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-   -   Is 1/2 Pex more restrictive than 1/2 copper? (http://www.diychatroom.com/f7/1-2-pex-more-restrictive-than-1-2-copper-22379/)

twilightcall 06-17-2008 06:05 AM

Is 1/2 Pex more restrictive than 1/2 copper?
 
I have read on this site that Pex is restrictive. Can anyone explain why 1/2 Pex is more restrictive than 1/2 copper? I would think Pex would be less restrictive due to being very smooth. Any info would be appreciated.

clasact 06-17-2008 06:18 AM

what do you mean by restrictive? I have Pex through out my house with no problem what so ever

RippySkippy 06-17-2008 08:01 AM

With out researching it throughly, I'm guessing the reference comes from the fact that the Pex fitting fits inside the pipe, therefor you have a much smaller diameter for water to flow as it passes through fittings.

My house has Pex with a manifold and home run system...and it's not caused any problems whatsoever. The only place I up-sized was for the 90 gal bubble tub, it's run at 3/4" with high flow fixtures. Most residential installations won't see a problem if they there is adequate pressure and flow to the house to begin with, of course that's just my take.

Alan 06-17-2008 09:12 AM

if you're talking about my post about using pex for a tub spout, i'm referring to the inside diameter of the fitting, which is closer to 3/8"

The pipe is the same diameter, but copper fittings go on the outside, and the pex fittings go on the inside.

clasact 06-17-2008 10:16 AM

Ok now this depens on where you live because some places have code against this.I ran a system like RippySkippy,off a manifold I ran 3/4 pex but use shark bite fitting instead of the crimp type.The fitting fit over the outside so no reduction of size but like I said they are not code in all places.If you are allowed to use them they are a bit on the high end of price but for time saveings and ease and reusability they cant be beat.I have had them for over two years now and no leak or problems at all and I have had to reconfigure a couple of lines due to differant renovations.They do make them with shut offs and thread type for attaching supply lines to and reduction type also.I have had no reduction in water presure as a matter of fact I saw an increase once it was all set up.As I stated though if codes apply check to see if you can use them first.Some may not agree with how I ran mine but it works great for me.

twilightcall 06-17-2008 12:44 PM

Thanks guys. I appreciate the info. I was referring to the pex fittings. They get fairly narrow and the copper fittings go on the outside so I just wanted to know if anyone has had problems with the water flow due to the fittings etc.

Termite 06-17-2008 04:01 PM

It'll vary depending on system setup, flow, and pressure. Most 1/2" pex fittings neck down to 3/8" at the fitting. There are systems that expand the pex to fit over an actual 1/2" fitting, but they're less common and the tools are expensive.

I ran regular Zurn/QuestPex 1/2" in my house to every fixture, with the fittings that neck down to 3/8". I replaced a 1/2" copper system. I saw no reduction in flow or pressure at all. The sinks and showers work the same, and the toilet fills just as fast.

Alan 06-17-2008 09:44 PM

Quote:

Originally Posted by thekctermite (Post 131215)
It'll vary depending on system setup, flow, and pressure. Most 1/2" pex fittings neck down to 3/8" at the fitting. There are systems that expand the pex to fit over an actual 1/2" fitting, but they're less common and the tools are expensive.

I ran regular Zurn/QuestPex 1/2" in my house to every fixture, with the fittings that neck down to 3/8". I replaced a 1/2" copper system. I saw no reduction in flow or pressure at all. The sinks and showers work the same, and the toilet fills just as fast.

Even if you try to use all the fixtures in the bathroom at once? :huh:

Termite 06-17-2008 10:21 PM

We've used the sink and the shower at the same time with no noticeable drop. I'm sure there's a difference, but you gotta be more observant than me to notice it.

Alan 06-17-2008 11:39 PM

Well, just for the sake of argument, you'll probably never, or rarely use all of those fixtures at once, but I just repiped my house in pex, and I turned the tub spout on full bore cold, turned the lav wide open cold, and flushed the toilet, and it was definitely noticeable...... still useable? Yes. :yes:

But if you like to put out fires while you take a shower......

RippySkippy 06-18-2008 07:59 AM

For the reasons mentioned regarding pressure/flow drop, that's why I like manifolds and home runs. While it may not eliminate all flow/pressure issues, it certainly can't hurt when you have a 3/4 inlet and 1/2 out, in theory, the impact should be minimal. Not saying it's right, just know it works.

Termite 06-18-2008 08:46 AM

Quote:

Originally Posted by RippySkippy (Post 131412)
For the reasons mentioned regarding pressure/flow drop, that's why I like manifolds and home runs. While it may not eliminate all flow/pressure issues, it certainly can't hurt when you have a 3/4 inlet and 1/2 out, in theory, the impact should be minimal. Not saying it's right, just know it works.

Absolutely. I'm on board with running as many lines as possible off a larger manifold setup. That is definately the best installation. There are so many variables in play...What works well in one house will work differently in another.

bazmanblue 06-20-2008 10:24 AM

pex has known to have failures when in direct contact with sunlight and extreme temperatures of hot water running through it.

RippySkippy 06-20-2008 11:22 AM

Quote:

Originally Posted by bazmanblue (Post 132085)
pex has known to have failures when in direct contact with sunlight and extreme temperatures of hot water running through it.

You are right, but there's more to what you're implying.

Wirsbo, now Uponor, plumbing specs say to avoid sunlight exposure to 30 days and the temperature/pressure chart is:
200F (93C) at 80 psi (551 kPa)
180F (82C) at 100 psi (689 kPa)
73.4F (23C) at 160 psi (1,102 kPa)
So yes there are limitations, and as DIY'ers we all should be aware of a specific product limitations and know what we are dealing with. In our living situation all pipes are protected from sunlight, so that's not an issue, and our pressures are well below those stated.

mstplumber 06-20-2008 11:45 PM

For what it's worth:

Although most PEX manufacturers really push manifold systems, could that be because a manifold system uses a lot more pipe?

While a manifold system may be an acceptable choice in some applications, there are several factors which need to be considered. Manifold systems often waste water. This is because of the need to clear the cooled water out of hot water lines when you want hot water. When the hot water has not been used for a while the water in the pipes cools down (unless you have a circulating system of some kind). In order to get hot water, most people just let the cooled water run down the drain until it heats up. With a standard, "non manifold" system this usually only has to be done once at each bathroom group. With a manifold system each fixture has to have it's supply purged of cooled water separately. Even though the individual lines are usually 1/2" instead of 3/4", if you do the math you will see that that is more water wasted, especially if 2 people are using separate faucets in addition to the shower.

Another drawback of a manifold system is that you can't effectively install a circulation system if one is needed. This shortcoming again can contribute to wasted water going down the drain. Since water conservation is an increasing concern, this needs to be considered when choosing a water distribution design.

Cost is another factor. Manifold systems simply cost more due to the increased material requirements.

I know I'm going across the grain here and that there are thousands of houses out there with manifold systems. They certainly minimize the possible leak points in a piping system. They are not, however, for every application. They are also just not very "green". They use more material and contribute to less overall water and energy efficiency in the home.


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