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Thread: General PEX Questions

  1. #1
    DIY Member BillyJoeJimBob's Avatar
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    Default General PEX Questions

    We have a cabin in the mountains in Ruidoso, New Mexico that was homeowner-built (and poorly) in the mid-1070's. Set "pier & beam" style on a mountain, the underside of the cabin is enclosed by uninsulated walls (we call it the "basement"), but it and the plumbing pipes, etc... are exposed and can be worked on easily.

    Due to the age of the PVC pipes, and the possibility we might be renting it to mid-winter skiers, I'd like to replace the plumbing with something more durable, reliable, and freeze/break resistant. For some reason I have this idea that PEX is less likely (than PVC) to break if it freezes. It seems to me that as the ice expands it would push the fittings off the PEX pipe/hose rather than split sideways, and if it's going to freeze, that would be better and easier to fix than cracked PVC.

    Also, the cabin's water comes from a cistern about 100' feet away and 23' below the cabin. Currently the sucker line is a flexible black plastic line, about 3/4" to 1" in diameter, and I have this idea of replacing that line with large diameter PEX, sleeved inside of a PVC "conduit" (not sure what the right word is), with the idea that I could easily pull the line through the PVC if necessary, and also perhaps the PVC sleeve might help protect the PEX from freezing.

    Is PEX a better alternative than PVC for these purposes (under-house plumbing and the sucker line)?

  2. #2
    Moderator & Master Plumber hj's Avatar
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    The first consideration is that PVC is NEVER a good product to use "inside" any building, but you could have CPVC which is approved for that purpose. IF the PEX freezes at a fitting, it COULD separate, or the fitting could break, but if it freezes in the "middle" of a run, it will split if the pressure is beyond what the PEX can absorb. All the sleeve will do is insure that if the pipe breaks you will have to pull it out and replace it, rather than patch where it breaks.
    Licensed residential and commercial plumber

  3. #3
    DIY Member BillyJoeJimBob's Avatar
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    Also, I'm wondering about pipe diameter. Usually I see 1/2" PEX in houses, but I wonder if there is a reason to go larger? Same question for the sucker line. Would a larger diameter sucker line increase water pressure, water volume, reduced load on the pump, etc...? My sense is that if industry standard is 1/2", it is only because that that is the minimum that builders/contractors can get away with, and that (maybe) bigger is better.

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    DIY Member BillyJoeJimBob's Avatar
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    Quote Originally Posted by hj View Post
    The first consideration is that PVC is NEVER a good product to use "inside" any building, but you could have CPVC which is approved for that purpose.
    Thanks hj. That's also something I wanted to know about. I got a lecture about the difference between CPVC and PVC from a guy at Lowes and wanted to double-check if it was correct, that PVC was unsuitable for carrying potable water due to toxins leeching from the plastic into the water. Is there another reason to use CPVC, such as freeze resistance?

    What about the choice between PEX and PVC for this specific instance? Is there a clear "best choice" and if so for what reason(s)?

    I was in Home Depot yesterday looking at PEX fittings and they were charging about $6.00 each for them. Is there a better/cheaper alternative? I also saw some PEX fittings that looked like they were compression and made out of plastic (vs. metal). Given that the PEX tool was $100, would these be a better alternative?

  5. #5
    DIY Senior Member houptee's Avatar
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    The brass pex fittings (not shark bite style) are much less than $6 ea.
    Lowest cost method and easiest for DIYer is to use the stainless steel pinch clamps vs. the copper compression rings which require the more expensive tool.
    The pinch tool looks like large pliers and works on all sizes of pex pinch clamps so you only need that one tool.
    Look online for best price on the auction site that starts with E for pex pipe and tools or:

    $40 at Lowes
    http://www.lowes.com/pd_153553-61002...ool&facetInfo=
    $57 at Home Depot
    http://www.homedepot.com/p/SharkBite...6?N=5yc1vZbqlq

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    The size of the supply piping depends on the desired flow. 1/2" pex has a smaller ID than copper (it's closer to 3/8" copper). But, depending on what it is feeding, may be more than sufficient. The length and number of fittings affects the overall friction of a fluid through the pipe. 1/2" would not likely be sufficient except for one device. You may want 1" or maybe more from your supply point to the cabin where you could then branch off of it with smaller pipes for the individual fixtures. Pressure with no flow would be the same regardless of the pipe size, but then add flow, and friction comes into play. IOW, with no flow, the pressure would be the same with a fire hose verses a soda straw, but then try to actually use that water, the flow out of the smaller pipe is likely to be insufficient.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7
    DIY Senior Member houptee's Avatar
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    PEX cannot be exposed to UV light outdoors so keep that in mind for the main supply to the house.
    3/4 pex hot and cold feeding a pex manifold with 1/2 branches is pretty much the standard size used.

  8. #8
    Master Plumber master plumber mark's Avatar
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    the best pex on the market is wirsbo Aquapex....
    It will not break when it freeszes , I know this from personal experience

    we had a Diyer that had us plumb his house in Sept 05 , had the water on
    for them and they were supposed to have the heat on within a month... Instead
    they got into a fight with the hvac man and never got the heat finished... I found out
    about all this in Janruary.06...

    the people were totally clueless and i told them that their plumbing was probably ruined
    they left the water on and found that it had been flooding the place for a long while...

    but it withstood the freezing temps and I was able to salvage the whole system except for the
    copper stub outs for the water heater and water softener.....
    The copper froze and broke first and it sort of acted like freeze plugs in the system .. and I
    guess the rest of the system was not under extreme stress


    if you use aquapex , your risk is minimal...
    add a couple of copper stubs that would freeze and
    break first and your in good shape....


  9. #9
    DIY Senior Member houptee's Avatar
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    I used Rifeng PEX-b and Sharkbite PEX with same result, the copper sections froze and broke, the pex all survived no problems.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    PEX is flexible enough so that it will not be damaged if it is frozen...water expands about 1.1x its original size when frozen and that's much less than say Wirsbo pex is expanded to make a connection. Fittings, though, are a totally different thing. Depending on what freezes, you may not notice any problem other than the lack of flow, but if it freezes a fitting, all bets are off.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    DIY Member BillyJoeJimBob's Avatar
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    Quote Originally Posted by jadnashua View Post
    The size of the supply piping depends on the desired flow. 1/2" pex has a smaller ID than copper (it's closer to 3/8" copper). But, depending on what it is feeding, may be more than sufficient. The length and number of fittings affects the overall friction of a fluid through the pipe. 1/2" would not likely be sufficient except for one device. You may want 1" or maybe more from your supply point to the cabin where you could then branch off of it with smaller pipes for the individual fixtures. Pressure with no flow would be the same regardless of the pipe size, but then add flow, and friction comes into play. IOW, with no flow, the pressure would be the same with a fire hose verses a soda straw, but then try to actually use that water, the flow out of the smaller pipe is likely to be insufficient.
    I'm going to the cabin in a couple of weeks, and will get a more precise measurement, but the distance from cistern to cabin (with pump underneath) is around 100 ft. I'm calling this the "sucker line" and if someone can give me the correct term, I'd appreciate it.

    The sucker line is 3/4" of a shiny, smooth, continuous plastic from the late 1970's. I have a lot of trouble priming the pump and one reason is that there is a hose clamp connection about 8 feet outside the cabin about 8" deep in the dirt where it must have frozen, broke and someone repaired it with a male to male nipple and two hose clamps. I replace the two hose clamps the last time I was there with 4 of the highest-quality hose clamps I could find, with the idea that part of my problem with the sucker line is that the "pull" of the water wanting to go back downhill into the cistern was introducing air through this faulty hose clamped connection. The pump is about 20 to 25 feet above the water level of the cistern, so the pump is pulling 20+ feet up and @100 ft. laterally in a 3/4" 35 year old plastic pipe that is probably not even allowed by code anymore.

    This is the "big picture" and why I am thinking about replacing the sucker line with 1" or larger PEX. While it seems there are larger diameters available, one they are expensive, and two I wonder if the mass or "weight" of all that water wanting to slide downhill might be a bad thing, and maybe it would be better to keep the diameter of the sucker line at 1". Is there any benefit to going larger than this, and is that benefit worth the 100% or so increase in cost for the pipe?

  12. #12
    Test, Don't Guess! cacher_chick's Avatar
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    Black plastic polyethylene (P.E.) is commonly used in well applications, and is much less expensive than similarly sized PEX. It is most common to use 1" or 1-1/4" P.E. from the well to the pressure tank.

    When using P.E. one must make sure they buy the type that is listed and labeled for potable water use. There is cheaper stuff out there which is for irrigation.
    Last edited by cacher_chick; 02-04-2014 at 09:10 PM.

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    In the Trades Jerome2877's Avatar
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    Quote Originally Posted by BillyJoeJimBob View Post
    I got a lecture about the difference between CPVC and PVC from a guy at Lowes and wanted to double-check if it was correct, that PVC was unsuitable for carrying potable water due to toxins leeching from the plastic into the water.
    No, it is because of the temperature rating of PVC that makes it unsuitable for use inside the home. Many supply lines from the meter to the house are PVC as well as many city mains.

    Don't listen to the guys at lowes!

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    CPVC is stronger, is more heat tolerant (than pvc) and has smaller pores and a smoother surface making it better at potable water supplies and particularly when used for hot water where regular pvc can begin to erode over time.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #15
    DIY Member BillyJoeJimBob's Avatar
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    Quote Originally Posted by cacher_chick View Post
    Black plastic polyethylene (P.E.) is commonly used in well applications, and is much less expensive than similarly sized PEX. It is most common to use 1" or 1-1/4" P.E. from the well to the pressure tank.

    When using P.E. one must make sure they buy the type that is listed and labeled for potable water use. There is cheaper stuff out there which is for irrigation.
    So can I assume from this that "P.E." is still being used? Is there a compelling reason to use PEX instead of P.E.? I don't like or trust the hose-clamped connections, and it's possible that there are other repairs in the line underground which may be introducing air into the line. It's REAL hard to prime, and even when running it feels weak and flabby, and I can't tell if that's due to the suction height or possibly air in the sucker line from leaking hose-clamp connections.

    So, if I dig the old line up (it can't be too deep as the mountain is granite) what recommendations are there to replace it? Originally I thought P.E. was bad and PEX was good, but if P.E. is good enough, is there a way to improve what I've already got beyond replacing a broken line with a continuous one? What about the idea of running the P.E. inside of a PVC conduit? One option I think about is installing a submerged "pre-pump" inside the cistern to help push the water uphill to the (primary) jet pump. So I was thinking I could run a 110 or 220 line inside the PVC conduit alongside the P.E. or PEX line.

    Is there any reason to NOT do this? Is there a better way? Also I wonder about heating this line. Is there some kind of tape that can be run that turns on whenever the temperature falls below "x" degrees?

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