Preferable method for PEX connections?

EricPeterson

I am planning on doing a run of 3/4" PEX through an interior wall to hook up a radiator on the third floor of our house. The PEX will transition to black iron at the boiler and to copper on the third floor. I will need to add terminations for the PEX fitting.
PEX is new to me so I was wondering about the crimp vs clamp fasteners.
Any reason to choose one over the other for this small project?

Thanks,
Eric

mattmia2

I like ProPex but you need to use PEX A for it. You can get a knockoff expansion tool relatively inexpensively. It is especially good because you can expand it out in the open and shove it over a fitting in some dark corner before it shrinks, you don't need to get a tool near the actual connection.

hot_rod

It comes down to which tools you want to invest in. The expansion pex fitting ASTM 1960 allows a bit more flow, but you need an expander tool to work it. Both insert and expansion fittings shown below.

Some of the pex B companies allow expansion now. Not my favorite combination. Rehau, Uponor, Mr pex are good A brand cold expansion tube.

I've used mostly the copper or stainless crimp type fitting. Works with any pex tubes. The stainless Viega rings work and look nice.

I don't care for the pinch ring type connection.

ChrisJ

I also vote for Propex expansion connections.
They also let you expand the tubing and then slip it over the fitting, so the tool doesn't need to fit into a tight space where the fitting may be.

I bought a barely used Uponor manual expander from Ebay many years ago. 3/4" will give you a workout but it'll get the job done.

Larry Weingarten

Hi, I use Uponor. Expansion fittings just have better flow. In your job, the only concern is that you’ll probably use a brass fitting to get from iron pipe to PEX, and I’ll wonder out loud about galvanic corrosion. Thoughts anyone?

Yours, Larry

mattmia2

Brass to black iron/steel is fine especially in a closed system.

hot_rod

Brass and steel are very close on the galvanic chart, very low potential for electrolysis 

Larry Weingarten said:

Hi, I use Uponor. Expansion fittings just have better flow. In your job, the only concern is that you’ll probably use a brass fitting to get from iron pipe to PEX, and I’ll wonder out loud about galvanic corrosion. Thoughts anyone? Yours, Larry

HomerJSmith

I have used Oetiker pinch clamps with great success on Pex A. Using Uponor Pex expandable sleeves saves the use of multiple tools. You just need an expandable tool which is cheap on the internet. Just use Uponor fittings.

Condoman

10 years ago I moved to my current home and had to work with my first PEX. I used the SS cinch rings because the tool was the best price for me and I could get the fittings at the big box stores. Now it is harder for me to operate the tool so I treated myself to the Roybi tool that gets in tight places and is easy for me to operate.

mattmia2

I think the pex expansion fittings are less likely to differentially expand and contract over time and cold creep from the plastic expanding more than a metal ring and loosen up over long periods of time.

4Johnpipe

First make sure to use HePex with oxygen barrier for heating…Cold expansion is easy and really my preferred method…you can get threaded, sweat or now even press adaptors.
If you ask most supply houses have a tool rental policy and just buy an extra expansion collar or two and practice making up a fitting…cut the collar and go to work.

Camdo

What about leakers. Has anyone seen a leaky PEX connector? If so, what kind was it. New or old. What's the longevity confidence factor compared to copper sweat? Will these PEX joints last 100 years? How confident are you with PEX joints in concealed ceiling spaces of 'your' home. What's the comfort factor in using this stuff? I definitely do not want to ever cut drywall in my home to fix a leaking joint. My motto, "Install once and forget til I die".

MaxMercy

Camdo said:

I definitely do not want to ever cut drywall in my home to fix a leaking joint. My motto, "Install once and forget til I die".

I have to re-pipe my house soon. Pinholes in the copper. I hate walking into the kitchen first thing in the morning and finding a puddle from the ceiling.

There is no fool-proof pipe system. With perfect water, copper would be my preference, and that would be sweated copper, not press (I don't trust O-rings long term). With PEX, an expansion system makes the most sense. In a crimp type installation, the PEX is pushing back against the crimp forever trying to loosen it. In an expansion system, the PEX is forever trying to clamp down harder on the fitting. I would think the expansion connection will outlive the pipe.

ChrisJ

Camdo said:

What about leakers. Has anyone seen a leaky PEX connector? If so, what kind was it. New or old. What's the longevity confidence factor compared to copper sweat? Will these PEX joints last 100 years? How confident are you with PEX joints in concealed ceiling spaces of 'your' home. What's the comfort factor in using this stuff? I definitely do not want to ever cut drywall in my home to fix a leaking joint. My motto, "Install once and forget til I die".

I believe leaks with ProPex expansion connections are extremely rare, and can even stop on their own.

With any kind of crimp style, if it leaks it will keep leaking until you redo the connection.

Camdo

Whenever I think of PEX, I think of the plastic trash cans that we sold guaranteed for 40 years! Well that never happened. The plastic would become embrittled over time and crack. I am skeptical. There has been bad copper in the past and I know there will be bad PEX. Which material is more robust to manufacture? Knowing plastic manufactures work on the slimist margins does not build confidence.

ChrisJ

Camdo said:

Whenever I think of PEX, I think of the plastic trash cans that we sold guaranteed for 40 years! Well that never happened. The plastic would become embrittled over time and crack. I am skeptical. There has been bad copper in the past and I know there will be bad PEX. Which material is more robust to manufacture? Knowing plastic manufactures work on the slimist margins does not build confidence.

Trash cans are left out in the sun.
Sunlight kills many if not most plastics especially polyethylene.

Polyethylene pipes (the thick black plastic pipes that come in rolls) have been around since at least the 1950s and they hold up extremely well, perhaps better than any other. The house I grew up in had several polyethene pipes that were exposed to sunlight outdoors for no less than 40 years and they were still acceptable.

PEX is crosslinked polyethylene.

The #1 rule with pex is do not expose it to sunlight.
I'm sorry but, you cannot compare plastic garbage cans left outside to pex plumbing.

knownspace

My experience is that expansion fittings are the preferred choice for any behind the wall installation.
I Personally would never use crimp fittings as a permanent connection. There have been some posts that say crimp connections are better able to handle temp expansion differentials but in fact expansion joints at superior as the expansion coupling is the same material as the pipe and will expand and contract at the same rate. PEX also has ‘memory’ to return to it original size, increasing the strength of the connection for the life of the product. I have installed thousands of pex joints and have never had a failure. Also use Uponor products, they are the best.

ChrisJ

knownspace said:

My experience is that expansion fittings are the preferred choice for any behind the wall installation.
I Personally would never use crimp fittings as a permanent connection. There have been some posts that say crimp connections are better able to handle temp expansion differentials but in fact expansion joints at superior as the expansion coupling is the same material as the pipe and will expand and contract at the same rate. PEX also has ‘memory’ to return to it original size, increasing the strength of the connection for the life of the product. I have installed thousands of pex joints and have never had a failure. Also use Uponor products, they are the best.

I'm fairly certainly that pex having memory is primarily pex A.
B and C may have it to an extent, but not as much as A.

At least, that's what I'm remembering.
This is why pex A in a roll straightens out on it's own pretty well but pex B from a roll will tend to stay bent pretty much forever unless you force it straight.

mattmia2

ChrisJ said:

At least, that's what I'm remembering.
This is why pex A in a roll straightens out on it's own pretty well but pex B from a roll will tend to stay bent pretty much forever unless you force it straight.

I did not have good experiences with 1" pex a in a roll. i may have just been too impatient. i ended up stretching it out between posts in my yard in the sun and letting the heat help it straighten out enough that i could get it to go where i wanted it to.

hot_rod

ChrisJ said:

knownspace said:

My experience is that expansion fittings are the preferred choice for any behind the wall installation.
I Personally would never use crimp fittings as a permanent connection. There have been some posts that say crimp connections are better able to handle temp expansion differentials but in fact expansion joints at superior as the expansion coupling is the same material as the pipe and will expand and contract at the same rate. PEX also has ‘memory’ to return to it original size, increasing the strength of the connection for the life of the product. I have installed thousands of pex joints and have never had a failure. Also use Uponor products, they are the best.

I'm fairly certainly that pex having memory is primarily pex A.
B and C may have it to an extent, but not as much as A.

At least, that's what I'm remembering.
This is why pex A in a roll straightens out on it's own pretty well but pex B from a roll will tend to stay bent pretty much forever unless you force it straight.

B pex is cross linked after it is coiled, that is why it likes to stay coiled.
A is cross linked as it is extruded, then coiled. A tends to be easier to work, especially in cold.

The other concern with pex is highly chlorinated or other chemicals and running continuous circulation at elevated temperatures, 120- 140. That is a condition causing pex failures in DHW systems.
The CL listing on pex tube is one of the toughest test it undergoes. Only one brand claims to meet the highest test standard. Homeowners with failed tube tend to disagree

Chlorine an chloramine are the most common treatments now. 5- 10 years from now???

Homerun pex would be my choice in a new home if connections in the wall scare you. No need for recirc either.

rick in Alaska

I use pex A with expansion fittings. I use the expansion fittings just because I don't like any restriction, no matter how small. The difference between pexA, and B, is that you can bend A all day, and it just kinks, where as you can bend B a few times and break it in half, which is not good when you are dealing with any bends.
I personally do not have any problems with crimp rings, and in some cases have to use them. I'm not sure I agree with the others about pipe expanding back and forth with them and coming apart, as I do not believe the ring is going to allow it, so I would not be concerned about putting it in a wall.
I have used the cinch rings just a little when I couldn't get the crimp rings and found them to be ok. However the only pex leaks I have ever had was on one, and I have heard some people concerned about the ring snapping, so when I have had to use them, I put two on 180 degrees apart. So far so good. ( actually I have had a few expansion leaks when I put pipe together when it was cold, but now I just use my heat gun to warm them up a bit before I turn the water in.)
Also, I have found Rehau fittings work just as well as Uponor in expansion tubing.
Rick

ChrisJ

hot_rod said:

ChrisJ said:

knownspace said:

My experience is that expansion fittings are the preferred choice for any behind the wall installation.
I Personally would never use crimp fittings as a permanent connection. There have been some posts that say crimp connections are better able to handle temp expansion differentials but in fact expansion joints at superior as the expansion coupling is the same material as the pipe and will expand and contract at the same rate. PEX also has ‘memory’ to return to it original size, increasing the strength of the connection for the life of the product. I have installed thousands of pex joints and have never had a failure. Also use Uponor products, they are the best.

I'm fairly certainly that pex having memory is primarily pex A.
B and C may have it to an extent, but not as much as A.

At least, that's what I'm remembering.
This is why pex A in a roll straightens out on it's own pretty well but pex B from a roll will tend to stay bent pretty much forever unless you force it straight.

B pex is cross linked after it is coiled, that is why it likes to stay coiled.
A is cross linked as it is extruded, then coiled. A tends to be easier to work, especially in cold.

The other concern with pex is highly chlorinated or other chemicals and running continuous circulation at elevated temperatures, 120- 140. That is a condition causing pex failures in DHW systems.
The CL listing on pex tube is one of the toughest test it undergoes. Only one brand claims to meet the highest test standard. Homeowners with failed tube tend to disagree

Chlorine an chloramine are the most common treatments now. 5- 10 years from now???

Homerun pex would be my choice in a new home if connections in the wall scare you. No need for recirc either.

I run Uponor with recirculating hot water in both my house and my parents house.
I have city water, they have well water.

No, you don't need recirc, but as I said in the other thread, we don't need central heating or electric or indoor plumbing either.

Once you get used to having hot water immediately, especially late at night, if you or the kids are sick etc, you never want to go back. I get hot water to both bathroom sinks in about 2 seconds as I planned the shortest amount of piping outside the loop to both sinks I could. I think there's about 12" of 1/2" pex and supply tube to one sink, and if you count the supply tubing in the cabinet probably 2' to the other sink.

If that causes my Uponor tubing to fail in 10 years, all well. It is what it is.
Uponor claims their tubing is good for chlorinated city water at 140F with constant circulation. I know, companies claim a lot of things, but I have to hope they're right.

hot_rod

So the test for longevity is an extrapolated test. In believe a 2 week test at extreme temperature and velocity. 50 years is what comes out of that extrapolation. I like that word, gonna use it more often

The very first of many numbers on Pex tells the most about the chlorine listing. So not all pex is created equally. Look for the brands that have the highest certifications. Certainly not one that starts with 0!

ChrisJ

hot_rod said:

So the test for longevity is an extrapolated test. In believe a 2 week test at extreme temperature and velocity. 50 years is what comes out of that extrapolation. I like that word, gonna use it more often

The very first of many numbers on Pex tells the most about the chlorine listing. So not all pex is created equally. Look for the brands that have the highest certifications. Certainly not one that starts with 0!

All PEX manufacturers are required to test their pipe’s resistance to hot, chlorinated water and list the PEX designation on the pipe’s print stream. Uponor PEX-a pipe meets the highest requirement for chlorine resistance at end-use conditions 100 percent of the time at 140°F (60°C).

EricPeterson

This has been a lively discussion.

Since my initial post I've had to work on figuring out an old K&T wiring issue, now solved, part of the reno work being done on the third floor of our house.

So to recap my situation, my boiler is in the basement, and I want to add a radiator on the third floor.

I have a clear shot up an interior wall for pulling some 3/4" PEX. In the basement I need to make two 90° bends to direct the PEX towards the boiler location, before transitioning to black iron. I hope to utilize 3/4 bend support brackets for these bends. Like these from SupplyHouse. I think I can manage a 7.5" bend radius in the space where I am making the bends.

On the third floor I need to make three 90° turns to get the water over to the radiator elbows. Due to the tight space this is where I hope to use PEX 90° fittings for some of the turns. Or I could transition to copper to connect to the radiator elbows.

I found some 3/4 oxygen barrier PEX at Menards (Sioux Chief), but I also see product available at SupplyHouse. I don't mind paying for the better product.

As for fittings I see that many have recommended the expansion joints. For such a small project I am unsure as to whether or not these would be the best choice. I guess either way (crimp / cinch or expansion) I am going to need a special tool for this job.

Now it will be a race against time to see if I can get all the other work done on the third floor before the carpet installation, and have time to install this radiator. It would provide heat to a currently unheated loft area at the top of the stairs. All about the comfort.

PEX would come up on the right, make a 90° bend behind the conduit, then a 90° bend through the sidewall, then a final 90° bend to point to the wall where the radiator will be placed. I will make a small enclosure to hide the piping on the radiator sidewall.
If necessary I could pull the electrical box forward a little from the wall temporarily to get a little more working space.

Eric

Larry Weingarten

Hi, Ebay is a good place to hunt.
https://www.ebay.com/itm/142697277045?epid=18031753517&hash=item21396ba675:g:Zi8AAOSwFEpajSiE&LH_BIN=1

Yours, Larry

rick in Alaska

You might also think about running 5/8 pex for that run, or if it a small enough baseboard, you can even do it in 1/2". Either one of these would be easier than running 3/4". Wirsbo makes a 5/8 to 3/4 baseboard 90, but if you used 1/2", you would have to put a couple adapters together.
Rick

hot_rod

If you are talking just a few fittings in the loop, the insert fittings with a copper or stainless ring will be fine. I prefer copper or brass fittings for work like that.
Looking at all the fittings and their track record, the insert with crimp rings have the best track record when properly applied.
Seems to be some bad expansion pex connection failures out there. After all these years of expanding?!

I guess it comes down to what tool you can come up.

3/4" coil pex can be a bear to work with in tight quarters. 1/2 if it can handle the load will be light years easier to handle. 10- 12,000 BTU through 1/2" easily.

Camdo

I'm wondering what types of fittings survive a hard freeze better. The metal ring type may expand a bit during a hard freeze and loose some clamping / sealing effectiveness. The expand push on type may have less resistance to push off during a hard freeze. What are the experiences with hard freeze survivability?

hot_rod

Camdo said:

I'm wondering what types of fittings survive a hard freeze better. The metal ring type may expand a bit during a hard freeze and loose some clamping / sealing effectiveness. The expand push on type may have less resistance to push off during a hard freeze. What are the experiences with hard freeze survivability?

I doubt one is better than the other in freeze ups. The tube usually expands enough to take a freeze without pushing a fitting off. Keep in mind copper tube will also push a soldered fitting off.
Best to keep it from freezing.

Larry Weingarten

Hi, Freezing of PEX was studied at NREL by Jay Burch, and water freezes first at metal fittings, expanding towards the tubing. It winds up rupturing the tubing away from metal fittings. A lot depends on the distance between fittings. Worst case is fittings not too far apart... they freeze and expand towards the center of the tubing, creating tremendous hydraulic force. Might be good to look here: https://heatinghelp.com/systems-help-center/how-many-times-can-pex-freeze-before-bursting/#:~:text=A study at NREL was done on freezing,were freeze-thaw cycled over 500 times without damage.

Yours, Larry

fixitguy

I've been using SharkBite for years. Doesn't seem like anyone else uses them, I have never had a failure though. Otherwise soldered L pipe

LMacNevin

A great place for information on PEX tubing and systems is PPI, a non-profit trade association. We publish non-biased technical information related to all types of PEX and PEX fittings, and it's all online for free.

This is the PEX webpage: https://plasticpipe.org/BuildingConstruction/BuildingConstruction/PEX.aspx

Presentation about PEX tubing and fittings (lots of pictures): https://plasticpipe.org/common/Uploaded files/1-PPI/Divisions/Building and Construction/Division Publications/Presentations/Designing PEX Plumbing Systems to Optimize Performance and Efficiency/BCD-presentation-designing-pex-plumbing.pdf

Presentation about UV resistance: https://plasticpipe.org/common/Uploaded files/1-PPI/Divisions/Building and Construction/Division Publications/Presentations/BCD-presentation-uv-resistance-pex.pdf

PPI TR-52 report about Freeze-break resistance: https://plasticpipe.org/common/Uploaded files/Technical/TR-52.pdf

I've been in the plastic pipe industry since 1993 and am happy to address any technical questions on PEX or other plastic pressure pipes. Feel free to contact me directly.

LMacNevin

By the way, all PEX tubing must be tested to ASTM F876, which includes the Stabilizer Functionality test to ensure it will meet long-term exposure to hot water. The test was based on research performed in Europe decades ago to ensure that hydronic PEX is up to the job.

It says, "The functionality of a stabilizer in a specific PEX compound shall be verified by hydrostatic testing of pipe made from the compound. Test six pipe samples continuously for 3000 h at a hoop stress of 0.70 MPa at 120 °C, or for 8000 h at a hoop stress of 2.8 MPa at 110 °C. This test is used to demonstrate the specific compound’s ability to withstand long term temperature conditions set forth elsewhere in this standard."

The first requirement is 125 days of continuous water pressure of 25 psig at 248F. The second requirement is 333 days of continuous water pressure of 100 psig at 230F. No failures are allowed.

The capabilities of PEX are higher than most people know.