# Is 1/2 Pex more restrictive than 1/2 copper?



## clasact (Oct 21, 2006)

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


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## RippySkippy (Feb 9, 2007)

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.


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## Alan (Apr 12, 2006)

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.


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## clasact (Oct 21, 2006)

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.


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## twilightcall (Jan 4, 2008)

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.


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## Termite (Apr 13, 2008)

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.


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## Alan (Apr 12, 2006)

thekctermite said:


> 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:


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## Termite (Apr 13, 2008)

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.


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## Alan (Apr 12, 2006)

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......


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## RippySkippy (Feb 9, 2007)

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.


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## Termite (Apr 13, 2008)

RippySkippy said:


> 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.


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## bazmanblue (Jun 20, 2008)

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


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## RippySkippy (Feb 9, 2007)

bazmanblue said:


> 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:200°F (93°C) at 80 psi (551 kPa)
180°F (82°C) at 100 psi (689 kPa)
73.4°F (23°C) 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.


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## mstplumber (May 3, 2008)

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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## RippySkippy (Feb 9, 2007)

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


Don't know...to me it seems like the pipe is quite reasonable compared the cost of the fittings.



> .....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.


You bring up some valid points here...won't argue that. I think the balance is somewhere in-between a home run and "traditional" system. For example, when I ran my pipe for the master bath...by far the longest run ~100'. For the reasons you mention, I ran one hot and one cold to the group and split to each fixture, more like a traditional system. I could not see the value in running two hots and two colds for a vanity sink. Likewise, the shower and bubble tub share a H & C, I'm betting they will not be used at the same time. The stool got it's own run just because.



> Another drawback of a manifold system is that you can't effectively install a circulation system if one is needed.


Please share more here...mine works well, maybe it doesn't know it's not supposed to :whistling2:




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


Not for us DIY'ers, buy when it's on sale and stock pile. Again, I thought the pipe was cheep compared to the fittings, and with the price of copper, I think the PEX is still ahead.



> 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.


Wow...that's just tossing a load out there. I would be interested in reading up on the publications that support your view...I thought I was making the right choice based on my reading as well.

I agree and there's not a one-size fits all for any installation. In my old house, it took 3 minutes for the hot water to reach the kitchen, in the old traditional pipe method. The "bonus" was that when you turned the water off, the copper effectively cooled the pipe contents. Pause for a few minutes and you get to re-purge the lines, that's not green. Energy efficiency in home certainly does not begin with the distribution of commodity, it starts with it's creation, i.e. hot water begins at the heater, warm air begins at the furnace or boiler. I installed a 93% efficient boiler, with a 40 gallon indirect domestic hot water heater. The same boiler provides the heat for the radiant in-floor, as well as the heat for the forced air. This is installed in an ICF house. When I have a chance to do it again, I would do it the same way.

The PEX system is a great advancement in residential water distribution. I haven't heard of one house being ransacked for it's PEX contents! If your house is one of the unfortunate to be claimed by the urban miners, you get to double the price of install...that's not green. The manifold I installed has a ball valve on each line in the run, IF there's a leak, or a need for maintenance, it's really easy to turn off only what's needed with out affecting the rest of the home.

I've worked quite a bit with copper, and like to sweat the joints. When it's done, it looks great. I too was skeptical about PEX at first, but when I installed it in our home, a buddy and I ran the whole house in one day...so the labor savings has to account for something, which wasn't addressed. When I pressure checked at the end of the day, there wasn't a single leak. I was amazed. Until I see or hear of something better, I'm sold at this point...50 years from now I don't know...but then again I won't be around to see it...most likely.


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## mstplumber (May 3, 2008)

I guess I wasn't clear. I like PEX, a lot. I am just not a big fan of manifold systems. I apologize in advance for the long post but I will try to elaborate. 



RippySkippy said:


> Don't know...to me it seems like the pipe is quite reasonable compared the cost of the fittings.


I have spoken with both Uponor (formerly Wirsbo), Nibco and other PEX manufacturers. They all admit that a manifold system usually has a higher material cost than a properly installed standard "branch" type system. Even though there are less total fittings, the manifold fittings or assembly and the extra pipe usually add up to a higher total cost.




RippySkippy said:


> You bring up some valid points here...won't argue that. I think the balance is somewhere in-between a home run and "traditional" system. For example, when I ran my pipe for the master bath...by far the longest run ~100'. For the reasons you mention, I ran one hot and one cold to the group and split to each fixture, more like a traditional system. I could not see the value in running two hots and two colds for a vanity sink. Likewise, the shower and bubble tub share a H & C, I'm betting they will not be used at the same time. The stool got it's own run just because.


You are right, the cold water side really doesn't affect the efficiency of the system. Again, as you point out, one of the main downsides to a manifold system from an efficiency standpoint is that each hot water line has to be purged of cooled water separately. This wastes water and energy because the volume of cold water being introduced to the water heater from all of the separate hot lines is greater than it would be from one 3/4" hot line. This is because of the heated water that remains in each line after you have turned the fixture off. This means that, in most cases, you are heating a little extra water every time you use hot water at more than one fixture in a bathroom. The further from the water heater the fixtures are, the more inefficient.



RippySkippy said:


> Please share more here...mine works well, maybe it doesn't know it's not supposed to :whistling2:


You got me here, Rippy. I just don't know of a way to install a whole house circulation system with a manifold system. The best I can figure out is to locate the manifold as close to the center of all of the fixtures in order to minimize the distance to each fixture. By definition, a circulation system circulates water through the hot lines to within a short distance of each fixture so there won't be a lot of cooled water that needs to be purged from the lines to get hot water. There are some good aftermarket solutions that don't require a dedicated return loop but they all basically use the cold line as a return and push the cooled water back into the cold side until hot water gets to the fixture. This would only take care of a single fixture on a manifold system.




RippySkippy said:


> Not for us DIY'ers, buy when it's on sale and stock pile. Again, I thought the pipe was cheep compared to the fittings, and with the price of copper, I think the PEX is still ahead.


You are right, PEX is way ahead of copper for value. If you can find PEX pipe on sale and know you have a project coming up you might be able to install a manifold system for less money than a "regular" PEX system. That would really depend a lot on the layout of the project and the price of each individual component. Again, I like PEX and I install it daily, I just prefer a "branch" type system.



RippySkippy said:


> Wow...that's just tossing a load out there. I would be interested in reading up on the publications that support your view...I thought I was making the right choice based on my reading as well.


I'm not saying you made a "bad" choice, or that a manifold system is a "bad" choice. Just that most manifold systems are not as "green" as a properly designed "branch" type system. The concept of "green" as it relates to plumbing is really in it's beginning stages in the USA. There are a lot of factors to consider when determining how "green" a product or practice is. The amount of water that is "wasted" is certainly a factor. It also takes energy to treat both the water before it is used and the waste water after it has gone down the drain. Every ounce of wasted water has a corresponding cost of the energy used to treat and deliver the water and waste. The same is true for the energy used to heat the water. And, provided it doesn't get stolen, less material usually means "greener". I realize that some of these factors may not be directly noticed at a consumer level but they are valid considerations when comparing the overall efficiency of different system designs. 



RippySkippy said:


> I agree and there's not a one-size fits all for any installation. In my old house, it took 3 minutes for the hot water to reach the kitchen, in the old traditional pipe method. The "bonus" was that when you turned the water off, the copper effectively cooled the pipe contents. Pause for a few minutes and you get to re-purge the lines, that's not green. Energy efficiency in home certainly does not begin with the distribution of commodity, it starts with it's creation, i.e. hot water begins at the heater, warm air begins at the furnace or boiler. I installed a 93% efficient boiler, with a 40 gallon indirect domestic hot water heater. The same boiler provides the heat for the radiant in-floor, as well as the heat for the forced air. This is installed in an ICF house. When I have a chance to do it again, I would do it the same way.


I completely agree with all of the above. You have mentioned the number one complaint concerning hot water and one of situations a manifold system sometimes improves. The amount of time it takes to purge the cooled water from a hot line. I agree that this can often be improved by the smaller diameter lines used in a manifold system. This, however, is only true when you are talking about one fixture. The extra time to clear each additional line will usually add up to a longer total time. I think the most efficient water distribution system is one that uses a demand type circulation pump that only operates when hot water is needed and only until it is hot at the point of use. This addresses the number one consumer complaint about their hot water system while allowing the maximum efficiency in doing so.



RippySkippy said:


> The PEX system is a great advancement in residential water distribution. I haven't heard of one house being ransacked for it's PEX contents! If your house is one of the unfortunate to be claimed by the urban miners, you get to double the price of install...that's not green. The manifold I installed has a ball valve on each line in the run, IF there's a leak, or a need for maintenance, it's really easy to turn off only what's needed with out affecting the rest of the home.
> 
> I've worked quite a bit with copper, and like to sweat the joints. When it's done, it looks great. I too was skeptical about PEX at first, but when I installed it in our home, a buddy and I ran the whole house in one day...so the labor savings has to account for something, which wasn't addressed. When I pressure checked at the end of the day, there wasn't a single leak. I was amazed. Until I see or hear of something better, I'm sold at this point...50 years from now I don't know...but then again I won't be around to see it...most likely.


I agree that PEX is a great advancement in residential water distribution systems. I just think that, in most cases, a manifold system isn't the best one. It sounds like you are completely happy with yours so I think you made the right decision in your case. Once again, if I gave the impression that I was not a fan of PEX that wasn't my intent. I think PEX has many advantages over every other option out there today. I am just convinced that the most efficient, "greenest" design cannot be achieved using a manifold system. Though there are admittedly some benefits availible from a manifold system I think the drawbacks outweigh them in the final analysis.

I hope this makes my reasoning a little clearer.


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## RippySkippy (Feb 9, 2007)

> I hope this makes my reasoning a little clearer.


It does, and that my friend is what I LOVE about this site! Great responses.


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## Alan (Apr 12, 2006)

mstplumber said:


> You got me here, Rippy. I just don't know of a way to install a whole house circulation system with a manifold system.


I'd like to know how to do this as well...


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## RippySkippy (Feb 9, 2007)

Whole house? I didn't say you could...look closer at reply #16 there's no mention of a whole house system. The whole house system wasn't mentioned until reply #17.


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