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Importance of CTS?

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  • Importance of CTS?

    Pex has a smaller inside diameter than copper. Why did pex manufactors decide that the outside diameter was more important than the inside diameter?
    Buy cheap, buy twice.

  • #2
    Re: Importance of CTS?

    I think the best way to figure out the answer to your question would be to contact a PEX manufacturer, otherwise one would just be guessing.
    Proud To Be Union!!

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    • #3
      Re: Importance of CTS?

      Maybe the design of the connection?

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      • #4
        Re: Importance of CTS?

        Originally posted by gear junkie View Post
        Pex has a smaller inside diameter than copper. Why did pex manufactors decide that the outside diameter was more important than the inside diameter?



        Because in order for PEX to be competitive and commingle properly with copper, it has to be able to mate size for size in order to accomplish that.


        The inner diameter is lessened given the structural quality that is needed to maintain effectiveness.


        IOW, They'll never make PEX as thin as copper as it will not perform to meet most codes.
        Northern Kentucky Plumbers Twitter Feed | Plumbing Videos

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        • #5
          Re: Importance of CTS?

          My guess is that PEX morphed from tubing. Typical plastic and steel tubing as used as air lines etc. in industrial equipment has always been sized in OD x wall thickness. This way you can use the same fittings for thick or thin wall. I realize that pipe is the same way - the ID of 80 is less than the ID of 40, both with same OD, but for some reason (my guess is different groups set the standards years ago) Tubing has always been sized in nominal OD with the fractional sizes being the standard.
          Last edited by JTROANOKE; 09-10-2008, 07:18 PM.

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          • #6
            Re: Importance of CTS?

            To accommodate existing compression sizes.
            Mike

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            • #7
              Re: Importance of CTS?

              To match the drillbits.

              I can't remember the code but at one time the minimum supply for a structure here was 3/4" with a schematic showing that the ID cross-hatch of pipe and fittings must be a minimum of 3/4" which 3/4" PEX cannot do. Meaning, of course, that every main supply in PEX should be a minimum of 1". Including the main shutoff.

              I always wondered how & why this was overlooked as I see 3/4" PEX mains all the time.

              J.C.

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              • #8
                What do all them markings mean?

                PEX Tube Markings

                In the U.S., PEX tubing will bear several of these marks:

                Manufacturer's name and product name.

                NSF-61. This mark indicates that the pipe meets NSF/ANSI Standard 61 for health requirements.

                NSF pw. This mark indicates that the pipe meets both NSF-61 as well as NSF/ANSI Standard 14 for performance, strength and quality control.

                NSF rfh. This mark indicates that the pipe only meets standards for radiant floor heating.

                ASTM F876 and F877. These marks indicate that the product meets requirements for dimensions and ability to withstand pressure and temperature.

                CSA B137-Series 5. This is the Canadian equivalent of the above U.S. standards.

                CTS-OD. Copper Tubing Size, Outside Diameter Controlled. This means that the PEX tubing's outside diameter is manufactured to be the same as the outside diameter of the same size copper tube.

                SDR 9. Standard Dimension Ratio. Refers to the thickness of the PEX tube wall. This is the standard PEX thickness, where the wall is 1/9th of the outside diameter of the tube.

                ASTM F876 Standard Specification for Crosslinked Polyethylene (PEX) Tubing
                ASTM F877 Standard Specification for Crosslinked Polyethylene (PEX) Plastic Hot- and Cold-Water Distribution Systems
                ASTM F1281 Standard Specification for Crosslinked Polyethylene/Aluminum/Crosslinked Polyethylene (PEX-AL-PEX) Pressure Pipe
                ASTM F1807 Standard Specification for Metal Insert Fittings Utilizing a Copper Crimp Ring for SDR9 Cross-linked Polyethylene (PEX) Tubing
                ASTM F1960 Standard Specification for Cold Expansion Fittings with PEX Reinforcing Rings for Use with Cross-linked Polyethylene (PEX) Tubing
                ASTM F2023 Standard Test Method for Evaluating the Oxidative Resistance of Cross-linked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water.
                ASTM F2080 Standard Specification for Cold-Expansion Fittings with Metal Compression-Sleeves for Cross-linked Polyethylene (PEX) Pipe
                ASTM F2098 Standard Specification for Stainless Steel Clamps for Securing SDR9 Cross-linked Polyethylene (PEX) Tubing to Metal Insert Fittings


                See http://www.pexinfo.com/#tubing for more.
                Last edited by Bob D.; 09-10-2008, 09:25 PM.
                ---------------
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                • #9
                  Re: Importance of CTS?

                  Look at copper - whether it's K, L, or M, it has the same outside diameter. They didn't say, "Oh, we have to have the same inside diameter!" Think what a fitting nightmare that would be.

                  Then think about how water saving has come into play - faucets and valves that deliver a fraction of what some old ones did. The inside diameter can be smaller and still supply more fixtures.

                  I remember one customer who had an ancient shower valve with 3/4" inlets. She insisted that if I put in a new one, it had to deliver water as quickly as the previous one. Right. I drove off and never heard from her again, thankfully.

                  As for drill bits - I've used a number of sizes. It used to be that a 1-1/8" was pretty standard when plumbing with copper, but when the new pipes came out, it became common to use 1-3/8" for the isolators/insulators that were used to protect the pipe. So that ain't it.

                  I liked Polybutylene pipe - it had a much larger inside diameter while retaining the CTS.

                  Heh - you should see the mess I fished out from under a trailer this week when the earlier HO decided to fix it himself. Saying it leaked was like saying Niagra is just a waterfall.

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                  • #10
                    Re: Importance of CTS?

                    so sharkbite fittings could be used for connecting copper and pex

                    but realistically the 1/2'' pex is 5/8'' od, same as copper and compression angle stops will interchange might have a little to do with it

                    rick.
                    phoebe it is

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                    • #11
                      Re: Importance of CTS?

                      The OD of PEX pipe is based on the OD of copper tube size. The exception to that would be be K itec as it has it's own Standard (ASTM F1281).

                      Mark
                      "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                      I never lost a cent on the jobs I didn't get!

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                      • #12
                        Re: Importance of CTS?

                        Originally posted by PLUMBER RICK View Post
                        so sharkbite fittings could be used for connecting copper and pex

                        but realistically the 1/2'' pex is 5/8'' od, same as copper and compression angle stops will interchange might have a little to do with it

                        rick.
                        Except as noted above.

                        Mark
                        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                        I never lost a cent on the jobs I didn't get!

                        Comment


                        • #13
                          Re: Importance of CTS?

                          Most angle stops I've seen( out side of Massachusetts ) are compression!
                          Mark(Utah) No need to foot note me. I know you are saying DAMN he's right
                          Mike

















                          If you take this too seriously you need medication

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