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CPVC in hydronic heating system

Chuck_17 Member Posts: 138
Any experience using CPVC piping for hydronic heating systems?

It is commonly used for domestic hot water?

Lets say the heating system is designed for below 180 deg. (say 160-170ish).

Additional issues for a heating system?

Higher temperatures and associated expansion?


Oils (from pumps or whatever)?


  • kcopp
    kcopp Member Posts: 4,264
    I remember....

    a few years back seeing a picture here of someone doing just that over in China.... Oxygen would be the biggest problem.

    It semi fragile nature another.

    With pex being so easy to work with cpvc doesn't make sense to me.
  • Wethead7
    Wethead7 Member Posts: 170

    CPVC does not allow Oxygen travel through the wall of the tubing. The design of the heat system should be lower water temperatures. I you keep the supply temperatures under 150. Things should work well. The lower temperature emitter system would drive up overall efficiency.
  • Gordy
    Gordy Member Posts: 9,537

    Would be the question, unless your sitting on a mountain of free stuff. Along with what Kcopp points out. Pex is a much easier pipe to work with.
  • superdave
    superdave Member Posts: 155
    look at this

    I just looked at a system that has 60 unit all pipped with CPVC on heating side with slab on grade radiant
  • superdave
    superdave Member Posts: 155

    They are having  problems.
  • superdave
    superdave Member Posts: 155

    What are you thoughts
  • superdave
    superdave Member Posts: 155

    low bidder or just what is left on trucks.
  • superdave
    superdave Member Posts: 155
    55 plus living

    I think should start over????
  • superdave
    superdave Member Posts: 155
    last one

    last one
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840

    Wethead7, I am hoping there was a typo in your statement. To the best of my knowledge, there is no oxygen barrier PVC or CPVC on the market.

    Got reference articles/stories?

    As others have said, it is not a standard practice, and I suspect there are economic rea$on$ as to why. It looks to me like a handyman took on the job and didn't trust his soldering skills, but knew how to do plastic fusion/solvent welding.

    I see green pumps, which are cast iron. I suspect that rust never sleeps on this job…

    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.
  • Wayne Heid
    Wayne Heid Member Posts: 49
    CPVC and oxygen barrier


    While I totally agree that CPVC is inappropriate for hydronic piping, it is an approved material for hydronic systems in the New York / ICC mechanical code. Charlotte Pipe has this to say about oxygen diffusion in their Plastics Technical Manual:

    CPVC CTS FlowGuard Gold does not typically require an

    oxygen barrier. In accordance with ASTM D 2846, CPVC

    CTS is manufactured as a solid-wall piping system and is

    not manufactured in a cross-linked or co-extruded process

    like other materials that are prone to oxygen permeation.

    Unlike CPVC, some cross-linked systems used in applications

    such as hydronic heating require a layer of aluminum to be

    present to stop oxygen diffusion through the polymer matrix.

    With regard to oxygen permeability of a CPVC system, the

    following data should be considered:

    1) The oxygen transmission rate in CPVC at 73°F (23°C) is

    approximately 7.2 cc/(m2/day).

    2) The oxygen permeation coefficient in at 73°F (23°C) is

    approximately 180 cc/mil/(m2/day/atm).

    3) The oxygen diffusion coefficient in CPVC is approximately

    6.25e/9 cm2/sec.

    They go on to say that only schedule 80 should be used on hydronic systems.

    As a practical matter, a CPVC piping system would require much more pipe support than most are willing to provide. They require special male adapter fittings with brass threads. Flow rates are reduced because of the reduced internal diameter. And, to the trained eye, it just looks amateurish (if that's a word).

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    edited April 2014
    Thanks Wayne...

    I love it when someone causes me to think in different ways and to do some research.

    From MR. PEX' web site, I found:

    What was the result?

    What does DIN 4726 actually say?

    The last page of the standard includes explanations, so the basis becomes clear. Following is a translation of the section describing their considerations: “Experience from heating systems have since long established that corrosion levels in hydronic systems with ferrous metals are acceptable at the level one exchange of the system water (to fresh water) per annum. This corresponds to an oxygen amount of 0.05g/(cu.meter * day). An “allow- ance” of doubling this amount is given (allowing for measurement inaccuracy) to make the “tightness require- ment” to be 0.1 grams (per cubic meter and day). Plastic tubing shall meet this requirement after having been thermocycled between 70°C (158°F) and 20°C (68°F) for 28 days while tightly coiled, and a final permeability measurement then carried out at 40°C (104°F) (repeated 3 times). Typically, non-barrier plastic tubing allows about 5 grams to enter; 50 times more than allowable. For tubing that does not meet this permeability require- ment either of following measures must be taken:

    • corrosion-resistant components must be used either in the

    whole system or at least in parts which come into contact

    with water flowing through the plastic pipes.

    Here is the full article: http://www.mrpexsystems.com/pdf/Diffusion.pdf

    So, if my interpretations are correct, CPVC does allow significantly more oxygen into a system than would a barrier oxygen product, and all wetted components should be dealt with accordingly. This will require a regular and continuous monitoring and adjustment of water quality (corrosion inhibitors, oxygen scavengers, pH etc).

    Even though the code says it's OK to do it, doesn't mean it's a good idea. Remember, most codes allow the use of open combination space heating/DHW systems with a single fluid…

    Thanks for posting the information you did.

    Let's ask superdave. What KIND of problems are you seeing in the field that brought this to your attention? Corrosion, joint failure, pipe failure, pipes sagging, leaks?

    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.
  • Snowmelt
    Snowmelt Member Posts: 1,394

    Just last year I did a job where it was the opposite

    Was a navian water heater job and the newer condensation had a female thread 1/2 inch, I thought it was barb, it was Saturday 2 pm I just finished everything I didn't want to come back from job. I grabbed 2 copper male adapters 1 tee 1 elbow (2 units), and a few short like 2 feet of 1/2 copper and ran the condensation in the sump pump pit.
  • SWEI
    SWEI Member Posts: 7,356
    Non-barrier polymer pipe

    still has a place in the ecosystem as long as it is deployed properly.   Aquatherm does not have an O2 barrier, but as long as it's used mostly for larger distribution lines (where most of us find it makes the most sense anyway) there should not be a problem.  http://www.aquatherm.com/downloads/bulletins/201308B-AQTTB-Oxygen-Permeation.pdf

    My own experience with combination systems using hePEX and Aquatherm with large numbers of steel panel radiators is that we see a bit of fine magnetite (aka general corrosion) during the first few weeks of operation as the system de-airs itself.  Once the system is fully purged of air, we turn off (or remove) the autofeeder and verify that pressure is maintained.  At that point, the amount of magnetite decreases, eventually stabilizing at a low level.
  • RobG
    RobG Member Posts: 1,850

    I agree Superdave, time for a re-pipe. I love the idea of not using any of those pesky isolation valves however, it really helps on improving flow rates of the system.

    It's interesting on Wayne's post from Charlotte pipe, They start out saying that Flowguard Gold CPVC in cts size is okay for hydronic, then at the end say only SCH80 should be used. That makes no sense as cts and SCH80 are two completely different animals. And we wonder how jobs like this get installed, much less approved. It doesn't look like they even  used the Flowguard gold cement.Go figure!!
  • Chuck_17
    Chuck_17 Member Posts: 138
    piping mains and large branches

    Thanks for the comments.

    PEX is great but I was thinking of application in a more conventional system like baseboard or fan coils (in an older building with higher heat loads).
  • Wayne Heid
    Wayne Heid Member Posts: 49
    Confused by conversion


    Now I'm confused. In attempting to compare the oxygen permeability rates of CPVC to barrier PEX, I look at the examples from our two posts and I don't see how you come to your conclusion that CPVC allows significantly more oxygen into a system than barrier PEX. Actually, I don't see how any conclusion can be drawn (unless my math is rustier than I thought).

    The specs are apples to oranges. The DIN 4726 spec refers to grams / cu meter / day while the Charlotte CPVC specs refer to cubic centimeters / milliliter / square meter / day. Grams is a measure of mass and cubic centimeters is a measure of volume and not comparable. The Charlotte spec also refers to square meters vs. the DIN 4726 reference to cubic meters.

    I want to be able to definitively agree with you but the data we're looking at here doesn't appear to support the conclusion we'd like to make. Am I missing something?

    And thanks for the link. It was interesting reading.

  • Canucker
    Canucker Member Posts: 721
    Very comparable

     1000 L is 1 cubic meter and weighs 1000kg. 1 cubic centimetre is equal to 1 millilitre which also weighs 1 gram. Conversions and comparisons should be easier to do now.
    You can have it good, fast or cheap. Pick two
  • superdave
    superdave Member Posts: 155
    What would you do???

    When I have installed slab on ground I have installed antifreeze to prevent freeze up. I also know if you put it into CPVC it will breakdown the piping and fittings. I don't use 100% but i think it is good to have some in it.  The boiler are having problems and you know if you touch it you own it.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Leave it to marketing...

    Wayne, I hear what you are saying. The DIN standard is THE standard, but leave it up to a bunch of marketing guys to take those numbers and "massage" them to make their product look superior.

    Bottom line, we ALL have to drive on the same highway, and we ALL are SUPPOSED to follow the same direction signs on said highway. When I saw your spec using CC's, I did a conversion search and found that they were the same. I forgot to look at the rest of the measurements given, because I assumed we were all driving on the same highway, hence playing by the same rules.

    The true bottom line is this. All plastic tubing has the propensity to allow oxygen transfer through its walls. Some more or less than others, and most differently at different temperatures of operation. Plastic tubing can not stop the migration of oxygen through its walls, and mother nature in her constant effort to balance everything out WILL see sure to it that imbalances in oxygen on either side of the tube walls do not happen. Even in cases where a metallic oxygen barrier is used (PEX-AL-PEX), she WILL find a way to balance out the O2 on both sides of the pipe. She can and does do it with all metal pipe systems, and she sure as heck can and will do it with plastic piped systems. It's the nature of Nature.

    This is the whole reason that the DIN standard for oxygen diffusion was developed, so that the consumer could see what their selected tubing does in comparison to other tubes on the market. It all boils down to this. Plastic tubing (pick your type) does allow oxygen to transfer through its walls, and if the system is not designed correctly and maintained properly (non ferrous components or continuous fluid testing and adjustments) something is going to give up the ghost to the omnipresent oxidizer, oxygen.

    But as Copper Head Ken Secor use to say on a regular basis, "Marketing can overcome real world engineering every day of the week", or something to that effect...

    Reminds me of claims made by tankless water heater manufacturers. "MY unit can generate XXX gallons per hour of hot water" without giving the temperature rise of said water. The bigger the XXX number, the better they look to the consumer. In reality, its some straight forward math, and if all manufacturers were required to give the information in hourly GPH recovery capacity per degree F rise based on a 100 degree F rise, the marketeers can't mess with the math to make their product look better, and then the playing field is level, and the truth comes out.

    By the way, there is a movement underfoot to make this fixed degree F rise a requirement for reporting the output capacity of a given tankless water heater. (UMC 2014). But I digress…

    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.
  • icesailor
    icesailor Member Posts: 7,265
    PVC/CPVC Cleaner:

    And cleaner is non-existent. You can tell in an instant if the pipe was cleaned. Most of what I see here isn't cleaned and what I see where I now live has never seen a cleaner brush. Just slather some purple glue on wet and dirty pipe and shove it in so the purple glue sticks out on the pipe.
  • Ross_24
    Ross_24 Member Posts: 82
    edited April 2014

    I agree superdave, you've got a tear out and redo on your hands. That or nothing.

    Is that a taco mixing valve going straight into a T&P? In picture #3.
  • M Lane
    M Lane Member Posts: 123
    FloGard Gold

    Out here its used in multi-family construction b/c its the cheapest material around. I have seen it used with what they call aquaterm style heating systems, where the water heater has a coil for heat water,operates at 140. If I ever put that stuff in for a client, I would hope none of my buddies or peers would ever see it. I don't trust the glue at all.

    If I were an inspector I would want to see documentation from the manufacturer confirming it is designed and approved for a 180* application. And if they do, how long do they warrant the material? Compare that to Uponors warranty.
  • M Lane
    M Lane Member Posts: 123
    That said....

    I used to work for Denver's biggest mechanical contractor. The schedule 40 style of CPVC (the gray stuff) is now commonly used for condenser water, domestic water (both hot and cold), and chilled water systems in our most recently built towers. I would have far less of a ethical problem using that stuff for manifolds or other non-concealed applications. But still, if your'e talking about straight up 180* set point boiler water, I would stick to steel or copper for manifolds and Al-pex or Wirsbo as options only for distribution lines. We have things such as 'industry standards', if they slip too far towards cheesy we will all lose control over the trades.
  • Youngdogs2
    Youngdogs2 Member Posts: 14
    PP pipe only as it will last for 100 years or more. CPVC is a great material, but not for heating applications. Environmental Stress Cracking will occur with any petroleum based material it comes in contact with...(Oils, Thread sealants that have petroleum based compounds, etc.....)
  • superdave
    superdave Member Posts: 155
    Hi All sorry for the delay. I forgot to say these boilers do not have an auto filler kit on them. I have replaced one pump, about 6 Ex tanks that are part of the boiler and 6 PSI relief valves. The biggest call I get is low water I don't know if its from the CPVC or just know way to bleed out system right and are works its way around.