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Splice or one piece? (PEX)

I am planning on putting in hydronic heated floor in my shop when it's built.. no dirt work yet, now is the time to do it.

Without waiting for shipping - only available lengths of pex are in 100 ft rolls.

Should I wait and get longer spools or can the pex be successfully be spliced in the concrete??

I can do the crimp fittings if those will work. My main concern is the effect of the concrete on the brass / copper splice hardware.

Waterproof or otherwise insulate them, or just make several 100' heating loops.

One more question, total square footage is 1200' about how much tubing should I be looking at to purchase??

Thanks in advance

Robert Avery


  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    sounds like

    you are considering non-barrier pex.

    if you have a really small shop, or very mild winters, and are using a water heater to power it, maybe that's not a horrible idea, but in nearly all cases I would encourage you to use oxygen barrier pex to keep your future heat source and water additive options open.

    which would mean waiting.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • furthur
    furthur Member Posts: 25
    what he said...

    Non o2 barrier pex never works out economically if you figure a bronze circ. pump, and if you need a heat exchanger for the boiler...forget it.

    Your best bet for estimating pex length is run the heat loss and find out how many BTU's/sqft you need, BUT...running 1/2" pex in concrete for a shop, built to current standards, you will probably be ok to run every 12", 300' max each loop, so 1200' total, 4 loops.  You could go longer loops and maybe wider spacing with 5/8", or even 3/4", and in a shop that would be fine, but you will feel the difference as uneven heat across the floor surface.  My garage has 1/2" every foot, and you can feel the temp difference when barefoot, BUT, I have a concrete garage floor that you can walk barefoot on all day...

    Insulate and vapor barrier under the slab...

    Just a doit yourselfer, learning the hard way, as usual.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013

    larger tubing diameters do not allow for wider spacing to maintain the same output.

    larger pipes just allow for longer loops. heat output is nearly identical.

    that said, you can often go wider than 12" o.c. in shops. But absent any real design work, I wouldn't chance it.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • CMadatMe
    CMadatMe Member Posts: 3,066
    Slab on Grade

    Generally slab on grade/concerete application calls for 12" on center. Max loop length for 1/2" pex to and from the manifold is 300'. To tell you 12" on center is what you want to do would be wrong without a heat loss and radiant design. What did you plan on for insulation under and perimeter for that slab? What type of shop is this? Is the system going to have antifreeze in it? Are we keeping it 70 or our we looking to take the chill out? Are there garage door areas? Is so you would want to be tighter maybe 9" on center in those areas and get back out to 12" on center as you move towards the center of the floor. Again, heat loss, heat loss and insulation is your best friend.

    I would never splice tubing in a slab.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Slamdvw82716
    Slamdvw82716 Member Posts: 5
    more info.

    Thanks for the information.  As luck would have it, they're moving faster on the digging and forming that I planned..  I knew once they got started it would go like a wild fire.

    I did have a little forethought and bought enough 2" pink foam insulation to do under the entire slab, and 4' out from the edges.

    A friend of mine just completed a project, and gave me about 500' of barrier PEX, the remainder will have to be non barrier.  It's whats available on such short notice.

    Another post I had, I was thinking about using that black PE tubing that's used for irrigation - but was convinced otherwise.

    For temps, I was thinking just taking the chill off.  One garage door, two man doors.

    So far, just the floor is planned.  After the floor is done, I'll have to wait till finances allow to build the building.  But 2x6 walls, hopefully insulated as well.

    Antifreeze, more than likely.  There will probably be days or so where I won't want to run the heat - depends on availability of fuel ( planning on building a waste oil fired boiler ).  Maybe coal, I am in Northeast Wyoming.

    Thanks again for the info.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    glycol and non barrier pipe

    is not a good mix. You'd be well served waiting a day or two to get o2 barrier pipe on hand.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Curious ....

    Rob, you said "glycol and non barrier pipe

    is not a good mix. You'd be well served waiting a day or two to get o2 barrier pipe on hand."

    I have seen hundreds of snowmelt systems that were set up this way, and haven't seen any issues. Are you seeing something I'm not seeing?

    Just to be sure, I am in your camp regarding the use of O2 barrier tube. Just wondering if you are seeing something I'm not. The systems I am seeing are with corrosion inhibited glycol. If that protection package goes South, all bets are off!

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • zacmobile
    zacmobile Member Posts: 211
    barrier pex

    where are you located? I find it kind of odd that you would have that much trouble locating oxy pex, every pluming supply place i've ever seen stocks it, (even where I am which is relatively in the sticks) even the big box stores like home depot, surely there must be somewhere within a reasonable driving distance?
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    the last information I had

    was that oxygen diffusion reduces the lifespan of the inhibitors in glycol, so that the PH increases more rapidly over time.

    oxygen diffusion is less in low temperature situations and in concrete. but I would consider it bad practice at least to use non barrier pipe and glycol. that's one of the primary reasons I have for using o2 barrier pipe; it's very hard to predict that a system will *never* need glycol, even though I avoid it like the plague.

    snowmelt is probably the safest possible situation for that combination though I would think. And I don't have the o2 diffusion math to hit this topic with real rigor, so I could be wrong.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • Slamdvw82716
    Slamdvw82716 Member Posts: 5

    I am in Gillette Wyo.  Home Depot and the other plumbing supply stores in this area do not have barrier pex. 

    Now, if I could black poly pipe - how many miles do you need?  The CBM ( Coal Bed Methane ) industry here buries it by the mile.

    Hydronic heat don't seem to be that popular around here.
  • kcopp
    kcopp Member Posts: 3,698
    One chance...

    to do it right... get the right stuff. Then you can sleep better and not have problems down the road.  In this day and age FedEx or UPS should be able to get the product to you w/ in a day or so.

    Are you on a very tight budget? has pretty good pricing... although I prefer uponor for radiant. kpc
  • Slimpickins
    Slimpickins Member Posts: 323

    There's a Winnelson in Gillette. Have you checked there?
  • furthur
    furthur Member Posts: 25

    kcopp, pretty sure that store does still sell hepex, though it's been awhile since I ordered.

    Slam, wait for barrier's really hard and expensive to do it over, way too cheap and easy to NOT do it now.  I'm currently working on some retrofit...

    good luck
    Just a doit yourselfer, learning the hard way, as usual.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Why use glycol...

    Rob, I get your point, and agree for the most part. You incorrectly stated the pH would go up over time. It won't. It goes down, and starts eating metal components. I suspect that is what you meant to say, but just flipped it. I get it. You get it, and now anyone reading this gets it :-)

    If it is a closed loop system, AND it is operating at a real low temperature, AND the fluid is being tested and corrected annually, then and only then would it be acceptable to me. And we all know, annual service is a dream...that can quickly turn into a nightmare when not performed.

    To anyone else reading this and wanting to know some stuff about non barrier tube, there are three prescriptive methods for allowing its use, none of which I agree with due to seeing it misused and failing in the field.

    One is to isolate the non oxy barrier tube from ferrous components with a heat exchanger. Adds more expense than it would have cost to use barrier tube in the first place, and places the burden of maintenance on the HO.

    Second is to require all non ferrous components in the system. Even more expensive than the above option, and just because you are using a copper fin tube boiler does not mean that the mild steel tube sheets the copper is rolled into will not fail.

    Third is to require annual fluid maintenance. Yeah right...

    As for the use of glycol, I will only use it if one of three conditions are present. One is the possible loss of fuel with no one around to notice (LP, or oil in a remote, unmonitored home).

    Another is the possible loss of electrical power in the same situation, no one there to realize trees blew down, taking out the power lines serving the dwelling, and the third is structural preclusion. That being an overhang situation with tubing in the bays below the floor.

    Oh yeah, forgot to add snowmelt, but that should be pretty obvious, I hope...

    Regardless, if for what ever reason you DO have glycol in your systems, you do NOT want an automatic makeup connection to a potable water system that can (and will) inadvertently dilute the glycol to the point that it is non existent. You won't know it has happened until it is too late.

    If you have glycol, it DOES require regular maintenance.

    If you use non barrier tube, the fluid MUST be maintained.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
This discussion has been closed.


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