house heated and under test for several days at 200psi to make sure, 8 years later and I have never had a callback.
I am completely sold on the product and have used it extensively since, Every other contractor uses it in this area as well. The only place we use copper is on valves, down to the tub spout and up to the showerhead just to make it rigid.

Edit:

Personally I always bring 3/4 pex to shower valves and tub valves, but thats just because I like to be prepared incase the home owner changes their mind about valves and potential setups. I agree with dunbar Plumbing if you dont have the right valve, you wont see an improvement, make sure you get a 3/4 valve for the set up your talking about...

Like Ted said, size your lines accordingly, I only ever run 3/4 to two bathrooms at the max (17 fixture unit is code in my area, 2 standard bathrooms would be 12 FU), then 1" from there, but I have been known to be a bit overkill, and have built a reputation on it.

The critical thing on copper is you don't want the flow greater than about 6'/second, and that does calculate to around 3.6gpm (if I did my math right). But, you'll be mixing a fair amount of cold into the hot, so what you'll get out of the mixing valve should exceed that by a fair amount, but not double. Depends on the relative temps and your desired setting. Pex may have a smoother interior and fewer corners to go around, but if there's any copper in the path, you still don't want to exceed the flow rate to prevent excessive wear on the copper piping (unless you increase the diameter). All by itself, because it is smoother, it can probably support a higher flow rate without wear, but it would require fairly high pressure to get that flow.

If you want to do the calcs yourself, a gallon = 231 cu in at room temp.

jadnashua said:

The critical thing on copper is you don't want the flow greater than about 6'/second, and that does calculate to around 3.6gpm (if I did my math right). But, you'll be mixing a fair amount of cold into the hot, so what you'll get out of the mixing valve should exceed that by a fair amount, but not double. Depends on the relative temps and your desired setting. Pex may have a smoother interior and fewer corners to go around, but if there's any copper in the path, you still don't want to exceed the flow rate to prevent excessive wear on the copper piping (unless you increase the diameter). All by itself, because it is smoother, it can probably support a higher flow rate without wear, but it would require fairly high pressure to get that flow.

If you want to do the calcs yourself, a gallon = 231 cu in at room temp.

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5'/second (3.6GPM) any more then that and its too much wear on the copper pipe, the pex pipe can handle higher rates, up to 8'/second which is what the pex table is based on, thanks for pointing that out as it was missleading and that was not my intention I changed the table above so it does not look misleading as it did before.